Accurately cutting yagi elements to size

I planned to build more 144MHz & 432MHz DK7ZB yagis for contesting to use in arrays so I wanted to ensure I could make them accurately and repeatedly and also without taking forever doing it! Thus I needed to come up with an efficient cutting jig.

I would use some threaded bar to adjust and set the length and steel angle for the supporting the aluminium tube and cutting the length. First I calculated the range of length between the longest reflector and the shortest director then a quick knock up in Solidworks gave me the length of stud required and ideal places to weld the angle to do the cutting. The studding is M12 because a nut for M12 will take a 10mm ali tube with a little clearance. The long M12 barrel nut (Screwfix, few pence) is locktighted in place. From the left the angle brackets have the following holes: 12.5, M12 tapped, 10.5, 10.5, 10.5:
144MHz element cutting jig

Some cutting, drilling and tapping later and I have this (the observant will note it’s not exactly the same as the intended design-more on that accidental stroke of luck later!):
cutting jig completed
Usage is very straightforward. First I G-clamp it to the bench then I used one piece of spare element tube as the setting piece, doing all elements in sequence, longest to shortest. So I set the jig and adjust, cutting and filing the setting piece until spot on then do all elements that length then onto the next element size using the same setting piece. Simple, but more importantly, very accurate and repeatable. I did try calculating the distance a fraction of a turn would give based on the thread pitch but with a simple tapped hole the thread backlash made it too unpredictable so found it easier to measure the amount the cutting piece protruded when setting for the next size down with the small vernier in the photos above and start from that point and fine tune on the thread and lock nuts.

To actually cut the elements (after using the jig to prepare one end of all elements to ensure it was nice and square and deburred) I just slide it through the 10.5 clearance holes into the long nut and hold it pressed against the long nut with one hand. With the hacksaw tilted slightly to start a cut just away from the steel angle to prevent sawing the face of the steel angle I start cutting then as soon as the cut is started square up the hacksaw. Cutting takes a few seconds:
element sawn rough size
Then it takes a few seconds more to file the element down flush to the steel angle. Over MANY elements the steel angle will gradually file down in thickness but such a large area and so much harder than the aluminium it will not affect the length between a batch (I checked):
element filed to size
Next to just finish off the end. In the picture above you will notice the countersink bit in the screwdriver handle and a pencil sharpener. Both employed very quickly to deburr inside and outside edges:
element finished end
The only thing left to do is check the length! I am lucky that my place of work happens to have a very large digital vernier. These will do, close enough for G1YBB…
882mm close enough1027mm close enough
Obviously most people won’t have such a measuring tool but it shows the jig can enable accurate results, more accurate than we can normally measure. I belive working as accurately as possible to follow the simulated design will enable the best possible results to be achieved. I have had fantastic results with my first 9 element DK7ZB working to that ethos.

About that lucky error in placement of the angles with the holes…
One thing I forgot to allow for when designing the jig was the driven dipole halves! But by a stroke of good luck (MOST unusual for me) fitting the middle guide hole angle in the reversed place turned out it was perfectly positioned for the dipole half:
driven half cut

I’ll be able make the 432MHz element cutting jig to cater for dipole halves and full elements easily because the threaded bar covers enough length with the 70cms elements being so small.

Simple inverted Vee wire dipole for 50MHz

Now it’s towards the end of June and I have been listening to the other club members I chat and contest with reporting on all the times 50MHz has been wide open on sporadic E, I decided today I would knock up a simple antenna for 50MHz for the garden. My location is not suitable for any real antennas due to neighbour issues so I thought I would make a wire delta beam and mount it fairly low as I have a suitable 2m length of plastic pipe I could use for the cross boom. A quick look at the design scuppered those plans as I had no suitable 75ohm coax here.

I then considered a simple aluminium dipole as I have loads of 1.5m lengths of 12mm tube in the garage. Then it came to me in a eureka moment. A good old trusty inverted vee would be easy to make and do the job nicely!

Since I made my first 20m inverted vee dipole I have since butchered it by cutting off the coax to use elsewhere and it has been lying around the garden for a year or so in the grass in the corner of the garden. Rescue that and put new coax on and I am good to go!
50MHz inverted Vee dipole centre
Next (as seen already above) I needed a pole. I took the bottom 3 sections from my 8m SOTA fishing pole which gives me about 3m of lightweight but stiff pole. In the garden there was fitted a rotary washing line with a two part stem set in the ground. Amazingly it was the perfect fit for the bottom section of the pole! The two sprung plungers even stopping it flapping around:
rotary washing line base section
Into the HF antennas odds and sods box and I got out one of the SOTAbeams lasered guy rings I bought to hang the dipole from. I slid it down to a reasonably but not excessively snug point and wrapped some tape around below that to stop drifting lower and possibly cracking as the plastic is fairly brittle feeling. I also sealed the feed point with liquid insulation tape which is great stuff and taped the coax down the pole to take the weight of the coax, which is longer than I need and only RG223 but I am just looking for something to get on the air and do some tests:
50MHz inverted Vee centre detail
With my HF dipoles I usually peg the other end to the ground with a length of string to insulate and keep the voltage maximum point off the ground but that really didn’t seem a plan. So that delta beam boom was called into play as a dipole spreader:
50MHz inverted Vee close up
It’s literally just lashed on with insulation tape:
50MHz inverted Vee spreader detail
At each end I drilled a single hole to thread the wire through which actually retained the wire quite well due to the tension and angle. But I backed that up with the ubiquitous cable tie. Also visible is a blob of the liquid insulation tape on the end of the wire to stop water seeping up the wire via capillary action:
50MHz inverted Vee end detail
Here is the finished set up ready for tuning. On the left of the image you can see the coax running into my custom wall mount coax connector box:
50MHz inverted Vee
Talking of tuning…
To ‘design’ the dipole I use done of my favourite sites I use for all my HF dipoles over at sotamaps.org. (Click on the 2nd tab for the calculator). I put in the centre height measurement from my set up and adjusted the end support height to get a little under a metre horizontal distance between mast and end support. You can set the wire type via the settings button. You can see it offers me  1.32m for each side. So I cut mine to 1.42m to start as it’s always easier to trim than add!!
50MHz inverted Vee design
First measurement showed beautiful resonance a little under 50MHz, so I trimmed 10mm off each end. Nearly at 50MHz, so 10mm more. Resonant now more in the CW end so I took off another 5mm. The final cut length is actually 75mm longer than the designer suggested, so it could be my  selection of wire should have been for a thinner one or thicker insulation than I chose. (that’s ex red wire with a dose of UV fading applied!):
50MHz inverted Vee SWR trimmings
SWR 1:1, zero reactive component and 49ohms resistive component (50 ohms a tad higher up the band but still in SSB section). I’ll take that!
50MHz inverted Vee SWR
Plugged into the trusty Yaesu FT-857D and a quick scan showed some Es stations calling. Found an EA station and called him, replied to me first time! As did the next 4 stations. Nice one!
first 5 QSOs all one call
So there you go. It is dead easy to get on 6m even with very awkward neighbours and small gardens. 50MHz truly is the magic band when those Es open up too!

Car portable cable access

Nearly all of my radio is done portable in one way or another. When I am car portable like many people I bring the cables in through one of the car windows. As I like to operate both through the winter and in the summer I wanted to keep the cold and rain out in winter and the flies out in the summer.

My simple solution to this is a strip of 1 inch thick closed cell foam with a shallow slit in one edge to fit on the top of the window, and a notch for the cables. Simple but works for me. It also doubles as rattle reducing packing on the way up and back!

car portable cable entry

UK and Europe VHF Contesting Maidenhead Locator Map

With the introduction of the B2 scoring system in 2017 I decided it was time to update my VHF contesting map that I use to help me aim the beam and find multipliers and bonus squares when out portable.

