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Re: LF: G0MRF-TX-ouput circuit troubles

To: [email protected]
Subject: Re: LF: G0MRF-TX-ouput circuit troubles
From: [email protected]
Date: Wed, 26 May 2004 08:39:19 EDT
Reply-to: [email protected]
Sender: [email protected]
In a message dated 25/05/2004 22:01:42 Central Europe Standard Time, [email protected] writes:

Maybe somebody has something to say about this......

I think you're spending too much time measuring things at frequencies that are not LF. It's a great analysis of the detail, but I can't help thinking you are overlooking an obvious fault.
BTW.  What is the output power? The supply Voltage? and the efficiency?
Just concentrate on the basics. The circuit works, but if you start removing diodes adding resistors etc, then there's not much anyone can do to help as you are now developing your own circuit and not trying to duplicate mine.
Build the circuit as close to the original as you can.
Check you have the correct waveforms at the gates. (keep wire lengths short. This maybe 136kHz, but the waveform rise and fall time neeed to be fast. Around the HEF4013, FET driver and FETs, the construction should be consistent with good VHF practice ) 
Measure the 136kHz output power, the supply voltage and calculate efficiency.
Then you'll have a benchmark of performance. If you have less than 200W output from a 36V supply or an efficiency less than 60% then you have a fault in a component or in the construction that you need to find.
After you have a reasonable benchmark, change one thing at a time and compare. If you have an improvement, leave it in circuit. If you don't, then put it back as before and try something else. Jim's work on the transformer is excellent and I'm now comparing my original transformer with a version of Jim's built on a 3C90 42mm core as supplied in the kit.
I've built versions of this circuit from 400W at 73k to 700W (4 FETs) at 136kHz. There's even a version running in the Medium waveband around 1200kHz.
Good luck
David   G0MRF
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