[AMRadio] When talking about AM power

Geoff ars.w5omr at gmail.com
Sat Oct 10 05:49:09 EDT 2015

On 10/09/2015 08:01 PM, b.gaz at comcast.net wrote:
> I have and use a scope off the receiver IF, 

The problem with that is, the IF gets saturated and the AGC of the
receiver doesn't respond accurately.

Let's say you're running a transmitter like John/WA5BXO built up, that
has enough audio power in the modulator to properly modulate his carrier
with his peak'ed asymmetrical voice.  If you try to monitor that signal
in the IF of a receiver, you'll never see the positive peaks of the
signal, until you turn off the AGC and reduce the RF Gain to the point
where the signal is not overloading the front end of the receiver.

Best thing to do for a monitor scope is to take some small coax and feed
it into the scope's BNC or banana-jack input, and run the other end
outside near the antenna.  5 or 6 turns and a couple of inches diameter
(nothing is exact) of some stiff copper wire connected to the coax and
supported somewhere will give a much truer reading of what your
transmitter is producing.  Monitor transmitted signals, not those that
are passed through multiple stages in a receiver.

> and an sdr spectrum display. 

Now, that's something I'd like to get into, as well.  The spectrum
display on an SDR device.

SDR intrigues me.  I've played with a couple of on-line SDR receivers
and seeing the actual bandwidth of some stations is amazing.  Having a
receiver with no other noise and only monitoring the transmitted audio
would tell a lot about some other components of the transmitted signal.

73 = Best Regards,

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