Contesting information sign for passers by

Most of us that operate portable in any way will no doubt have had interested people come to ask us what what we are up to. My portable operations these days are almost exclusively contesting and single op so I don’t really want to break off a pileup to answer questions so I decided I would make a contesting information sign for passers by answering most of the questions before they ask them! I have found it to be very effective especially when I am tent portable on a mountain summit where there is a fair amount of walker activity. Often when I am in the tent listening around the band before the contest kicks off I can hear one person of a group reading out the card to the rest of the group. It’s been a great help. You may have even seen it in one of the Practical Wireless magazines in the PW 144MHz QRP Contest results write ups.

I printed and laminated it then peg it out with tent pegs from the pound shop between the summit and my tent:
contesting information sign for passers byIt’s survived some pretty hairy and wet weather so far. I also have another one for car portable that I put in one of the windows (doubles as a sun shade in the summer evenings!)

A few people have asked about doing one themselves so I have add below a Word DOC file and DOCX file (both ZIPped up) for you you use as a start point for your own version, you can just change the images and wording a bit to suit. Just needs a few tweaks to make your own contesting information sign for passers by to suit your own situation.

What exactly are we up do.DOC

What exactly are we up do.DOCX

Have fun and spread the good word!

If you found this useful, I’m always up for a coffee…
https://g1ybb.uk/buy-me-a-coffee/

Welcome to your new callsign. Now what?

Welcome to your new callsign. Congratulations on getting your shiny new callsign! And welcome to the Amateur Radio hobby. You may be wondering what to do with it now you have it! The foundation training cannot cover even a small part of the many facets of the hobby so I thought I would share a few of my thoughts, experiences and some of the threads in radio that I am aware of. There are many more I don’t! This is a hobby where the World literally is your oyster.

The facets I mention below are no particular order other than they are the things  I thought of.

Online Callsign Databases.
A great place to start is to get your new callsign registered on the online lookup sites. This is free and many people will look you up when they hear you on the radio, either manually or automatically with their logging software. The most used site is probably https://www.qrz.com but I would also recommend setting up accounts on https://www.hamqth.com and https://www.qrzcq.com as well. HamQTH and QRZCQ you just sign up with your callsign, on QRZ you need to make an account with your callsign as the user name and post to be added to the database forum Add My Call Sign to QRZ – Database Helpers Forum.

The following images are my entries on those three sites:
G1YBB page on QRZ
G1YBB page on HamQTH
G1YBB page on QRZCQ
Locator squares.
You will notice on the HamQTH and QRZCQ pages my locator IO82PA is stated. It’s very handy to know that and state it on your profiles. All or part of it is used in contests and data modes and grid square collection (more later on that).
To find it is really easy now with many web based help pages. I use this one:
https://k7fry.com/grid/?qth=IO82PA&t=n
Clicking that link will take you to my locator square as an example, but you just need to zoom & drag the map to your house, click the map on it and then use the first 6 characters (as a rule 6 is plenty). For example if I lived in Ross-On-Wye and clicked my house there a box pops up containing my house and tells me the locator is IO81RV09 so I would use IO81RV:
maidenhead locator map

Another square worth knowing is your WAB (Worked All Britain) square as you may be asked this. This is just the 4 figure OS grid reference of your location. Again the internet makes this dead easy to find. On this site:
https://www.bnhs.co.uk/2019/technology/grabagridref/gagr.php#map
I scroll the map again to my house in Ross-On-Wye, click the button “Get the mark” on the right hand side of the page and drag that to my house. Tick the “10km square (yellow)” tick box on the top right side of the page and your WAB square is shown, here it’s SO62:
WAB square finding mapYou are now pre-armed with information that sometimes catches out new hams that haven’t been told about it.

Logging.
I am a big fan of computer logging. It’s an easy and efficient way to log your QSOs. There are many advantages to this, many linked to some of the activities below. We hams like to spend all our money of radio stuff so some hams generously make free logging software available. I like and use one called Log4OM https://www.log4om.com/
This is very rich in features, too many to go into here, but I did write some pages on setting it up for portable operating, much of which is applicable to just setting up for your basic callsign:
https://g1ybb.uk/portable-logging-with-log4om-and-online-log-sites/

Here is a screen grab of Log4OM. I have heard a station PE1EWR on air or he called me so I have put his callsign in the box. The software has looked him up on qrz.com and has filled in his name and locator for me and also pulled down the photograph he has on qrz.com. Also it is showing me where in the world he is and a closer zoomed in map of his location, based on his given 6 figure locator. You can see why your locator is an extremely useful piece of information. From that locator Log4OM is also telling me Frank is 434km from my house (really it’s centre to centre of our locator squares):
Log4OM main screen
Log4OM can also upload your QSOs to the online logging sites automatically, even in real time as you log the QSOs, or at a later date from imports from other software like for example contest logging programs. Most of these are mentioned in my link above on Log4OM setup.

QSLs and eQSLs.
Not everyone’s cup of tea but many people like to exchange and collect QSL cards (confirmation of QSO) as the final act of completion of a QSO or to confirm a country or state for awards, or just because they like to do it. These historically are paper, like postcards but are also now widely done in digital form via the internet known as eQSLs.
As posting actual cards to many places would be expensive all the radio societies around the world run a service called the QSL Bureau. You can send QSL cards in bulk to you local bureau and they will distribute them around the world and the Bureau at the destination end will send them to individual hams. It is a very slow process but is a good option if QSL cards appeal to you. Personally I don’t collect them BUT as people do like to collect QSL cards if they send to me I will always reciprocate. Here is a batch of cards I received recently:
QSLs received via buroAnd here is a batch of mine before going to the bureau:
QSLs sending via buro
For UK hams to make use of the bureau you need to be a member of the RSGB. The bureau information is here:
https://rsgb.org/main/operating/qsl-bureau/

eQSLs are a much quicker process and can sometimes be exchanged literally within seconds of a QSO if both stations are logging online and uploading the QSOs in real time to the eQSL sites. Log4OM can do this. The main ones I use for eQSLs are eQSL https://www.eqsl.cc/qslcard/Index.cfm and HRDlog https://www.hrdlog.net/
A couple of sample EQSLs I have received:
J69DS eQSL
JA7NGE eQSL
Ok behind the sceens type of stuff out of the way, we need a radio!

Radios.
This has to be the most commonly asked question. What radio should I get that I can afford. Or another classic is “what is the best radio to get?”.
There is no answer to that question really without knowing a budget and interests. But you may not yet have found your radio interests so the answer is almost impossible to know.

My advice is nearly always to buy a multimode radio if you can afford it. This means you can access FM for simplex and repeater QSOS like you would on the seemingly ubiquitous FM handheld but also opens up that world of other opportunities like SSB and CW, data modes, basically everything. For those who want an FM handheld I personally usually advise getting one of the really cheap Baofeng ones. The keyboard warriors will slate these but I have had no issues with mine and for only a few tenners you can be on 144/432MHz FM and save more tenners for a multimode!
Baofeng UV82HP hand heldMultimode radio wise there is a vast assortment. For a first time radio I usually recommend a secondhand shack-in-a-box radio like a Yaesu FT857D or FT-897D. These have all the HF bands, 144MHz and 432MHz in one small unit and allow you to access all the most active bands and literally work the world on HF even with 10W on a foundation licence. Secondhand they will be in the reach of most budgets, probably starting around £350 and upwards. Whilst I now have dedicated HF radios and VHF/UHF/SHF radios I still love my FT-817 and FT-857D for certain portable operating where size is paramount. There are newer shack-in-a-box radios that have better interfacing to a computer such as the FT-991A.
Yaesu FT-857D multimode shack in a box

