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Topband: Wired/wireless Beverage hub progress.

Subject: Topband: Wired/wireless Beverage hub progress.
From: Pete Smith N4ZR <>
Date: Wed, 22 Feb 2012 17:16:09 -0500
List-post: <">>
I hooked up the hub today, and initial results are excellent.

For those who missed earlier messages - here's the story.  I ran across 
an inexpensive 8-way relay board on E-bay for less than $20.  It is 
controlled by a 300-MHz radio remote, and I figured I might be able to 
use it for remote switching of receiving antennas.  Rather than try to 
boost the radio control signal with a directive antenna, Ian, GM3SEK 
encouraged me to experiment with coupling the RF from the remote to the 
350 feet of coax out to the planned hub location, using a 1-inch loop at 
each end.  It worked!

As with many such projects of mine, this one mushroomed a little bit.  I 
added a 20dB ARR preamp at the hub, using DC sent to the hub from the 
shack with a DC bias tee, which was needed for the relay board anyway.  
Rationale for putting it out there, rather than in the shack, was that I 
plan to use low-output antennas (BOG, K9AY, etc.) and wanted the desired 
signal to be as loud as possible relative to any common-mode pickup on 
the feedline.  I also used a super common mode choke near the hub, per 
ON4UN and K9YC.

Since I only had one good 9:1 binocular transformer, I decided to share 
it among the antennas that will be connected to the hub.  A little 
fiddling with TLW and various impedances and reactances convinced me 
that the extra cable loss caused by mismatches will be quite manageable 
for 160 and maybe 80 meters.

I was worried about isolation between antennas, because the relay board 
was not designed for RF, but early indications are positive.  A local 
broadcast station, on 1550 KHZ, is S9+60 on the BOG, and just S9 when I 
switch to an unused terminal, even the one physically adjacent.  Signal 
level is only slightly below that received on my shunt-fed tower

Now to build a proper control unit - For $18.50 I'll buy another relay 
board and use it with push-button switches and LEDs to display which 
antenna is selected.  Thanks to Grant, KZ1W for this suggestion!

I'm curious - does anyone think there would be enough interest to 
warrant writing this up for one of the mags?

73, Pete N4ZR
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