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So, I am still tracking down the 20W amp oscillation, and making progress. I have C24 in the amp, although it makes no difference to the oscillation in the high bands. I also have the onboard

I will be home tomorrow evening late and will have a closer look. It is not likely that it is the PA itself. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator

A picture of the PA might help. I wonder if he fitted C24 ???? Have no idea if this would stop oscillation but worth a check. glenn vk3pe

Sorry no glasses reply this AM Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand

Sounds like the inpuu connection to the PA is high impedance (like something is not connected on the boads in front of the PA).. you migjt take the BpF put of the circuit temporarily. Just jumper

*** Does your RF board have the built-in xmit attenuator? If so, will 6dB there stop the oscillation? I would look for RF on - the power lead and also the control lead - that enables the PA. It might

Thanks Jerry and Bill. I’ll get back to this on Monday. 3 dB pad on input of PA reduces oscillation, 6 dB pad stops the oscillation dave

Remove the bpf and see what happens. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa

I wonder if it will oscillate if you stick an attenuator pad between the BPF and the amp? - Jerry, KF6VB

*** I did get oscillation from my system a few weeks ago. I had installed an End Fed Half Wave antenna. It only happened with my big linear. A big fat common mode choke fixed it. - Jerry, KF6VB

Yes, I agree. The amp is solid. Previously , I swept the amps and got solid performance. And, when I disconnect the drive to the amp the oscillation stops. It is being caused by something in the T41

*** I have to agree with Bill. I built two of them, and neither of them showed any instability. I would try improving the bypassing on the power traces. Scope them to see if there's RF on them. -

Something is wrong. The amp will NOT oscillate by itself. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner

Yes it is on a DL

Do you have it on a dummy load? - jerry

It is the K9HZ 20W amp [email protected]> wrote:

Is it a K9HZ final? Or the one with the IRF510s? - Jerry, KF6VB

I got the second T41 v12 with SW ver66.4 with amplifier operating today.? Both are acting the same, oscillations around 40MHz at several watts when PTT is engaged.? With the oscillation, I was still

I have been setting TX IQ Calibration parameters.? Everything aligns well on the lower bands.? When I engage PTT on 12m, 10m, and 6m in the TX IQ Cal menu, the amp oscillates around 40MHz and draws

Perfect! Or not so much, but its fixed now! Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator