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Re: Topband: Where to place a preamp? Switching Beverages?

Subject: Re: Topband: Where to place a preamp? Switching Beverages?
From: Don Kirk <>
Date: Fri, 20 Jan 2012 12:08:56 -0500 (EST)
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N4ZR said : I have a 20 dB ARR preamp", "My choice is whether to put it at the 
antenna end, incurring the added complexity of sending 12V DC to it via the 
coax, or to put it in the shack."

Per the ON4UN book, "In most cases you can put the preamplifier in the shack.  
The signal loss in the feed line is a loss that affects both the signal and 
external noise.  That means that the loss in the feedline does not affect the 
S/N ratio."

I personally have 3 point fed pennants that are very small (51.6% the size of 
full size pennants), and therefore their gain is around -46dbi, and my preamp 
is located in the shack (W1FB slightly modified preamp).  I've done some simple 
tests with my preamp out at the feedpoint versus in the shack and I personally 
was unable to detect any difference in S/N performance but my measurement 
system was not highly sophisticated.

My feedline is 160 feet of RG58/U, and I intentionally have no breaks (no 
connectors) in this feedline (one solid run of feedline from the connector on 
the back of my preamp to the primary of my transformer which is located at the 
antennas (my feedline is soldered directly to the transformer primary), and I 
did this to eliminate any and all weather related connector problems.  

I only use one transformer to feed my 3 pennants, and I do switch the high 
impedance side of the transformer (the transformer secondary), and I switch 
both ends of the secondary (mandatory for multiple point fed pennant systems).

I have 14 turns of my coax run through 3 stacked 2.4" O.D. 31 mix cores to help 
prevent common mode current, and this choke is located approximately 25 feet 
away from the base of multiple pennant feedpoint.  Also have 14 turns of my 
relay control cable (CAT 5 cable) running through 2 stacked 2.4" O.D. 31 mix 
cores which are located on the ground below my antenna feedpoint.
Don (wd8dsb)

UR RST IS ... ... ..9 QSB QSB - hw? BK

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