Join your local club.
A great way to pick up tips, learn new things and even get on the air before you have your own radio gear is to join your local club. Admittedly as I type this in the middle of the Covid19 pandemic it’s not as easy as usual but many clubs are having meetings via Zoom etc. Many clubs have a club station that (in normal times) can be operated by members and meetings that ntroduce you to new things. There is a club finder tool on the RSGB website:
https://rsgb.org/main/clubs/club-finder/

FM Repeaters.
These are very often most people’s first experience into amateur radio. Most areas have a local repeater in the vicinity that can be reached with a cheap hand held radio like the Baofeng. Repeater access is a little more involved than in ‘my day’ with a simple tone burst but the information is out there to get the job done.
The following links are a list of UK 144MHz and 432MHz repeaters, with details on how to set up your radio for access:
https://ukrepeater.net/repeaterlist.htm?filter=2M
https://ukrepeater.net/repeaterlist.htm?filter=70CM

You will often find most repeaters have someone who monitors it most of the time and is always willing to answer calls. As it’s FM and usually with squelch set you can have the radio monitoring in the background listening for people and respond to them. The range you can speak to people is the range of the repeater which is usually much further than you could do with a handheld on its own but limited to a local area, like Herfordshire for my local repeater for example.

SSB and CW.
These are mode often known as weak signal modes and where I like to do my operating. On HF you can speak literally all over the world and on VHF your range is vastly extended to 100s of km. 1000s with good conditions. This is usually because we use directional antennas to increase the range. This is a home made 9 element beam I made for 144MHz:
9 element 144MHz yagi beam
On HF though you can use bits of wire. This picture is an inverted V dipole made for 50MHz but I have made bigger versions for HF:
50MHz-inverted-Vee-close-up
This is a map of QSOs I have made, mostly on SSB or a derived data mode, some CW on mostly bits of wire. The map itself was generated by HRDlog, one of the sites mentioned above and from logged QSOs uploaded with Log4OM:
map of G1YBB QSOs

Contesting.
Contests are organised events with a given start time and end time and the object is basically to contact as many other hams as possible in the time. This is probably how I spend most of my on air time. I like the competitive element and enjoy improving my skill to do better. As HF is world wide there is usually a contest to be heard most weekends. On VHF and up there are also many contests through the year.
You don’t have to enter to take part, you can merely ‘give points away’ which is just answering the call of the stations who are hoping to win. Because contest stations want to do well they usually build high performing stations which means that a ‘normal’ station can be heard much further afield than normal so it can be a great way to make further QSOs. This is a common 144MHz style of contest setup:
G3YDD 144MHz contest stacksWith a big antenna system and great spot at the other end, you can be heard a long way off.
The RSGB run a lot of contests each year, here are the VHF and HF calendars respectively:
https://www.rsgbcc.org/cgi-bin/readcal.pl
https://www.rsgbcc.org/hf/
For most of the VHF contests you only need to know that all important 6 figure locator like IO82PA and usually give the other station a signal report and serial number. The serial number is just the number of stations you have spoken to in that contest so far. If you get interested in this look up your local club in the results lists to see if they are active. They would be glad to have you aboard!

Signals from Space.
This is something I have only done recently and I think it’s really cool. The ISS (International Space Station) often transmits SSTV (slow scan TV) images as it passes overhead and these can be received with your little Baofeng 144MHz FM handheld in the garden and decoded with your smart phone running an app (I use Robot36 on my Android phone) held by the speaker of the Baofeng. These are a couple of pictures I decoded that way:
ISS SSTV pic
ISS SSTV pic I find this really cool.
Lots of useful information here:
https://amsat-uk.org/beginners/iss-sstv/

Construction.
One of the great facets of this hobby for me is home construction. I prefer to let the Japanese make the radios, they are pretty good at it. But other things we can build ourselves. If I am not actually contesting, odds are I am building antennas for contesting. In the contest station above I built the tallest stack in the middle. A few of my projects are 9 element 2m yagi, 6m moxon, 20m moxon, 80m inverted V dipole, 20/30/40m link inverted V dipole.
There are many many plans for antennas on the web, literally any antenna you can think of.
This is a great low cost way to learn and experiment, and also get on more bands. Nothing beats the feeling of working new DX on an antenna you made!

SOTA and WAB.
SOTA (summits on the air) and WAB (Worked all Britain) are a couple of schemes that encourage people to be active on the bands. SOTA has activators and chasers. An activator takes his radio gear to a SOTA summit (hills and mountains) and makes QSOs with other people, chasers look for people on SOTA summits. Both can be rewarding and can introduce you to new places. Each activation gets you points and if you keep going can earn you an award.  Info here:
https://www.sota.org.uk/
WAB is similar but is based on collecting those WAB squares I mentioned earlier. Also trig points can be collected. More info here:
http://wab.intermip.net/default.php
There are also other schemes like HEMA which are similar to SOTA. Loads to look out for!

Data Modes.
This is a hot newish mode devised for extra weak signal communication. It is done by connecting your computer to the radio and the computer sends tones to the computer which at the other end can be decoded at really low signal levels. On one hand it has led to lots of people sat on the data frequency instead of getting on the SSB or CW sections and working DX but on the other hand it is very family friendly as you are not shouting into a mic or tapping away on a CW key. Also the DX possibilities are excellent.  The most often used program to do the data modes is WSJT-X found here:
https://physics.princeton.edu/pulsar/k1jt/wsjtx.html
WSJT-X main interface window
Looks complicated but once running it’s pretty easy to use. Plenty of how-tos on Youtube etc.
You can link it to your logging software to automatically log the QSOs. My setup is such that you make the QSO in WSJT-X. Once comepleted it prompts me to log it, which I do. It sends the QSO details straight to Lo4OM. Log4OM then (after a short delay to correct anything) automatically uploads the QSOs to the logging sites and often in a minute or so an email arrives to tell me the other station has confirmed! Awesome.
Here is an appalling quality video (two monitors wide compressed into small video size) of that happening in real time:

EME.
EME means Earth Moon Earth. basically you point your antenna at the moon, so does someone else and you use the moon as a reflector to bounce the signals to each other and get a QSO much further across the Earth than you could directly. Generally for this you need more power than the foundation licence so it is something that can make moving up through the licence levels worthwhile. It can be done with a good yagi for 144MHz (probably the busiest band maybe) and 100W if you have a big station the other end. The below image is an EME array built by RN6BN. Wow.
RN6BN 144MHz EME array

Chasing Awards.
Another thing people like to do is collect things that go towards awards. This can be DXCC (Countries) US States, Grid squares, IOTA (Islands On the Air) and so on. A benefit of the online logging sites and logging software as a lot of this can be done pretty much automatically. It relies on the other person confirming the QSO but other than that is pretty painless but can add an element of hunting for the next one.
For example, I just need Alaska to get my worked all States:
G1YBB Worked All States
But I have managed to get my first 100 DXCC:
G1YBB DXCC 100
On my qrz.com profile awards tab you can see all the awards I have gathered just from having QSOs and uploading them all:
G1YBB awards endorsementsAs you can see from the images these are attainable on a per band basis so there is always a new challenge to chase!

These are just a few tasters to share some of the avenues of radio that a newly licenced ham could find interesting.

Also check out the RSGB Beyond Exams page for other practical progression via the RSGB.

3D printers -The new sliced bread

It’s time that the saying about sliced bread was replaced with 3D printers. They are right up there with the internet in ‘how did we manage without it’ in my opinion. For the radio amateur they uses are never ending!

The yagi below is completely assembled with 3D printed parts. Not only that it’s mounted to a 30mm pole with 38mm U bolts using 3D printed reducers and the guy ring has an integral 3D printed plastic bearing.

19 element DK7ZB

Not only that the DK7ZB match coaxes were precision cut on a 3D printed cutting jig.
knife shown in jig

My HF inverted V dipoles and guys are wound up onto 3D printed spools and winders:
80m dipole pole guy winders

all guys ready to roll

I just built a 20m moxon made with loads of 3D printed parts:
kit of parts
Including a custom made for the job dipole centre with strain relief and tie wrap slots for the wires and the choke:
feed point choke
The things you can make are really only limited by your imagination.

Here is a time lapse video of a yagi dipole box being printed:

Ok sales pitch over, you know you NEED one, what now?

Well first choose your printer. I went for the Creality Ender 5 which is at the higher end of the budget printers. Loads to choose from though.
Creality Ender 5. 3D printers - the new sliced bread

To print anything first you need a design. This can often be downloaded from a site such as Thingiverse or you can design your own. To design your own you need 3D CAD software. Don’t panic, it’s not as bad as it sounds. There are many free options you can try like FreeCAD or TinkerCAD etc. I use Solidworks as I am lucky enough to use that for my job. Here is the box from the video in Solidworks:
dipole box 3D designOnce you have your design file you export it as an STL file (downloads from Thingiverse already are STL files).

The STL file then needs to be sliced for the printer to print. That is turning the finished shape into many thin layers, or slices, to make up the final part. Again, software for this can be free. A lot of people use Cura which is a free download.

Here is the box above in Cura ready for slicing. It all sounds complicated but once you have told Cura what printer you are using and what type of filament you have you can often print with the default settings very well.

Here is the 18th layer of printing that would make up this box:
dipole box 18th layer
Once you slice your design you save the output to a card or send it via USB and pass it to the printer and the magic begins.

There is loads of help and advice on the internet for 3D printing but it is a really useful tool for the amateur radio home builder.

Lightweight 20m moxon

Having recently received my new (2nd hand) short contest callsign I was keen to air it and with probably the biggest contest in the world, CQ WW SSB, coming up I decided I would try a single band entry and build a moxon that was as lightweight as possible to use after how well my 50MHz moxon performed for me. This page describes my lightweight 20m moxon build.

First step was the trusty Moxgen application and give it the wire size to get my start dimensions. As with the 50MHz moxon I then used 4NEC2 to recalculate the sizes for insulated wire as I was using.

4NEC2 settings for 20m moxon

20m moxon 4NEC2 sizes

This gave me this predicted radiation plot:

4NEC2 radiation pattern plots

And an expected SWR curve like this:

4NEC2 simulation SWR plot

Here is my NEC file for those wanting to work on their own version:
G1YBB_20m_Wire_Moxon.zip

Here are the calculated dimensions above applied to the 3D design described below. Note these dimensions apply to 16AWG/1.5mm2 tri rated wire. Other wire sizes with different insulation thicknesses will be different.
20m moxon dimensions

Once I had the dimensions I modelled up the wires in Solidworks to work out how long the spreader poles would be. This turned out to be about 4m so I ordered from eBay two types of 5m long fishing poles for evaluation. To do so I weighed a known length of the wire I was using to get an approximate weight each spreader would support and used something that weight to test how much sag there would be. The windjammer style pole had a thicker top section and was best.

Once chosen I could model up the poles themselves, weigh them and set their weight correctly in Solidworks.

To make the hub, rather than a thick metal plate and chunky U bolts and something to stop those U bolts crushing the poles I decided to use lightweight 1.5mm thick sheets of aluminium in a sandwich arrangement using 3D printed parts to grip the fishing poles without crushing them. I am a big believer in ferrite chokes at the feed point so I wanted a smaller support arm for that also. After my ultralight cobweb build which was unbalanced due to its 5th arm for the feedbox and choke I also wanted this antenna to be balanced, particularly as I intended to use this on the top section of my fibreglass push up mast which is 23mm in diameter.

20m moxon hub design

20m moxon 3D design

Solidworks is great because it will also tell you the centre of gravity of your design, which I used to find the best places to put the boom supports on my yagi designs. So I was able to see how lop sided the design was, which was quite a bit. A ferrite toroid with coax wound around it on the end of a pole is a fair imbalance. To counter this I moved the mounting point towards the feed point so the main weight could help counter it. There was still a lot of imbalance so I decided there would have to be a support for the reflector to help counter the feed arm and it would also keep the reflector in better shape in the wind. Still not enough and I didn’t want to increase the aluminium plate sizes. Hmm. So I made a wire guide for the reflector support (exactly like the ones for the spreaders) but used a relatively fat chunky M6 bolt and washers for the mass and that pretty much balanced it according to Solidworks.

20m moxon counter balance

The pink two way arrow shows the expected centre of gravity:

20m moxon CofG

One beauty of 3D printing is you can make exactly what you need so I could make pole clamps the exact size for the fishing poles and also arrange the poles compactly together (needed for the balancing) that you couldn’t do with something like Stauff clamps. I was also able to save on a bolt per side, every little helps. I started with the main pole clamps so I could test if my thin sheet sandwich would work as expected. As the holes were all in odd locations I decided I would mark out by printing a 1:1 scale print of the 3D model of the plate and taping it to one of the sheets and centre marking the holes ready for drilling. I then taped then G clamped the two plates together to drill the holes exactly in the same place on both plates. The holes in the plates are 4.0mm and so are the holes in the 3D printed parts. All the M4 bolts fitted perfectly.

ready to test for strength

I assembled the poles on and gave the assembly shake. All seemed OK.

I was able to press on with the design and printing. To mount the antenna to a 23mm fibreglass pole without crushing it I got some 32mm U bolts and printed some load spreading clamp halves. Also I was able to print some stiff but light supports to join the ends of dipole halves. Pretty much had a full kit of parts.

kit of parts

Final drilling could now take place.

drilling the smaller holes

drilling the mast holes

I did a test fit to the pole to ensure it fitted OK:

To connect the feeder I used a panel mount N type socket. I used RG316 to go to the feed point as it’s lighter than RG58,can handle more power being PTFE based and also being PTFE based can be soldered without it melting. I drew up and printed a plate for the feed point with holes to stress receive the dipole wires, slots for cable ties and clamping on the back to attach to the support arm.

feed point choke

Even though it’s “only” 14MHz I still like to keep the connections tidy.

dipole connections

The coax part done I can start final assembly. The N type socket had to be fitted first as it would be very awkward once built.

starting final assembly

Once mechanically assembled I took it out the front of house to have enough room to rig up the wires. I allowed an extra 20mm on each end to allow for tuning. Another good thing about a full 3D model is I was able to fit my 3D printed wire guides tot he spreaders using measurements taken off the 3D model and as seen below all was spot on.

20m moxon wires all fitted

I collapsed the poles to carry it round into the back garden to fit to the mast. Once all re-extended the first thing I wanted to do was check the balance by extending the 23mm section fully to see if it leaned over. Looks good!

seems to be nicely balanced

Pushing it up to about 30 feet to test I trimmed 10mm off each end to arrive at the below plot. Almost perfect match with the simulation.

20m moxon measured SWR

Time to test it on the air. Hmm. SWR with real RF way up in the red. It couldn’t be but was. I wondered if the choke wasn’t just not working but was working against me? It was meant to be 17 turns of RG58 so I hoped tightly packed RG316 would have same effect. I tried a GM3SEK choke my end in the shack, no good. Hmm. Talking with a couple of friends one suggested taking the N type off the plate.

feed point original plan

I couldn’t think this would have any affect but it was worth a try before I started cutting things.

working feed point mod

Well snag my blade! All was good now. The metal plate attached effectively to the braid of the coax certainly had some negative effect!

So now I had a working 20m moxon beam.

20m moxon ready for testing

As it turned out come CQ WW SSB weekend it was too windy for me to use the moxon, but I have had great success working USA on FT8 since. The below is where I was heard for a few hours with the moxon aimed for USA and working mostly USA and Canada.
G1YBB reception reports on 20m moxon
Final weight of the finished moxon was 3.2kg and it does compact down small enough to go on a roof rack, possibly even inside my estate though it could be a squeeze. I aimed for the SSB section of the band but it would have probably been to aim lower in the band to get a more usable SWR at the CW end. But performance wise I’m very happy with the new moxon.

Edit: October 2021
Since the initial build I have since soldered a little wire to the end of all 4 wire ends to move the resonance down to the digital end of the band. And since that I have made a 3 section wind up aluminium mast and can now use a rotator instead of running downstairs and up the step ladder!
But more interestingly, I re-measured the moxon at about 12.3m above ground on the new mast with LBC400 coax so very low loss at 14MHz and the whole band is below 1:1.6.    (I really must set the date on the analyser!)
20m moxon SWR plot

G1YBB Disguised ultralight Cobweb antenna

At my location it’s very difficult to have any sign of HF antennas (or any antennas for that matter) up in the garden. I’m already using a covertly erected dipole after dark using this quick erect fishing pole mount. But I was very interested in an ATU free multiband antenna. The hexbeam is nice but too big and needing a rotator. So I looked at the G3TPW Cobwebb antenna. For those unaware this is a 5 band dipole based antenna horizontally polarised and roughly omnidirectional working on 10, 12, 15, 17 and 20m. The folded dipole style with shorting points seemed more complicated than I fancied so I looked at the simpler G3TXQ cobweb design. This filled more boxes for me, single wires nice and easy to tune and a tidy looking feed box. However, it would still stand out in the garden due to it being some strange looking (to non hams) spoked wire thing. What I decided to try was up sweeping the spreaders to make my G1YBB Disguised ultralight Cobweb antenna look like a rotary washing line as there is already one in my garden. I was counting on the neighbours not noticing it had grown an extra arm and got a bit bigger. Except when actually in use I would keep it low down like a normal washing line such as this:
rotary washing line or G1YBB Disguised ultralight Cobweb antenna
I searched the internet to see what people had designed but no-one had done anything quite this style. I was sure it would work due to the success of the hexbeam, but to be sure I started a thread on qrz.com and got some advice from the man himself, Steve G3TXQ, confirming there should be no reason why it wouldn’t work. Thinking about it the wire positions on this design are quite similar to those on the successful hexbeam.

Looking at existing designs all seemed to be based on heavy aluminium plates and tubes to support the spreaders. My plan to use this on a fishing pole would preclude this sort of design. Mine would have to be ultralight to have any chance of working. The spreaders were easy, I would use the 2nd and 3rd sections from telescopic fishing poles like the ones I use for masts. These two sections are long enough (bearing mind the upswept angle means the spreaders need to be slightly longer than for a flat design) and are plenty stiff enough. At the bottom they are approx 20mm diameter tapering to 8mm at the tip. Five 4 metre poles were soon ordered from eBay at a cost of £37.70 with the delivery, making them just over £7.50 each. Here they are next to an 8m and the 10m fishing pole the finished cobweb will be used on:
5 poles for cobweb
Next problem was the centre piece which came to be known as the spider. I mentioned what I was looking to do with a non ham engineering friend and it turned out he was about to get a 3D printer on loan. A great answer to my problem, a custom designed 3D printed ABS spider would be perfect. I got straight onto to modelling up the antenna in a 3D design program. This would also allow me to be able to confirm the fishing poles would be long enough and see how it looked, find where the wires should be based on the wire lengths used by G3TXQ and also predict quite well the finished weight. After searching the web a lot for everything to do with the G3TXQ cobweb, many threads on qrz.com with posts from Steve himself, I designed it to have the feedbox in line with the 17m wire, making the 17m wire a square and all the others bunched into the feedbox.
Here is an animation showing how the antenna should look when finished:

And here is my original design of the spider:

I sent the CAD file over to my friend for 3D printing and the printer reported it would take 95 hours to print! So he decided to strip it down to just the 6 bores (five spokes and bore for the pole) and rebuild it from separate parts that would be glued together after printing. The glue should be stronger than the ABS he assured me.
My design was originally based on the main spider with a slightly tapered bore suitable for the 5th section down on my 10m pole. Not where I planned to use it, but hedging my bets until I got one working and mounted on the pole. I would then use one of 3 sleeves to move the antenna up a section per sleeve. During the redesign we were able to come up with a better idea using end caps and also save a bit of weight, all good.
This is the new design:

And on this page the printing process and spider assembly is detailed in more detail.

The spreaders slot into the spider bores and need to locate on a pip in the bores to stop any rotation (seen in the spider images above). This is mostly for the feed box to keep it in position but also to securely locate all the spreaders. The ends of the fishing poles are not cut square so I marked a line to indicate the longest part and marked out for the slot to be made with a Dremmel 3000 and a small milling like bit:
spreader marked out
To Dremmel the fibreglass safely I set up the hoover as a dust extractor which was very effective:
hoover setup for fibreglass
Finished notch, which is done to all 4 spreaders and the feed box spoke:
spreader notched
So I knew the notch was deep enough I marked the spreader fitted before the notch is made, then added another mark 3mm up the pole (depth of the pip):
spreader before notching
Spreader fitted after notching:
spreader after notching

Once this stage was finished I extended each spreader and feed spoke in turn and marked the smaller section at the end of the larger section to indicate how far it fitted, then took them back apart and applied some varnish to the part of the smaller section that makes the joint and extended them again adding a little extra force to ensure they are jammed nicely and hopefully the varnish should ‘glue’ them together. I then added some varnish to the outside of the joint to seal against water running down the joint and inside the spoke pooling in the ferrule. You can see in the picture below that the spreader on the left is going to need another application or two of varnish to seal that gap:
spreaders varnished

The feed box fits on the feed spoke suspended underneath the feed spoke pole. The angle of the feed spoke bore on the spider is slightly steeper to align the wire entry of the 17m straight in, one nice advantage of 3D CAD design.

The feed box is an ABS box from Farnell, their part number 244-4686, manufacturers part number TW7-5-11B. Note that Farnell do free delivery to non company accounts now. This size was chosen to be the smallest usable and (hopefully!) fit the feed balun inside:
Feeb box
The buses for the wires I wanted also to be lightweight but not compromise on the amount of copper so I abandoned my plan A of some copper clad FR4 when I found some 0.32mm copper sheet. Perfect. That equates to 10 ounce copper where the FR4 copper would have only been about 1 ounce and I have no dead weight in FR4:

As copper sheet is pesky to solder to I wanted to tin one side before trying to solder even more copper to it in the form of the balun and wires. First attempt with a heavy iron and a hot plate was not very successful. The solder looks awful and you can see the copper discolouration on the bare part before we gave up:

A plan B was required! A multi zone reflow oven and some solder paste was much more successful! Not something everyone has access to but I do so I may as well take advantage of it. The scratches are from scraping off the flux:

To mount the copper flat to the base of the box to maximise space for the balun and simplify the build I needed to Dremmel off the four PCB moulded mounts. For good measure I removed the same mounts from the lid. No point carrying dead weight even if small!

As I like things neat and tidy, I have taped the two copper bus plates back to back to drill a small pair of mounting holes through both together so they match:
copper plates for drilling
Here are the two bus bars fitted with M2x6mm screws:
bus plates fitted to box

Instead of nuts and bolts to join the wires on I wanted to minimise weight again so just soldered directly to the copper. Not so good to replace wires but I like to bridge cross problems if and when it’s needed. As I didn’t want to waste space in the box and add extra weight there are no spacers for mounting the copper bus bars. They will sit flat on the bottom of the box. But as I will be soldering with it in situ, especially for the fiddly to fit Guanella current balun, I have added some Kapton tape to the box to hopefully protect it from the heat a little.

