Greg,
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 scale).
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@tin.it To: "Steve Raas" sraas@optonline.net, "AMSAT-BB" amsat-bb@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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