From: Garey Barrell 
Subject: Re: [drakelist] T-4XB AM question


John -

This is NOT normal operation.  You have a spurious oscillation of some 
sort, most likely caused by a failed electrolytic cap (C129) in the 
transmitter.

Obviously the capacitor is not shorted, just higher than normal ESR. 
So if you tack a temporary electrolytic of similar size across it your 
spurs should disappear.

A secondary, less likely possibility is bad filter caps in the power 
supply, particularly the bias supply.

The 4 Series makes perfectly acceptable AM of the "controlled carrier" 
variety, making it suitable for use with a linear amplifier.

73, Garey - K4OAH
Atlanta

John_K7FD wrote:
> 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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