The wire I used is 16/0.2mm stranded which measured to be pretty much the same as G3TXQ describes in his text though in his photos the coloured wire looks a little chunkier to me. For the actual lengths I started with the lengths given by G3TXQ here:
wire lengths
I then referred to his wire thickness adjustments for hex beam wires here:
wire size adjustmentsto see how much things changed for wire diameters then decided that an extra 3 inches each should hopefully be more than enough. I also took note of some predicted and measured figures for the amount the resonant frequency changes when trimming provided by Jacek SP3L in the disguised cobweb thread higher up the page:
trim length predictionsChanging the wires with my construction would be a nightmare so hoped this extra length would be plenty.

Where the wires exit the feed box I’d planned to use Hellerman H20 rubber sleeving but it was too loose a fit to the wire, so instead I used adhesive lined heatshrink which would also prevent water ingress between sleeve and wire.

To solder the wires to the copper bus plates I removed them from the box and placed them onto a piece of MDF to prevent heat sinking away. Before doing so I drew around the box and marked the wire entry points so I would be soldering the wire in the right places. The pre-cut to length wires were then threaded into the box treble checking the order before soldering:
ready to solder wires
Using a 100 watt Weller mains power soldering iron with a 6mm chisel tip I was easily able to solder the wires on with sound looking joints and without melting the previously soldered joints:
wires soldered to bus
Once cool I fed the wires back into the box and fitted the plate and repeated for the other side:
ready for balun

I’m using an N-type socket for the feed input connector as I much prefer them over the SO-239 and PL-259 UHF connectors.

Having created the design in 3D CAD I was able to use my model to tell me how long to cut down the fishing pole for the feed box arm. Using the end of the centre spider tubes as an ideal reference point for a tape measure told me the spot to mark for cutting, in [inches] and mm:

As things worked out the position for the feed box happened to span the joint of the telescopic pole. I had originally planned to use saddle clamps to attach the feed box to the pole, using the same screws for those to hold the bus plates in but I needed two sizes neither of which I could find and to save making them I just bolted the box to the pole with 2x M3 screws and nylocs. I used nylocs so I could tighten up without crushing the fibreglass pole but not have the nuts work loose.

Once the box was fitted to the pole I could then fit the balun. I wanted to fit the feed box to pole first in case once the balun was fitted it was blocking the access to the screws (quite likely). To try and reduce the damage to the edge of the box during soldering (the iron ALWAYS finds a way of melting the box when you are working inside no matter how carefully) I cut up a Pepsi can (other canned drinks are acceptable!) and folded it around the edges, hoping it would make a good heat shield:
ready for balun soldering
For the feed balun I used the exact same  FT 140-61 ferrite toroids as G3TXQ and RD316 (which is just RG316 with a double screen)

4 lengths of RD316 taped out for marking exactly the same lengths. Apparently the outer jacket of RD316 is repellent to all marker pens including biro, Steadler permanent markers and sharpies. So I marked the line to strip the braid off with masking tape then slit down between each piece to leave a strip on a marker:
making the balun 1
Outer jacket removed and bits of heatshrink added to keep the 2 coaxes together. This also helps stop the coax curling up all the time:
balun 2
Close up showing quite closely matching outer jacket length remaining:
balun 3
Both 1:1 chokes wound:

To fit the balun into the feed box I first loosened the four screw holding the two bus plates in so I could slip some thin card (from a cereal bar packet) under the ends of the bus plate where I would solder the coax (paralleled end) then soldered the coax to each plate. Then I removed the card and tightened the screws back up on the bus plates and added a drop of varnish to each one. I then fitted the other end (the series part of the balun). This job didn’t turn out to be as much of a stressful procedure as I expected. The heat shields worked perfectly and the box survived without any damage! I used some Hellerman rubber sleeves where the wires exited the feed box

balun fitted in feed box

As this project has taken me so long because I started make VHF & UHF yagis for contesting and doing lots of contesting, in that period I have moved away from using the fishing pole as I now have a more heavy duty pole this can go on. I did test mount it on the fishing pole and it is still viable. But it fits even better onto my 23mm diameter 3mm wall mast top section. To do this I designed and 3D printed adapter washers and simple locking collars to fit top and bottom. In the first photo you can see that without my glasses on I have fitted the collar upside down as the ridge is supposed to mate with the groove.
upper spider support collar
lower spider support collar

The wires are fitted to the spreaders with some 3D printed guides I drew up and printed. The wires pass through holes so the spreaders should self centre and tension be equalised all along the wire.

3D printed wire guides

As my design is closely following the build of Steve G3TXQ I was able to use 3D CAD to determine where the wires should be attached to my spreaders if all goes to plan and at the very least give me a good start point. This could of course change if my wire turns out to be thinner or have a different velocity factor from the wire Steve used. These are the positions using the same wire lengths as on Steve’s page:

To join the ends of the dipole I used nylon cord as used on bathroom light pulls only a bit thinner, thin, strong and light. I used a tight fisherman’s knot in the cord to grip the wire and taped the string to the wire ends to keep the wires straight at the ends whilst tuning then locked off once tuned with a cable tie as well.

wire to string detail

Tuning I did with the extremely useful MetroPWR FX700 antenna analyser, taking notes of how much I cut off each time affected the resonant frequency. I decided my target tune frequencies would be somewhere near midway between the SSB and data portions as from home data modes is very family friendly with no shouting to annoy anyone.

Cutting and tuning results

MetroPWR FX700 antenna analyser

SWR results are as follows, measured at about 30 feet above ground.

cobweb SWR on 20m band
cobweb SWR on 17m band
cobweb SWR on 15m band
cobweb SWR on 12m band
cobweb SWR on 10m band
cobweb SWR on all bands

Finished antenna pretending to be a washing line. It sure looks like one but I don’t think I quite have the disguise cracked…

disguised cobweb on mast

cobweb looking up mast

As this started off to be an ultralight cobweb it’s worth stating the weight. Weighing myself alone and with the cobweb complete on the bathroom scales it comes out as 1.2kg overall.

Final Note:
It is with sadness that this took me so long to complete, and during that time Steve G3TXQ succumbed to illness and is now SK. Steve had some thoughts on the antenna that we exchanged, both via email and in this QRZ thread. It’s a great shame for me he never got to see the finished antenna he inspired. However the QRZ thread did stimulate some good experimentation on cobwebs and is well worth a read through for that alone.

 

RSGB 50MHz Trophy contest June 2020

Earlier this week I built a simple wire moxon antenna for 50MHz for use at home, detailed on this page (link). The impetus for this build was to contribute towards the Hereford ARS campaign to retain the RSGB VHF Championship Trophy that we won over the year long 2019 contesting calendar.
finished moxon up for testing

I already have a 50MHz yagi (link) for use portable when contesting but at 7.2m long it’s just too large to assemble in the garden and if I could get it to the height required for a clear view would put the fear of (deity) into the whole estate! So the plan is to add a few club points using the little moxon.
50MHz 6 element DK7ZB yagi
As you can see a vast difference in antennas! However I was not completely dismayed. I have been out contesting on the hills often with the big yagi and really struggled to break pileups to DX on sporadic E openings, usually with many other club members who I usually do better than just calling over the top of me. I’m always low power at 10W, but look at that beam man! So I have come to the conclusion that the vertical pattern of the long yagi is just not suited to the angle required to get good results on Es. I may be wrong as many others use reasonable beams but my post summer 50MHz contest catchphrase is:
“I bloody hate Es season!”

