Dual Band Yagi

Happy Days! I have a new dual band Yagi; 3 Elements on 2 and 5 on 70 fed from a single N-Type socket on the boom.
I stumbled across this while scanning eBay for a suitable H.F. set to use as a remote station that is to be permanently operational from my alternate location in South Western France.

Brief Technical Spec
  • Type: Dual band 3/5 element yagi
  • Frequency: 144-146 and 430-440MHz
  • Boom length: 115cm
  • Longest element: 100cm
  • Gain: 9.5/12.5 dBd
  • VSWR: 1.5:1 or better
  • Power: 100 Watts
  • Connection: N-Type female
  • Weight: 870g
Putting it together is easy... nearly!

The assembly instructions are very basic, filling just one side of A4, but you really don't need them for the majority of the build. As can be seen in the middle image above, both the boom and the elements are colour coded making it a breeze to put together.

The only slightly complicated part of the assembly is installing the coupling bars from the connector block to the driven elements. I managed to get them the wrong way round resulting in quite horrible SWR! A quick glance at the instructions once more and I immediately saw my mistake and swapped them round. You would have thought that it was blindingly obvious that the long one was for VHF and the sort one for UHF... I guess it's pays to read the manual after all :o)

SWR Adjustment and First Contact

My test mast is a heavy duty, photographic lighting stand and it telescopes up to around 20ft or so. Into the top of that I drop a ¾ inch dowel and attach the antenna to that. I've used the test mast for several projects over the last 12 months and it's proved invaluable. Keeping test and prototype antennas away from the ground and buildings makes adjusting and evaluating them so much easier.

First contact goes to Richard, G6VGC. While he's not a million miles away from me here in Stoke, Richard is far enough (18-20Miles) to make a good evaluation on VHF of the Yagis performance. On the back of the beam, signal strength was very poor and would be considered unworkable. Side on was acceptable at around S2 but front on, pointing directly at Richard by "peaking his signal, and a really good S8.

It's my intention to take the test mast up the hills in the car at some point in the near future... I'll post an update with the results when I have them

Conclusion - 9/10

All in all, very happy with my purchase and it's a definite recommended buy from me. Not just for the fact that it's a dual band Yagi but the build quality is second to none and, as it's all stainless, it should last a long, long time. It would have got 10 out of 10 but I'm missing a pack of spring washers that are supposed to go behind the wing nuts... I'm not worried as I have them in stock but, never the less, they should have been in the pack.

I'm sure they are available from many places but, if you are interested, I got mine from "moonrakereu" on eBay.

Update - 20/07/2014 - Quick Change H/V Mount

Having been up the hills and tested the dual band Yagi, one obvious design flaw, when used portable, is the need to carry a spanner if you want to change from horizontal to vertical or vice versa.

Having spent a few minutes coming up with a fix, followed by a quick trip to a local DIY shop, Hey Presto... a quick change mount allowing very simple setting of the desired polarity.

I used a 25mm plastic conduit Inspection Tee slid on to the boom and padded with a couple of split rings of 20mm conduit to provide a bearing surface. This allows the square boom to rotate in the round conduit and the Yagi can be twisted from vertical to horizontal, and back again, in just a few seconds without the need for spanners or screwdrivers.

An extra "bonus" is that the Yagi is kept clear of the metal mast via length of 25mm plastic conduit, acting as a stub-mast, connecting the Inspection Tee to my portable telescopic stand.

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