[NLRS] yagi newbie questions

[Aaron David Lewis]

Thank you everyone for your excellent responses.  Video, tips, etc clears up a lot and I will save this thread. I wish I had room for the 21' boom :)

I should make the next Maple Grove breakfast by the way, but I'm not sure if I'll have something to bring yet, but I'd be happy to look at your examples.  I definitely want to work the next VHF contest on more bands.  I did my first rove with K0DJD back in the Fall as K0LTC/R and I'd say we did OK for barely knowing what we were doing 😉.  We got first in Dakotas division.  I guess we were lucky to enter the right class.

Aaron
________________________________
From: Doug Reed <dhreed55109 at gmail.com>
Sent: Wednesday, February 28, 2024 14:17
To: Aaron David Lewis <W0ADL at outlook.com>
Cc: nlrs at mailman.qth.net <nlrs at mailman.qth.net>
Subject: Re: [NLRS] yagi newbie questions

Hi Aaron.

<https://www.youtube.com/watch?v=QCxpaCAhj3Y>
There are many web sites that show how to build a VJB wood beam. So
you should be able to answer all questions with a little research.
Where the directions talk about gluing the elements, it is referring
to gluing the element into a hole in the wood boom to prevent it
sliding out in the future. You could use black zip ties on the element
on either side of the boom instead. You want to use a non-conductive
boom such as wood or plastic. The simple option is a length of 1x2
pine or a good hardwood if you want it to survive longer. Perhaps use
the cheapest material for the first version and build a second one
later on if you decide to keep it. I prefer a penetrating wood
preservative like Thompson's Water Seal or 50-50 mix of turpentine and
boiled linseed oil. Other people have used stains or paint.

NLRS does antenna gain measuring at the Aurora Conference in June.
Experience over many years has shown that if you build a VJB antenna
according to the dimensions in the articles, it will work as
specified. If you decide to "improve" the antenna, it will probably
not work. So build your first antenna according to the articles. Save
your improvements for later. The important bits are to use the boom
material as specified and no thicker, and use wire elements of the
correct diameter. The driven element needs to be something you can
solder to, the rest can be anything conductive and cheap.

RG58 will work for the short jumper but I usually end up melting the
center insulation. I'd recommend deciding how long a pigtail you want,
then buy a jumper cable using RG400 PTFE coax with N-female crimp
connectors, then cut the cable in half and solder to the driven
element. You are building antennas for 420MHz and up, so they should
have N connectors and never use UHF connectors. You can probably find
suitable jumper cables on Ebay. I'm still unsure what is the best way
to water seal the braid going into the cut coax end.... Maybe a thick
Crazy Glue, a thin epoxy, or liquid electrical tape, all covered in
silicone rubber?

The main adjustment you can make is to squeeze or expand the loop
spacing of the driven element. You can also bend the driven element
slightly closer or further from the first director as a final
adjustment. That will slide the tuning around until you have the best
SWR exactly where you want it. But it should work pretty well without
tweaking. If you are going to play around with building antennas, you
might want to start looking for a NanoVNA to use for antenna
adjustments. A cheap NanoVNA starts around $50 and goes up from there.
You WILL need some work to understand how to use it, but YouTube
university will help with that. You could always ask to meet with
someone after the monthly breakfast meeting and do a quick check in
the parking lot. Just point the antenna straight up in the air while
adjusting for best SWR.

73, Doug Reed, N0NAS.
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