From: "Gerry" 
Subject: RE: [drakelist] T-4XB AM question


The 756 band scope was intended to be used as a visual receive indicator I
don't think it was meant to be used as a piece of test instrument such as a
spectrum analyzer. Maybe it can be used as such but I wouldn't rely too
heavily on the results. Maybe the T-4XB overloaded the front end of the
receiver. Yes, I know the 756 front end is bullet proof but there are limits
to everything. Was the T-4XB defective (usually a bad tube or contact
oxidation), was it tuned properly into a dummy load, etc...? Certainly what
you observed is not good but I question the method and the tools used. The
only sure way to find out would be to put it on a test bench with a spectrum
analyzer. Lacking that I would enlist the help of a fellow ham some distance
away to listen to my signal and give me a report as he tuned roughly +/-
20kHz. Maybe he could give you an audio recording of your test transmission.
Forgive my skepticism but strange things can happen when you try and use a
sensitive local receiver to monitor your own signal. For example, my
otherwise fine SPR-4 picks up a loud AC hum while trying to monitor my own
signal without an antenna plugged into it. If I insert an RCA plug with a
short to ground, the hum goes away. That's on HF. For 6 meters I use a
converter ahead of it and I don't have a hum.

73, Gerry W1ID

 -----Original Message-----
From: owner-drakelist{at}www.zerobeat.net
[mailto:owner-drakelist{at}www.zerobeat.net] On Behalf Of John_K7FD
Sent: Monday, November 03, 2003 11:57 PM
To: drakelist{at}zerobeat.net
Subject: [drakelist] T-4XB AM question


Hello,

When I keyed my T-4XB (no modulation) on AM at 3.871 MHz, I took a 'look' at
the signal on my IC-756ProII band scope. What I saw has me a bit concerned:
I see my signal has two smaller carriers on each side -- one at 3.851 MHz
and one at 3.889 MHz. It appears the relative amplitude of the side signals
are about half the strength of the carrier on the intended transmit
frequency...

...has anyone come across this before?

Thanks,

John K7FD

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