VPA Systems tri-band 10m 6m 4m moxon + yagi test review

As an avid antenna constructor myself this is a bit of an unusual post for me. It comes around as I was planning to build myself a dual 10m and 6m beam based on the DK7ZB design on this page (link). I was already running late as the Es season was well underway and in chatting with the Hereford club members Clive G8LNR said there was a tri band version of the same thing doing nothing I could borrow. It was made by VPA Systems and sold by TelTad on this page (link). This was ideal for me as it would save quite a lot of time, so I leapt at the chance and fetched it to my house to build.

This is a lightweight budget end of the market antenna with a claimed weight of 3kg and costing 193€ but that is ideal for my purposes. I retract my mast to gutter height when not in use and I don’t want heavy antennas on the aluminium mast (I’d love the Optibeam OB6-3M but it’s just too heavy).

Unravelling the bundle gave me this set of parts:
supplied parts kitwhich includes a set of Stauff style element mounts, stainless fittings and a single U bolt for fixing boom to mast. continue reading

Some great mast guying tips

Some great mast guying tips……in my humble opinion of course!

I love guy ropes. All masts are just so much safer well guyed in my opinion.

I recently made my own 3 section aluminium winch up and luffing mast for the base station (must detail that one day!) that needed guys for my own peace of mind.  So I wanted some good secure ways of keeping is safely guyed when up and retracted. So the below is what I came up with with some experience in other hobbies and some research. I’m really pleased with it so thought I would share.

Anchors.
The garden is very small and fully paved but does have a 6 feet or so brick wall on two sides and a concrete post on the 3rd that I could use to guy to. So bolting a fixing to the wall was the obvious answer. I’d already bolted some eye rawl bolts in before but they were too small for the snap links I wanted to use and they didn’t fill me with 100% confidence. What came to mind as the perfect solution was bolt on hangers used in climbing walls for clipping the top ropes into. I could then bolt through the bricks and it would be bombproof. They look like this (though I would be using them upside down as our ropes go up not down!):
Petzl coeur hanger stainlessI got stainless ones from Needlesports here (link) for under £3 each as they will be outside 24/7. continue reading

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. — continue reading

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: continue reading

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 continue reading

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… continue reading

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: continue reading

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. continue reading

Yaesu FTDX-5000 transport case

THIS IS NOT A FLIGHT/SHIPPING CASE!!
This is a FTDX-5000 transport case for things like taking it to field day etc.

As the FTDX-5000 is an expensive and heavy beast I designed and made a transportation/storage case to fit it. I’d looked at what you could buy and everything was huge and heavy, increasing the size of the 5000 by a considerable amount. Something simple, low profile and low weight was required.

Images are clickable for larger version.

Below is the resulting case. It’s powder coated aluminium, adorned with protective foam so the radio never gets scratched or dusty/wet (just care fitting the lid is all required) and has latches to quickly but securely lock the lid on. Once in the case it can be carried around without fear of accidental bumps, things falling on it, kids fiddling or rain (to and from car etc).
FTDX-500 transport case

The box is designed to enable the radio to be operated whilst still in the base, and even offers a handy place to hang the standard microphone: continue reading

Plugging yagi dipole ends to waterproof them

When making my yagis I prefer plugging yagi dipole ends so water cannot run down the tube and enter the dipole housing with its corrosive end results. Also, it does stop spiders moving in and making a right mess everywhere.

Many people do not like to add caps to the elements for concerns over altering resonance, so I just cut the cap off and push them in so they are fully inside but water cannot enter. Simples.

plugs for yagi dipoleThese plugs were from nuxcom.de but he has ceased trading now but they are available at various places including Tino’ Funkshop but these days if you are in the UK it’s best to look more local.