But the radiation plots of the moxon design I thought were very promising. Not only a great big fat front azimuth lobe (in red on graph below) with a 3dB beam width of 78° but a huge vertical shape )in blue on the graph) to it covering all take off angles you could imagine for Es. So despite having way under half the gain of ‘the beast’ that disparity in gain once we get off the main heading the moxon would ‘catch up’ a little and should also be launching skywards when required. My theory anyway!
Moxon hor and vert radiation plots
So, contest day. I planned to do just 6 hours and as it’s more family friendly to get that over with in one session for me so I opted for Sunday morning and the last 6 hours before the contest ended. Amazingly for me I seemed to have pretty much cherry picked the best slot of the 24 hours. I was 4 hours into the contest before I got any other G squares than my own and IO81 adjacent to my square (I sit on the join line at IO82PA). But I was busy with the Es! Great fun. I only have 100W max on 6m and whilst some of the pile-ups especially to EA were hard to break it was very enjoyable! One station ( I think Italian) even commented “wow such a huge signal” after our QSO. This is on two bits of wire and some plumbing tube!

I was completely unable to raise all the ‘local’ EU countries like F, ON, PA nor could I get any GD, GI, EI, GU, GJ. If I had their country and square mults would have upped my score nicely. However my new temporary summer 50MHz contest catchphrase is:
“I bloody love Es season!”

QSO map below:
G1YBB 50MHz Trophy 2020 QSO map

Easy building of a moxon antenna with 4NEC2

As we are still on lockdown and my 50MHz yagi is literally too huge to fit in the garden let alone erect on my lockdown lash-up system I decided I needed to make something smaller to use at home. I didn’t have any aluminium tubing at home long enough to make a small yagi so I decided to make a moxon antenna on the recommendation of a friend. These are very compact and easy to make so it seemed like a plan. I decided on a wire based version as although I have some 12mm tube I could cobble together I didn’t have anything I could get today for the corners. Wire it is. I decided easy building of a moxon antenna with 4NEC2 simulations to find the correct starting point would be a cool project.

I’d already looked around the web and compared the various online moxon calculators and the AC6LA Moxgen program (link) and the Moxgen program seemed to be the best fit for the suggested spreader angles. (Even though I’m not using spreaders as such.) It’s dead easy, just put your desired frequency in and the wire size and click calculate:
Moxgen calculated values for 16AWG wire
That’s it, job done. Almost…

I’m using normal insulated wire but the calculator doesn’t cater for the change in velocity factor from insulated wire. So I decided to run it through the free 4NEC2 simulation software (link) to make the required adjustments to the dimensions so it would work with minimal fiddling after. I love building, hate fiddling. Now, before you start backing away from the PC this is quite easy to use and just needs some really simple maths to do this. Stick with me. Look at the image above and see I have selected Format NEC on the right. You just do that and click the Generate Model button and save a file ready to open in 4NEC2. Run 4NEC2 and click Open and load the file you just made.
4nec2 main screen
Click that green calculator looking icon to bring up the next screen, choose frequency sweep and check the start and end frequencies are a useful range and that the step size is not too large, then click generate:

We then get a plot showing us the expected SWR curve of the antenna:
SWR of Moxgen design as supplied
Oddly minimum SWR at 50.1MHz rather than 50.2MHz but looking good. We can click the green calculator button again and this time plot the azimuth plot we are interested in:
generate 4NEC2 far field pattern
Which results in this plot:
Gain of Moxgen design as supplied
We can see the moxon should have about 6dBi gain and the amazing front to back ratio it is known for. Next to nothing off the back.

This is all very well but I’m not make it with bare wire so my antenna will not look like this without some tuning. First of all we need to add in the insulation so we can see what the effect will be. On the main screen, to the left of the green calculator is a red book, for editing the information that defines the wires making up the simulated moxon. Select the Source/Load tab, and tick Show loads. We then add two lines selecting as shown below from the offered selections. For Tag, First & Last we put 0 (zero) which will apply the setting to all parts of all wires. My tri-rated wire has insulation 3mm in diameter so I enter the radius, adding the mm to ensure correct scaling is used:
parameters for coated wire added
Once done we can click the green calculator on that screen, select frequency sweep again, but widen the scale. I’ve gone 5MHz either side of 50MHz. You can see the resonant frequency has moved 2.5MHz due to the effect of the insulation’s velocity factor:
frequency shift with insulated wire
So if we had built to the Moxgen dimensions using my insulated wire we’d be looking at an SWR of about 2.2:1. So we need to make some simple adjustments. The dimensions of the wires are on the Geometry tab below. Looks complicated but it’s just a few repeated co-ordinates. Some with a minus ( – ) sign to make the equal around the center of the axis to plot correctly:
original design geometry
What we are going to do is put those numbers into symbols, or what we would call variables in programming. When you look above there is only actually 4 different numbers used so it’s not complex. You can give them any name you like, even Harold but I have gone similar to the Moxgen image further up. Just click the Symbols tab and enter as shown below. You’ll see a 5th value called Vf. I’ve already tuned it by now but pretend I haven’t:
values changed to symbols
Now we need to flip back to the Geometry tab and put the letters (W, E, DirS, RefS) where the numbers used to be:
geometry changed to symbols
If you were to run the SWR plot again now, it should be exactly the same, best SWR on 47.5MHz. But finally we add in the velocity factor. To the end of each of the letter symbols add without spaces
*Vf    (star V f):
velocity factor applied to design
Now we can run the SWR plot and it will apply a Vf correction to every dimension. I found 0.945 by trial and error. They say Vf for wire is between 0.95 and 0.98. I knew mine would be the lower end as it is quite thick. Now if we run the SWR plot, changing back to the 49 to 51MHz range we get this plot:
velocity factor corrected SWR plot
Back in business. A point to note here. I’m aiming for the SSB section of the band, but if I wanted to cover more of the band I would still aim at the lower frequency with this design. You can see the SWR curves rises steeply on the LF side but gently on the HF side. Anyway, if we run the far field plot we now get this:
velocity factor corrected gain plot
As you can see this has changed. A bit less forward gain because we are chucking some out the back now. Now as I mostly do contesting this doesn’t bother me at all but it is interesting nonetheless.

So now we have redesigned the original dimensions to my real world application of actual wire, we should be shooting for success. We just need to apply the scaling factor of 0.945 to the original sizes with a calculator and a little rounding to sensible numbers:
Moxgen adjusted values for 16AWG wire
So for the reflector we need a wire 2051+384.5+384.5 – 2820mm long and for the driven element 2 wires 1025.5+305.5 = 1330.5mm long.

Now we can build the antenna and have a good chance of it working!

I decided to make it from a small length of 20mm boom left over from VHF yagis and find some plastic pipes from the DIY shop to support the wires in the A dimension and just stretch them between the pipes for the E direction:
material costs receipt
I bought a terminal block strip with the intention of using the brass inserts with nylon rope to join the ends at the C direction but didn’t after so total cost of parts not lying around £3.87. I used my red yagi elemt plates to mount the pipe clips and snapped the pipes into them after cutting to size. They didn’t really grip the pipes so I just taped them on to stop them sliding sideways.
I fitted a short tail of RG223 to an N-type plug, split the other end into braid and core and soldered the two halves of the driven element on and threaded those into a hole drilled in the centre of one pipe. After testing I sealed this with liquid insulation tape:
driven element entry detail
I had a better idea for the ends of the elements at dimension C. I quickly modeled up a small plastic part like so and sent two to the 3D printer:
wire ends connecting strip 3DThe holes are a snug fit, tight enough to hole the wire until final testing. I marked lines on with a Sharpie 60mm apart and fitted the wires. Once tested I locked off with cable ties:
wire end connecting strip
So, the acid test. What does it measure like?
SWR as designed
SWR plot is very close but shifted down in frequency. This is because of the plastic pipes which I can’t (or don’t know how to) model in 4NEC2. Not a problem as I expected this and knew that now the wires would be ‘too long’. So I cut 10mm off the end of each element half (4 ends) and ended up with this:
SWR plot with 10mm trimmed off(just noticed my analyser clock is way out LOL)

Pretty much an exact match to the simulation with 30 seconds of trimming. Just how I like it!