I have beam heading marked centred on my portable locations. They are close enough together at this scale to us just one point.
G1YBB B2 contest Locator map
I usually take an A4 print of this map with me to refer to but the PDF file is fairly high resolution and should be printable at least A3 size at decent quality. Here is a 100% view of the map to see the detail:
100% scale view of detail

You can download it if you wish but if you wanted one centred on your location you can always email me (my email is on the home page here). The annotations are all done in vector layers and can easily moved around to suit. Here is my PDF for a look but it’s probably only any use to David G4ASR and other portable stations in my area.

G1YBB B2 Contesting Locator Map of UK & Europe (15.4MB PDF)

Edit:
However several people have asked for a copy of the map centred on their locator so one of these below may be of use for you. The centre point of the beam headings covers a couple of squares around the actual centre so one near yours. If not you can always email me.

G1YBB B2 Contesting Locator Map of UK & Europe from IO93EG

G1YBB B2 Contesting Locator Map of UK & Europe from IO90WX

G1YBB B2 Contesting Locator Map of UK & Europe from IO92FI

G1YBB B2 Contesting Locator Map of UK & Europe from IO92IR

G1YBB B2 Contesting Locator Map of UK & Europe from IO93KE

G1YBB B2 Contesting Locator Map of UK & Europe from IO90HX

G1YBB B2 Contesting Locator Map of UK & Europe from JO02KM

G1YBB B2 Contesting Locator Map of UK & Europe from IO82PC

G1YBB B2 Contesting Locator Map of UK & Europe from IO93TB

G1YBB B2 Contesting Locator Map of UK & Europe from IO93KH

G1YBB B2 Contesting Locator Map of UK & Europe from JO01JK

G1YBB B2 Contesting Locator Map of UK & Europe from IO70SS

G1YBB B2 Contesting Locator Map of UK & Europe from IO71LX

G1YBB B2 Contesting Locator Map of UK & Europe from IO82RJ

G1YBB B2 Contesting Locator Map of UK & Europe from IO83PN

G1YBB B2 Contesting Locator Map of UK & Europe from IO93MG

G1YBB B2 Contesting Locator Map of UK & Europe from IO93RF

G1YBB B2 Contesting Locator Map of UK & Europe from IO71VO

G1YBB B2 Contesting Locator Map of UK & Europe from IO83MR

G1YBB B2 Contesting Locator Map of UK & Europe from IO91QN

G1YBB B2 Contesting Locator Map of UK & Europe from IO91WP

G1YBB B2 Contesting Locator Map of UK & Europe from IO76XA

G1YBB B2 Contesting Locator Map of UK & Europe from IO70TQ

G1YBB B2 Contesting Locator Map of UK & Europe from IO85NS

G1YBB B2 Contesting Locator Map of UK & Europe from IO92PU

G1YBB B2 Contesting Locator Map of UK & Europe from IO82KR

G1YBB B2 Contesting Locator Map of UK & Europe from IO70UM

G1YBB B2 Contesting Locator Map of UK & Europe from IO86JV

G1YBB B2 Contesting Locator Map of UK & Europe from IO86GB

G1YBB B2 Contesting Locator Map of UK & Europe from JO02MA

G1YBB Contesting Locator Map of UK & Europe from IO83VT

G1YBB Contesting Locator Map of UK & Europe from IO91RU

G1YBB Contesting Locator Map of UK & Europe from JO03AH

G1YBB Contesting Locator Map of UK & Europe from JO02JN

G1YBB Contesting Locator Map of UK & Europe from IO92ET

G1YBB Contesting Locator Map of UK & Europe from JO01EF

G1YBB Contesting Locator Map of UK & Europe from IO84JX

G1YBB Contesting Locator Map of UK & Europe from JO01JP

G1YBB Contesting Locator Map of UK & Europe from IO83SB

G1YBB Contesting Locator Map of UK & Europe from IO74AU

G1YBB Contesting Locator Map of UK & Europe from IO81AS

G1YBB Contesting Locator Map of UK & Europe from IO91CL

Portable 6 element 50MHz DK7ZB long yagi

Towards the end of 2016 the rules and days for the UKAC series of RSGB contests were changed. The 50MHz and 70MHz UKAC events were moved to the 2nd and 3rd Thursday of the month respectively. This opened up more opportunities for me as working a Tuesday night contest means rescheduling my Tuesday to a Wednesday and means my Wednesday is busy as heck and it’s at least Thursday before I can even look at the tablet to get the log updated. But a Thursday I am usually free so I can get on another band. As I have no 70MHz Tx capabilities I decided 50MHz was the way forward for me. I have an old home made 5 element yagi we used to use but I wanted a newer better performing yagi. I am getting awesome results with my 144MHz 9 element yagi I decided another DK7ZB sounded ideal.

I chose the 6 element 7.2m boom version as I plan to only use it car portable and it’s only 1m each end longer than the 144MHz yagi I’m using. Also it has a great SWR curve. All dimensions are available on Martin DK7ZB’s site:
6 ele DK7ZB yagi dimensions
This design only had figures for 12mm elements. That was OK as I can get 12mm pipe clips like I used in the 144MHz yagi. But it turns out buying 12.0mm tube in lengths greater than 2000mm in the UK is exceedingly difficult. It had been suggested to me to use 12.7mm tube as that would be easy to buy in the UK but would require recalculating the element lengths. Not only that it would prevent me from being able to use the fast fit pipe clip I wanted to use. After much searching and asking in various places I had to admit defeat and arrange with Attila at nuxcom.de to ship (at some considerable expense) some 3000mm lengths of 12mm tube, along with several other antenna parts and also some 3000mm lengths of 10mm element tube.

For this yagi, unlike the 9 element for 144MHz, I had no plans to take it backpacking portable so I decided it only needed a 2 part boom. I was easily able to get 5000mm lengths of 20mm boom for this. 20mm is quite small sized boom for a yagi of this size but my element mounting plates are designed for 20mm boom only. I’ll be using truss supports and side supports if required to stop it flexing too much. The 5.1m long 2m yagi was nice and sturdy with its trusses in high winds on the top of the Black Mountains. Although it’s only 1 metre longer each end, it makes for a big boom!
7.2 metre long boom
Once the element positions were marked up the 5 parasitic element clips were fitted in the same manner as the 144MHz 9 element. On this yagi the driven is too big for the element clips so that will need a more conventional box:
element clips fitted to boom
For the feed box I decided to go for a beefed up version of that I did with the 144MHz 9 element. I chose an ABS box from Farnell as it is quite thick walled and with a decent lid should be pretty stiff and is also IP65 rated (before I start drilling it). In order to get a suitable height so the driven element 16mm sections could be on the same plane as the parasitic elements it came in quite large at 200 x 150 x 55mm but that is OK as the driven on this 50MHz is quite big:
Farnell 1526658 box
Here it is marked up for drilling. Marking needs to be spot on as this is what makes the driven element parallel with the parasitic elements in both planes so is crucial!
driven box marked for drilling
This is the centre point of the dipole box used for locating it on the boom in exact position:
dipole box centre locating hole
To enable stability and strength for the 3 metre driven element I am using some 19mm angle. The sighting hole above lines up with the centre of the scribed line:
dipole box supporting angle
To mount the two halves of the dipole I got my good friend Paul to 3D print some two part clamps in ABS to my design so the centreline height of the driven element above the boom matches the parasitic elements so all elements are in the same plane. Here are the clamps after drilling and fitting to the box with some 16mm tube to check alignment:
driven element clamps fitted
To fit the dipole box I drilled and tapped an M2 hole in the centre point of the boom on the scribed line as seen above and screwed the dipole box in place using the 2mm sighting hole. I then fitted the reflector and first director and ensured they were all parallel and drilled the box to fit the two angle pieces:
fitting dipole box to boom
When I bought the element materials from nuxcom.de I also bought their dipole centre for 16mm tubing:
nuxcom 16mm dipole centre
Which is very chunky and strong. But the 16mm tubes fit inside the joiner and I couldn’t see how one would get a good secure contact to the elements. So I got another good friend Ed to turn up a piece that would fit inside the elements like the nuxcom one for 10mm elements does. Here is the mechanically finished dipole centre:
finished dipole centre
The eagle eyed may be wondering what the red things are in each end. Well as I am using jubilee clips to clamp the 16mm tubes down onto the 12mm main driven element parts, once they are removed for transport (this yagi is for portable use remember) the jubilee clips are free to fall off unless clamped down. So my I got some plugs 3D printed to clamp onto to retain the jubilee clips and also prevent any dirt ingress during transport and storage:
jubilee clip retainer plugs
Now the dipole needs the DK7ZB match. I’m using the same WF100 75ohm coax I used on my 144MHz DK7ZB, which is fairly low loss for its size, and is not too big or heavy. Its claimed velocity factor is 0.85 so I worked out the length as so:

300/50.150 = 5.982m full wavelength
5982/4 = 1495.5mm for quarter wave
1495.5 x 0.85 = 1271mm

As before I used a section of boom to tame the curling of the coax to allow accurate measurement and cutting of the lengths:
making the DK7ZB match
DK7ZB match one end
DK7ZB match other end
One end of the match fitted:
dipole wired to DK7ZB match
A picture of the process in operation in the ‘workshop’:
the G1YBB construction workshop
Other end of the DK7ZB match completed:
coax feed box
Apart from the bracing the antenna is pretty much complete except for the fact that the element mounting plates are not really man enough for 3 metre long 12mm elements. They were designed for the 144MHz yagi and only 1m long 10mm elements, which they are perfect for. With the larger elements this is how they were flexing with gentle persuasion:

A quick chat with Paul and he drew up a two part brace that he could 3D print me and soon they were in the post!They utilise the same holes already in the element plates and wrap underneath adding strength without interfering with the element clips at all. I used M4 nylon screws to add extra fixings without adding extra metal, the only metal nut and bolts holding the element clips on:
element plate brace fitted
After fitting the new bracing parts this is the flex with quite boisterous provocation:

Much better!

My next consideration is bracing. Long supports were made and fitted utilising the same fittings as on the 144MHz yagi. In fact as I write this I have started work on a 70MHz yagi. All three will fit on the same fittings on the portable mast, and the 70MHz yagi will re-use one of the 144MHz yagi braces and one of the braces for this yagi. The angle of the supports is quite narrow but they do support the boom and keep it straight. This yagi also will need side guys to protect it from the wind. I have several bottom sections of 4m fishing poles left over from HF antenna projects so I utilised two of those. Again Paul quickly produced some parts for me. Some ‘plugs’ to fit to the mast plate to mount the poles onto:
side guy pole fittings
And some stoppers to go in the end of the poles for the 3mm dacron cord, which is very strong and has very little stretch. The stoppers are a good interference fit:
side guy rope stoppers
side guy with rope fitted
Side guy poles fitted to the mast. These are a friction fit to the ‘stoppers’ and quickly assembled on site:
side guys poles fitted
The sides guys clip onto a plastic bushed (thanks Paul!) bolt on the boom supports with a single karabiner each end. Very quick to deploy:
side guys and supports fitted
Next step was to test it! This was done after work on the Wednesday before the first 50MHz UKAC in Jan 2017 the following day! It was reading 1:15 throughout the SSB portion of the band, which was slightly disappointing. There was no time to look into this as I needed to get back home (testing was done in a mountain’s car park) and pack for the next night’s contest!

On the night of the contest the in radio SWR reading was quite low so I was happy the radio was feeling OK about the match and used the new antenna for the first 50MHz contest I have done in 20 years. The yagi seemed to work pretty good and I even managed to beat G4CLA in the AR section of the RSGB 50MHz UKAC January 2017, which I was delighted with!

