[NLRS] Club Cheap Yagi Build Day Advice Needed

[WA2VOI, Donn]

Hi Bill.

Good for you to head the effort up.  I think it will be more than worth the effort!

As for element material, you're correct... getting welding rod >36" is hard if not 
impossible.  Try looking at one of the metal places on N 2nd St along the river in 
Minneapolis.  Garlick near the corner of Broadway and Discount Steel at the corner of 
27th.  They "should" have 3/16 Al rod at reasonable prices.  Most likely cheaper than #6 / 
#8 Cu from Home Despot.  (Check prices though, at all three !)

1/2 x 3/4 pine is called "parting stop" and is a bit too small for a 2m version.  You 
certainly can't drill cross holes in for 1/4" U-bolts.  Try looking for "1x2" pine, which 
is 3/4 x 1-34"  The extra height doesn't cause a problem and its still 3/4" thick.  Lots 
of room to drill holes for horizontal mounting and thick enough (3/4") for holes for 
vertical mounting also.  Make the distance behind the Ref l-o-n-g so you have room to 
drill holes.  You should be able to overlap them by 1/2 distance between the U-bolt 
spacing, but you can't overlap the holes themselves.

I would recommend giving the finished antenna at least one coat of varnish.  They'll last 
longer.

The bottom portion of the driven element (the bottom of the 'J')  will be very floppy and 
you'll be tempted to add a piece of wood to lay the element along to stiffen it up.  DO 
NOT.  The added dielectric will lower the resonance of the DE in an unpredicible way.  If 
you HAVE to do something to keep the DE looking like a 'J' find some thin fiberglass stock 
(look at Ax-Man... they had some 3/4" x 1/8" fiberglass bar stock) and make a couple of 
spacers out of that.

If primary use will be FM (ex. w/handhelds), AND you can accurately measure SWR, you might 
want to shorten the element lengths 1/2"  That will move it up to the FM portion the band. 
Build one, cut a little bit, MEASURE, and repeat if needed.  Don't try for perfection. 
1.5 : 1 or so is "good enough."  (Remember a good dummy load has a 1:1 SWR... but its not 
much good as antenna.)

Unless you have or can borrow the correct crimp tool for the connectors, I'd recommend 
using good old solder PL-259 with the CORRECT reducer insert for RG-8X/LMR240 or RG-58. 
If you need to get to BNC, use a PL259/BNC adapter.  You're right about many (most ?) not 
having 'N' connectors (unless SERIOUS 2m people and running power).

Jim's comment about writing the final SWR and dimensions on the boom is a great one... 
wish I'd though of it !

Good luck !!

73 Donn
WA2VOI/0
----- Original Message ----- 
From: "W. S. Mitchell" <wsmitchell3 at gmail.com>
To: "NLRS Reflector" <nlrs at mailman.qth.net>
Sent: Wednesday, November 16, 2016 1:14 AM
Subject: [NLRS] Club Cheap Yagi Build Day Advice Needed


>
>
> Greetings,
>  I am organizing a WA5VJB Cheap Yagi build day for the Bloomington
> (MN) Amateur Radio Association, which will happen at some point in the
> next few months.  However, having never built these antennas before, I
> could use some advice.
>
> Assume for a moment that there are 8 participants, each of whom is
> interested in building a 3-element 2 m yagi.  Each antenna requires
> roughly 12' of conductor, with lengths of 37" (director), 41"
> (reflector), and 60" (driven).
>
> Am I correct to think that the best way to approach this is to use #10
> solid copper wire for the whole thing?  I've looked for welding rod,
> and it seems like it's more suited for 222 MHz and above (hard to find
>>36" pieces).  From my searching, 1/8" or 3/16" copper tubing are a
> bit tricky to find as well, and is generally more expensive (and less
> robust in the field) than the (admittedly thinner) solid stuff.
>
> My hardware store has 1/2"x3/4" pine in 8' sections, which should be
> good for a few antennas.  I already have coax that can be used, and
> tracking down crimp-type connectors (BNC, PL-259, probably not N
> because the club members are unlikely to have any N gear) shouldn't be
> too difficult.
>
> Any advice or suggestions on sourcing materials would be greatly appreciated.
>
> Thanks,
>  Bill
> AE0EE
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