The finished antenna looks like so. It actually looks better than this because this is before cutting the 10mm off each wire end.:
finished moxon up for testing

Lockdown lash-up mast base

The coronavirus outbreak of 2020 put a stop to all portable radio activities so like many people I was forced to adapt and overcome and set up something at home. For non rotating mast systems I strapped a mast to the YL’s parasol base:
old umbrella stand base
This worked for smaller dipoles but I wanted something a bit sturdier and the YL wanted her umbrella back! So I decided to make a new one. I thought about making something from scratch but after asking the local club members for ideas it was suggested to use a tamper that builders would bash sand down before laying slabs or bricks. A quick Google located one in stock in the local Toolstation:
roughneck tamperThis is a cast iron 10″ base and a fibreglass handle. Cost me about £35 which is cheaper than some of the suitable umbrella bases I was looking at. I click and collected it. It didn’t seem that heavy at all to be honest but I’d already planned to fit it to a paving slab so wasn’t an issue. A quick session with the drills and the tamper was securely fixed to one of those heavy council style paving slabs:
new mast base fitted to slab
The fibreglass handle feels pretty strong with some give but also felt like it would snap before that slab budged! This would normally only be used as the support until guys are attached anyway.

Before fetching the tamper I liked this design as the 4 webs I thought would be good for locating the bottom of the pole for lashing with a bungee. But in the end I decided to design and 3D print a locating guide that would stop the pole from twisting in relation to the yellow handle. Quick bit of CAD:
mast guide 3D modelThe hole on the side is to clip the first end of the karabiner bungee into while I lash it tight. Once a few turns of bungee are overlaid there is little stress on the plastic but it feels pretty strong anyway. This I printed in PLA which is easy to work with though ABS or polycarbonate would probably be better. There’s not a lot of stress on these parts so should be fine.

The biggest problem I had fitting these was getting the rubber handle off! it’s only glued on at the domed top but pesky to remove. Got there in the end and fitted the guides. they were a beautiful fit, close sliding fit. So close in fact the label halfway down stopped the slide  so I had to open it up a bit. Couple of small M3 stainless screws and nylocs and job done. Two bungees and we’re ready to rock and roll:
base with mast fitted
Close up of the top guide:
pole guide and bungee
All fitted a treat.

You may be thinking all well and good if you have a 3D printer of course. You could do the same with bits of wood I’m sure but I do heartily recommend a 3D printer. They are amazingly useful and very affordable now, although the filament at the moment is doubled in price due to the high demand when the 3D printing community was mass producing PPE equipment for the NHS.

70cms RG179 & RG302 DK7ZB match cutting jig

This DK7ZB match cutting jig will enable you to cut RG179 75ohm PTFE coax accurately and repeatably to the length required to make DK7ZB 28ohm matches. RG179 is chosen as it is easy to work with and is best used for antennas that will only be used as part of an array, or lower power use only. It should be good for about 300W PEP on 432MHz. This jig arrangement gives you enough braid to solder to with a very short length of exposed PTFE dielectric. At 432MHz you want to be keeping your ‘tails’ short and tidy for best results.

Design goal:
3D stripped cable
Reality:
RG179 one end prepared

Building the jig.

You need to print the following from the files supplied:

1x           Part1
1x           Part2
1x           Part3
2x           Part4
2x           Part5

I used PLA at 0.1mm layer height and printed them in the orientation that they are used:
3D printing layout
Download the RG179 STL 3D print files

I fitted them to a metal plate so I could clamp them to my bench. Holes for M3 bolts are included in all pieces. Small wood screws could be used to screw to a board.
jig and tools

To set the overall length (finished braid and cut for 2nd end) I used 2 pieces of tube the  closest size to fit RG179 inside I could find which I found in a model shop and is brass tube 4mm diameter x 0.45mm wall thickness. Code BT4 M by Albion Alloys.

One needs to be cut to 120mm (¼wave for RG179) and one to 132mm. The 120mm is a critical dimension. The 132mm wants to be pretty close. Varying by a small amount is not game over but it means the stripping lengths may not be 100% symmetrical so worth looking out for this.
Edit: I have since re-calculated the length for RG179 and other 75ohm PTFE cables and found that it comes up with 121.4mm. I used this to make a 19 element yagi and the match was spot on (bottom of this page).

These tubes need fitting into Part4 & Part5. I ran a 4mm drill through both parts to clear the prints for the tube, and a 1.6mm drill through Part4 only for the coax. This hole needs to take the PFTE dielectric with a nice close fit but not too tight. Dielectric should be 1.55mm so 1.6mm drill should be about right.
NOTE: when running a 4mm drill through Part4 (if required) only drill 7mm deep to clear the blue highlight below. The bore opens up inside after 7mm to ensure there is a flat surface for the brass tube to sit against internally:
Part4 showing internal to drill

Part4, Part5 and the brass tubes then make assemblies like below. I used Loctite 243 sparingly on the tube before ensuring it was pushed completely home into Part4 then on Part5 when that was fitted. Part 5 is just a support and needs to be about 10mm from the tube end.
120mm tube assembly

Using the jig.

Part1, Part2 & Part3 are designed to be used with a craft knife with the type of blade where you can break sections off, like this one:
stanley craft knife

Extend the blade far enough to easily span the two guide slots. Only light pressure with a sharp blade is required. Do not ‘saw’ with the knife, instead rotate the coax. Start with a length of coax about 150mm long.
DK7ZB match cutting jig with knife shown in jig

Step 1 – strip the outer jacket.

Insert one end of the coax into Part1 until it hits the blind end, insert the knife and rotate the coax. I found the jig worked perfectly as printed, but in case near each guide slot for the blade is a hole that will take an M3 grub screw to fine tune the blade height. This cut is the tightest tolerance one.
Part1 for cutting jacket

The outer jacket should be scored not fully cut through. This is to ensure no braid strands are cut. Gently flexing the coax should snap the jacket easily without damage to the coax.

DO NOT FULLY REMOVE THIS PIECE YET.

Carefully slide the jacket towards the end to reveal about 10-12mm of braid:
jacket moved to solder braidNow lightly tin the braid with solder. Enough to wet all the strands all the way round but not too much to increase diameter. I find ‘real’ solder with a lead/tin mixture better than the lead free stuff. Once done the jacket piece can be removed fully. Lightly tin the rest of the braid:
braid fully tinned

Step 2 – cut the braid to length
cutting the braid

Insert the braid into Part2 until jacket stops and again fit knife and rotate the coax at least once full turn.

Again this will only score the braid, in order to ensure the PTFE is not damaged.

Also again, gently flexing the braid at the score mark should fracture the soldered braid cleanly at the score mark. Braid can now be removed easily.
braid stripped

Step 3 – cut the dielectric to length

Insert the coax into part 3 until the braid stops on the inner stop:
cutting the PTFE dielectric

As before, fit knife, rotate coax at least one full turn. The PTFE inner will be scored but should easily twist off, shearing at the score line neatly. Lightly tin the stranded inner conductor.

