[TowerTalk] Elementary Rx protection question

[Al Kozakiewicz]

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 at 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
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