[UK-CONTEST] [CDXC] Detuning TX antenna on receive.

[Neil G0JHC]

Dave, I assume you are detuning  the antenna at its feed point and not
trying to do it from the shack?

 

 

Here I find the rx antenna within 100ft of the TX antenna  on 160m adds
about 2 points of  "induced" noise if you don't detune at the Antenna base.
Once over 200ft feet away its not needed. 

 

So if your TX/RX ants are 80-90m away .. about 290ft, I say you don't have
to worry too much and won't notice much of a difference if at all.

 

Neil G0JHC

 

From: CDXC at yahoogroups.com [mailto:CDXC at yahoogroups.com] On Behalf Of David
Gould
Sent: 21 February 2010 17:35
To: CDXC at yahoogroups.com; 'UK-Contest'
Subject: [CDXC] Detuning TX antenna on receive.

 

  

I have just put up a K7TJR RX 4-square in preparation for next 
weekend's contest.

The TX Inverted-L is about 80/90m away from the 4-sq.

Following the common held view, and also shown very strongly in EZNEC 
modelling, I have built the facility that the TX antenna is detuned 
on RX.. but out of interest I put in a switch to override the detuning.

After a range of listening tests last night on US (inc west coast) 
and EU stations on the front and off the back I could not detect any 
difference when the TX antenna was resonant or detuned.

Has anyone else done similar tests and noticed any difference? And 
if so what sort of degradation did you notice when the TX antenna was 
*not* detuned?

BTW the K7TJR 4-SQ.. was working brilliantly, I hadn't appreciated 
that it would be so low noise as well as directional, though it 
probably could do with a small preamp to equalise the gain to reduce 
knob twiddling when switching.

73,
Dave, G3UEG

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