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Re: LF: G0MRF transmitter problems

To: [email protected]
Subject: Re: LF: G0MRF transmitter problems
From: "Marek SQ5BPM" <[email protected]>
Date: Tue, 11 May 2004 21:01:15 -0000
Reply-to: [email protected]
Sender: [email protected]
Hello Dick and all,

Hello all,

well I rewound the ouput transformer.
Again I have problems, and when checking the signal on
a spectrum analyzer I found that it is peaking on the second harmonic.
So it transmits the main signal on 272kHz.........
136kHz is also present at the ouput, but much much weaker.

It really makes me puzzling.

Dick, pa4vhf
You're lucky to owe a spectrum analyzer! It would have saved me a lot of
time in some projects...

However, if you have an oscilloscope as well, check the waveform on FETs,
should be fairly close to a square wave. Heavy ringing can pull the output
waveform almost to zero after the initial peak, thus making the double
frequency (at least this happened to me). Check also for possible coupling
of the ouput stage with CMOS driver. What helped in my case was a solution
by G3YXM (thank you!) : a capacitor around 1nF in series with around 22 ohms
resistor, both connected in parallel to the primary winding of the
transformer (marked as Z on the schematic here
http://www.wireless.org.uk/136bigtx2.gif ).

I am still trying to get some motivation for finishing the RX loop...

73! Marek SQ5BPM



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