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Re: [TowerTalk] Elementary Rx protection question

To: Pete Smith N4ZR <n4zr@contesting.com>, TowerTalk <TowerTalk@contesting.com>
Subject: Re: [TowerTalk] Elementary Rx protection question
From: Al Kozakiewicz <akozak@hourglass.com>
Date: Sun, 13 Jan 2013 19:06:40 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
I built a K9AY loop that uses a mini-circuits 9:1 DIP matching transformer.  
When first constructed, I blew out several of them whenever I operated QRO.  
Being unsatisfied with the performance of the transformers I wound myself on 
binocular cores with relatively heavy wire (I know now what I was doing wrong) 
I slapped a couple of Si signal diodes across the primary winding of the mini 
circuits device in desperation.  It worked.  I do not notice anything odd about 
the Rx performance.  In fact, the antenna has wonderful S/N on bands even where 
it is no longer directional (40m and 30m) compared to the vertical transmit 
antenna.

Al
AB2ZY

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Pete 
Smith N4ZR
Sent: Sunday, January 13, 2013 3:58 PM
To: TowerTalk
Subject: [TowerTalk] Elementary Rx protection question

Do back-to-back diodes across a receiving antenna degrade receiver performance 
before they begin to conduct?  what I'm considering is back-to-back series 
strings of diodes to limit RF voltage at the front end of an SDR.  My working 
assumption is that the conduction threshold could be set below the damage level 
but above the ADC clipping level, but if it affects performance before the ADC 
clips then that's no good.

-- 

73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.

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