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I have a TinySA, NanoVNA, 50MHz scope, DVM's, Taidacent Pwr Mtr, KiwiSDR, audio generators, assorted dummy loads, attenuators, and couplers. I used the NanoVNA to sweep the 20 wt Power Amp (I built 2

Bill, What about bypassing the driver? Can you share what the input power requirement would be after it, and/or how to do so? Can one basically bypass it and connect C1 to the input of T2, or is there

First off… what sort of test equipment do you have Dave? Just stuff like DVMs or do you have something like a VNA or a Spectrum Analyzer? And possibly a signal generator or another radio you can

It could also mean one of your SMA connectors is not making good contact…. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ Owner - Operator Big Signal Ranch –

It means either the relay is bad, you have a bad solder joint on the daughter board, or the sockets/ pins are not meshing to form good contact. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ

I replaced the TX/RX Switch with copper clad perf board and the oscillation disappeared (see pix) . What does that indicate? dave [image: TX_RX Switch Substitute.JPG] [email protected]> wrote:

Along with my front panel design project [which turned out to be the whole case] I have a set of knobs that include dual concentric, small and large sized for the T41 front panel.? There are

Yes that is because the bias is shut off when the PTT is zero volts… on above 3V. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch –

Some further information - with the SWR tx out of the circuit the oscillations continue. When I remove the Tx/Rx switch the oscillations go away. [email protected]> wrote:

I get back tonight. Ill have some simple tests cooked up to get to the bottom of this. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch –

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