This is the only photo I have of the yagi on a mast so far, I’ve not seen it fitted in daylight!
first test of 50MHz 6 element DK7ZB

Updates to portable car table

I have been using a piece of ply for years as a car portable operating table in many cars and still do, described here:
http://g1ybb.uk/simple-car-portable-operating-table/

After I made a post on the UK VHF Contest group on Facebook I got a reply from Dave G3WCB showing his cool car portable setup. I had already very recently thought of doing something similar but seeing his setup gave me an idea for a simple and quick update to my plank of wood.

I already locate it over the steering wheel for some security to stop it toppling over and trashing my radio gear but seeing Dave’s set up I realised I could secure the other end with two simple locating pegs and make it virtually idiot proof. Out with the 3D design and quickly knocked up a tapered peg to fit the headrest sockets. I included a recessed hex to take an M4 nyloc to save having to over tighten a bolt onto wood and split it:
3D modelled headrest peg
Shortly sent the file to my very generous friend Santa Paul who 3D printed me some and they were in the post!

A quick measure in the car and drilling and job done:
pegs fitted to board
Fitted to top of driver’s seat:
fitted ready to use
Just needs a radio and rotator controller:
ready for radios

144MHz 19 element MET yagi antenna

Having recently built one of the new (to me) DK7ZB designed yagis for 144MHz I am finding it’s performance to be amazing. It even feels like it performs better than our old array of 2x 19 element MET antennas. So I wondered how they measured up for gain.

The 19 element MET antennas we used back in the 1980s and 1990s and Google was struggling to come up with the good for me to see what they were specified as to compare. I eventually found this advert in a PDF for a construction article from a 1983 Practical Wireless magazine so I thought I would share it for anyone else who might follow the same path.

MET yagi antennas
So our 19 element MET yagi was 14.2dBd from a 6.57m boom.
My new 9 element DK7ZB is 12.5dBd from a 5m boom.
To get 14.2dBd in a DK7ZB requires a 8m boom. Hmmm.

I’m not sure I fully trust the claimed gain on this advert! 14.2dBi maybe, but I am not convinced on 14.2dBd. The ‘feel’ on the air of the new single 9 element DK7ZB is just great comparing to what we used to work on the 2x METs. I am getting great signals from familiar places and people. I am using a new-ish radio (FT-817) though that is not what I would call a top spec VHF contest radio. I am using a lower mast and probably better quality and shorter feeder I guess. I must dig out the Yaesu FT-225RD I used to use and see how it ‘feels’ on that. One thing I have thought of is I know we mounted one MET at top with support below, and one at bottom with support up. I can’t remember if we arranged the feeds to be on same side! So we may not have been operating as efficiently as possible.

All in I am loving the DK7ZB and can see why lots of the contest groups have them.

Simple car portable operating table

As I have always operated way more as a portable station than a base station I have operated from the car many times and in many ways. Some not as comfortable as others that’s for sure. It gets tiring twisting to one side or hunching over. In the end I came up with a simple solution for me that enables me to easily set up and have space, and be comfortable operating, which is important if you are spending a long time operating like in a contest.

Basically, a plank of wood!

More accurately it is a small sheet of plywood sized and modified for purpose to make a flat table in the car to carry the radio and any ancillary units like batteries, PSUs or amplifiers etc. It’s strong enough to support a 4CX350 based 200W VHF amplifier.

The sheet is sized wide enough to fit in most normal cars and long enough to reach from the top of the dashboard to just past the back of the driver’s seat. There is a slot cut to allow it to slip over the steering wheel:
car portable operating table
I keep it in the boot ready to go as it doesn’t really take any space. I just take the head rest out of the driver’s seat and sit the board on the top of the seat. The slot for the steering wheel allows the board to sit on top of the dash and adds a level of security from catching a sleeve on a corner and knocking it off. In my shiny new car I just add a towel over the steering wheel and dash and another on top of the seat to protect them from any markings. The two head rest entry points and top of the curved dash make a tripod style stable platform. And the weight of the radio and batteries keep everything steady.
I use my backpacking batteries because I don’t have a DC feed at 20A to the car battery for the radio and I don’t have to worry about draining the car battery if a pileup comes my way.

I pull the steering wheel all the way forward to drive anyway, but this means the wood extends back enough to sit normally in the back seat without even moving driver’s seat and I can sit with my back against the back seat (rather than hunched forward) comfortably and operate. In fact these days as you see, I have the tablet on my lap. The most comfortable car portable operating I have found, and I have done a lot over the years!
car portable operating table
This is about the 4th or 5th car this board has seen action in and it is now into it’s 4th decade (with about a 2 decade break).

DH8BQA voice keyer BX-184 for FT-817, FT857D, FT-897D mic MH-31

I was scrolling down my Facebook feed and spotted a post in I think one of the SOTA Facebook groups mentioning a BX-184 CQ Parrot. It looked interesting at first, then awesome! Within 20 minutes I had it ordered.

This is a modification to the standard MH-31 microphone that comes with the FT-817, FT-857D and FT-879D etc. It will record and playback a message, perfect for calling CQ Contest or CQ SOTA etc, but without the requirement to carry and connect up another gadget as it fits completely inside the microphone body. It was designed by Oliver DH8BQA and he describes it on his website here http://www.dh8bqa.de/bx-184/.

It is available for sale on the German Funk Amateur site here Funk Amateur BX-184. However they also do another kit that includes an MH-31 microphone body if you don’t want to disturb your original mic and that is the option that I took Funk Amateur BX-184M. The website is all in German so if like me you don’t speak German Google Translate will help a lot! There is also now a USA vendor here http://www.box73.com/product/2

It came pretty quickly and this is what you get in the box:
what is in the box
A complete kit with all you need. The PCB is part SMT (surface mount technology) and part through hole components. You just need to fit the through hole components.

The double sided PTH PCB is very nicely built.
Top:
PCB as supplied top
Bottom:
PCB as supplied bottom
Before it arrived I did some research and found some mods made by DG2IAQ on eHam which sounded worthwhile:

Mod 1:
I do always replace C8 (4,7µF) by a nonpolarised SMD 1,0µF to fasten up the AGC. With this Change the internal AGC works more as a mic compressor than as a (slightly delayed) mic Level limiter.”
Mod 2:
And for the first time I changed R4 (82k) into 56k to bring the sample rate from 8kHz up to 12kHz (by a shortened play time of 40s instead of 60s, but that’s still more than enough for my needs). This change gives even more punch for the replayed calls as the sound is a little more high-pitched afterwards. You simply can solder a 100k SMD in parallel to R4 instead of completely replacing it.”
I emailed Oliver DH8BQA for his thoughts on these mods and he confirmed they should be worthwhile.
So I decided an 0805 ceramic chip 1µF capacitor would fit best across the pads for the 4.7µF electrolytic it was replacing:
C8 fitted as 1uF
I should have fitted this first as the 15µF cap next to it made it awkward to get a good solder joint on the GND side of the capacitor due to the ground plane wicking the heat away. Got there in the end though:
1uF cap fitted
R4 is an 82K 1206 sized resistor located on the rear of the PCB (this is easy to locate as the kit comes with build instructions in German with a good circuit and layout supplied. English instructions can be downloaded here, page 5 onwards English Build Guide):
standard R4 as 82K
And with a 100K 1206 fitted in parallel (on top of the fitted resistor) as suggested above:
R4 with 100K added
With all parts now fitted (including a 1206 capacitor fitted across the supplied electret insert terminals) all that is left to do is mount the electret insert into the microphone body and solder that to the PCB.
Opening up the supplied microphone and removing the PCB revealed these 2 slabs of steel in the body. The only function of these I could see was to add weight to make it feel more substantial. So I got rid of those. No point in carrying dead weight:
empty mic shell
Next I hot melt glued the electret insert into the mic and filled up the void as the instructions said. Actually I filled more than the picture in the build instructions showed by mistake. Then solder the screened cable to the PCB and fit the IC and it’s ready to be assembled:
finished prior to assembly
As the replacement PCB does not have the two position slide switch, there is the unused hole in the back of the mic. For this I just used some good quality sticky label material I have to hand.
One piece inside:
switch hole covered up
And one on the outside.(not pretty but functional):
switch hole covered up ext
Once assembled I compared the standard supplied Yaesu MH-31 mic for weight against the BX-184 CQ parrot. A 40% saving in weight, I’ll take that:
Yaesu MH-31 v CQ parrot weight
I soon connected it up to the radio ready to go but there was no outgoing audio! What!? With several projects on the go I could do without time spent fault finding. What if I have cooked the electret soldering the capacitor on now it’s well and truly hot glued into place. Hmmm. Hold on, what was that pot trimmer for? I remembered when building it I couldn’t see any mention of it. A check of the circuit confirmed the obvious answer. It’s on the mic output to the radio. A quick check with the meter confirmed it was currently set to ground the mic line going to the radio. A quick tweak and we are back in business.
In fact the worst part was setting up to monitor myself. Eventually I had a reasonable system, FT-857D on 5Watts into a dummy load near the FT-897D with a 4mm banana plus as an antenna feeding into the sound card on the PC, with Audacity dealing with the recording. The recordings are not broadcast quality but are good enough for a comparison.
Here is a CQ call using the standard MH-31 mic:

Here is same CQ call live using the BX-184:

And the replayed recorded CQ call from the BX-184:

I might need some on air radio reports for final setting but it doesn’t seem to be clipping at all though does have a little more punch.

 Can’t wait to try this out in a contest or SOTA activation. All in a great little kit well thought out and went together very well. The only small point is no actual mention of the trimmer function or setting which would be good as a reminder if nothing else. I know this kit is aimed at radio amateurs who should be able to look at the circuit and deduce why the pot is there so this is a very minor point in a great kit.
Edit:
I have since used this ‘in anger’ in 144MHz contests. The first contest I got some complaints about over driving and being wide (complainant was also wide to me for that matter!!). But I turned SSB mic gain down in the FT-817 and back at home I did turn down the audio output level on the microphone itself and did some tests between it and the standard MH-31. Subsequent contests have resulted in zero complaints but some good audio reports.

Lightweight Yagi beam element mounting plate

In order to facilitate the building of my backpacking lightweight 144MHz 9 element DK7ZB yagi with a friend I came up with this reinforced plastic element mounting plate.

The primary idea behind it was that it would make it easy to accurately position elements in the right position along the boom and also ensure the elements were mounted nicely perpendicular to the boom. This was the sought after benefit for my build, ensuring all elements were nicely parallel to each other and in the same H plane. Also it would allow easy use of specific element mounting methods particular to my variation of a DK7ZB 144MHz long yagi beam design. The mounting plate is specifically designed to work with 20mm square section boom.

Here is the 3D design of the element mounting plate:
element mounting plateAnd a dimensional drawing for suitability to other yagi build applications:
yagi element mounting plate
For my beam (linked at top) I was able to use this to mount both parasitic elements and the custom driven element:
element in numbered location
finished DK7ZB match
The element mount plate has location ridges underneath to align perpendicular with the 20mm square boom and has a small central sighting hole to align with a marked up boom for element centreline positions:
element plate fitted
Two fixing holes are provided to fix the element mounting plate to the boom. They are sized for 3.2mm pop rivets but can be easily drilled out for other sized bolts or rivets. The element mounting clip holes provided can also be easily enlarged. They are supplied undersize for M3 deliberately so that an M3 bolt has to be screwed into them thus providing a precision centre aligning of the bolt and hence element clip mount.

Here is a video of the element mounting plates in action:

The clips have now been made available for other radio amateurs wishing to do a similar build in sets at
https://imlmoulding.co.uk/yagi-beam-element-mounting-plate-lightweight/