Your coax should now look like this:
RG179 one end prepared

Step 5 – trim overall length

Insert the stripped end of the coax carefully into the 132mm tube assembly, rotating it as you go to ensure the PTFE dielectric enters its hole and the braid sits up against the inner stop:
cutting 2nd end coax

Using flush cut wire cutters cut the coax nicely flush with the brass tube. The neater the better, this will determine the position of the 2nd jacket strip. You may want to grip the coax with the cutters using the brass tube as a guide then carefully pull out the coax from the tube as you cut it so there is some to grab hold of.
2nd end coax cut

Step 6 – strip 2nd end jacket

Repeat Step 1 above so you have this:
2nd end jacket stripped

Step 7 – cut 2nd end braid

Slide fully stripped end into the 120mm brass tube rotating it as you go to ensure the PTFE dielectric enters its hole and the braid sits up against the inner stop:
cutting critical braid length

Hold your sharp knife blade on an angle to match the blade’s cutting edge ground angle so the cutting edge is flush with the end of the brass tube and using gentle pressure rotate the coax by twisting the bare braid on the left letting the blade edge roll along the circumference of the braid. You are aiming to score it as in Step 2. Remove from the tube and gently snap the braid at the score line and remove as in Step 2. You should now have a braid length of exactly 120mm:
braid cut to 120mm

Step 8 – cut the dielectric to length

Repeat step 3.

You should now have a finished cable:
finished quarter wave RG179 cable

You can now repeat this process as many times as required and should get extremely similar pieces.
I always ensure I cut my matching segments for all antennas I might use together from the same reel of coax in case of any manufacturing differences.

To make the actual DK7ZB match I like to pair the cables with short lengths of adhesive lined heatshrink. One of the few things that tames that slippery FEP jacket. The pics below show how I connected up the short tails.

Match-N-type end
Match-dipole end

RG302 Version.
Since making the RG179 matches I have built a version using RG302 for better power handling.
Principal is exactly the same as above except I used 8mm aluminium tube (spare element tube) with 1mm wall thickness.

This is the result I got:
19 ele DK7ZB N-type box19 ele DK7ZB dipole box19 el DK7ZB SWR plot

Download the RG302 STL 3D print files

Icom IC-9700 Contesting review

This is my brief Icom IC-9700 Contesting review based on my experiences in many RSGB and other contests, nearly all portable on a hill top and all three bands the IC-9700 covers.

Icom IC-9700

I bought the Icom IC-9700 at the time the second batch of this radio to hit the UK were being hotly sought after. I had recently got the IC-7300 before it, which I also love, so I was pretty keen to get this one to add to my portable contesting stable. In it’s early days there was a LOT of negative talk about dynamic range and frequency drift, I’ll touch on that at the end.

I can honestly say right now, I love this radio! Review done.

Oh you want to know why? OK headline points for me…

Functionality.
The IC-9700 has brilliant functionality for VHF contesting. The spectrum display is the biggest new thing to me (on 144MHz and up). Whilst this is brilliant for spotting signals on the band (and for this reason I think everyone ELSE should have one to find me!) not only that it has made the biggest gain to my 144MHz performance since getting the 9700. The way it actually did this, apart from the signal spotting ability, is to highlight why I was getting so much QRM on 144MHz. I always blamed other club members out portable nearby, line of sight, and some using FT-991 radios. Whilst they did batter me there were some nights I couldn’t find who it was killing me on the old school radio I was using. The 9700 soon showed me:
9700 bandscope showing pager QRMI was getting awful QRM and the OVF warning in regular all night long pulses, as you can see all over the band, but particularly hammering me where I usually run (144.265). That’s no ham! We determined the source to be a local (100 metres away) pager system. For so long I had suffered this QRM without realising the true source. It took me a while but after buying one filter that wasn’t sharp enough I borrowed another bandpass filter that took out this pager QRM and left me with a bandscope a little healthier looking!
9700 with pager QRM filtered outCouple this with the excellent receiver the 9700 has and it has truly transformed my 144MHz operating, and also on the other bands based on the receiver.

In the first QRM image above you can see I have the inbuilt memory buttons showing. The IC-9700 has these for voice and CW (maybe data?) and these are a complete godsend. I use two for contesting and one for general calls pre-contest. They auto repeat and you can get an external box to replicate the first 4 buttons. (Another build in the future)

You can connect the 9700 to your PC with a simple USB cable and get CAT control and data in out for things like digital modes, computer reading and sending of CW etc. So much easier than buying a rig interface box. I just use CAT when I am contesting.

The 9700 will also record both sides of a QSO as you go onto the SD card. Useful for DXers and the RSGB recommend doing this for contests. I guess it would be good for resolving disputes.

Those are probably the biggest plus points for me that I use all the time. Receiver functionality like adjustable filters and notch filters etc are there but not unique to this radio of course.

Performance.
As I touched on above, the radio performs excellently in my opinion. It won’t match a top HF rig into a high spec transverter of course, and may not have the optional roofing filters some radios have, but I have done very well with mine and I have seen quite an improvement in my scores since getting this and the 7300 (which I also love and has basically the same features). I find the receiver excellent and pretty good at withstanding some strong QRM locally as we have a pretty good turnout in the UKACs at Hereford ARS.

This radio does satellites (I know nothing about that) and can receive on two bands, but one of the first things I did when I got it out of the box was turn off the sub-receiver never to be used since. Until this March! March sees the RSGB March 144/432MHz where you need to operate on both bands at the same time. Not possible simultaneously as a single op but I set up with two antennas and two amps and ran on 144MHz and 432MHz, using CAT control from Minos to change bands by changing logs. Worked so well. However one thing I didn’t realise it could do was receive on one band while transmitting on the other. In the video below the 9700 is sat on top of the 70cms amp that you hear click when I Tx

I’m pretty impressed by that (as you can tell).

The “Bad Things”
When the IC-9700 was first announced there was a lot of talk about insufficient dynamic range to handle huge signals whilst receiving weak ones. Now whilst this might show up in a contest like 144MHz Trophy (IARU Region 1 in rest of EU) with huge signals from multiple antenna arrays and QRO amps (in fact our club station had such a complaint from a fairly close line of sight 9700 user) I can say that I have never had this that I can recall from another radio amateur. The only time my 9700 has shown OVF (overflow) is from the local pager mentioned above and from the Clee Hill radar station on 1296MHz. Bear in mind that I operate 11km away from G4ASR who has been known for being a very strong signal for many, many, many decades. (hehe Dave). I get strong signal QRM from him if too close in frequency when pointed at each other, but he has never put the 9700 into OVF (That is NOT a challenge Dave)

When the first units were received there was a lot of talk about temperature based frequency drift. It was the end of the world as we know it. Icom has since come up with a firmware upgrade to assist and GPS locked board and mods are available. I feel it’s worth mentioning I am using one of the very early units and it is as it came out of the box. No firmware updates have been applied. None have had anything I felt I needed. I don’t do data modes (to date) just primarily SSB. I have never had anything mentioned to me about drifting and never noticed anything on receive. That’s on all 3 bands. I do only normally use the radio on 10W on each band so I probably generate less of a temperature change. (They say it multiplies up on 1296MHz)
So if you want to actually talk to people yourself rather than letting a computer do it for you, the 9700 works. Works well.

One real issue that has reared its head with me is the single PTT output for driving amps and transverters etc. There is only one contact available that grounds on Tx for all three bands. People have designed units that read the C-IV data and generate a band specific PTT output and I do plan to build one of these myself. For a recent dual band contest however I did something a little more old school:
9700 PTT switch front view9700 PTT switch rear view9700 PTT switch side view
Summary.
I am really happy with the purchase of the IC-9700 to accompany the also great IC-7300. One thing I like is the matching form factor. They are practically identical so I can alternate them in my portable box depending on the band I’m using.
G1YBB portable contest box

My suggestion is to think carefully about what the naysayers are actually saying and decide if their nays will actually have anything to do with what you want to do with the radio. For example, I’m not currently interested in EME or data modes like FT8 so the drift ‘problem’ doesn’t bother me. If I decide to do data, then there are firmware and hardware solutions ready to solve that.

Did I mention I love my Icom IC-9700?