[TowerTalk] Building a W6NL Moxon 40 Meter Beam.

[L L bahr]

As mentioned on another post and subject,  I am going to build a 40 meter W6NL Moxon Beam. The center of the Director is split and is not at ground potential. I see a lot of builders have used a two foot long aluminum channel to mount the Director and Reflector to the boom. They use a plastic or fiberglass sleeve to isolate the director from the grounded Boom. I can see this would make for a very strong support.

1.  All this to me means, 2 foot of the radiating part of the Director is close coupled to ground.  I'd think this is Bad!! Seems to me the use of a Delrin spacer rod or fiberglass sleeve with just the use of U-bolts without the 2 foot of aluminum channel would dramatically reduce the Director coupling area to the grounded aluminum channel.  

2.  Also, the feed point on all the versions I have looked at couple an RF choke right to the center point area of the Director.  When I built a couple plain Yagi antennas, I used a Gamma Match or T match thus tapping the Director element at a 50 ohm point rather then at say at a 15 ohm point or so right at the center of the director.  Why is this not done on the W6NL building examples?  Is it because they think and hope the RF balun choke is going to keep the mismatch SWR in check?  Can anyone explain this to me? I'm not sure, but I suspect the impedance right at the center of the Director is not 50 ohms or even close to being 50 ohms.

Anyway,  I thought I would throw these two concerns out for you experts to comment upon. Am I thinking clearly and correctly or am I wrong somewhere?

Lee, w0vt
Houston