[amsat-bb] Re: Pre amp question

Edward R. Cole al7eb at acsalaska.net
Thu Dec 14 01:01:23 PST 2006


Yes, you can do it by reducing the RF gain to minimum which generally opens
the AGC to max gain.  Since the noise floor is not a large signal, it will
not drive the AGC very much this way.  Note, do not use your s-meter for
these readings.  Connect a good audio voltmeter (ideally with a good analog

Another approach is to use a step attenuator in front of the receiver:
You set you reference on cold sky the same, then point at horizon and
adjust attenuation until the audio meter reads the same reading as cold
sky.  The amount of attenuation in dB give the result.  AGC does not affect
this method.

73's Ed - KL7UW

At 07:48 PM 12/13/2006 -0800, Greg D. wrote:
>Is this test useful on a receiver where the AGC cannot be turned off?  My 
>FT-736 has only fast/medium/slow.  No off.  I would expect a reduction in 
>accuracy, but is it even worth doing?
>Greg  KO6TH
>----Original Message Follows----
>From: "i8cvs" <domenico.i8cvs at tin.it>
>To: "Steve Raas" <sraas at optonline.net>, "AMSAT-BB" <amsat-bb at amsat.org>
>Subject: [amsat-bb] Re: Pre amp question
>Date: Wed, 13 Dec 2006 20:55:50 +0100
>Hi Steve, N2JDQ
>If your receiver has the capability to switch OFF the AGC than the following
>simple test will tell you if your preamplifier connected to the actual
>antenna is working or not for you:
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