After rewinding L401, swapping C516 and C525 to the correct values, updating firmware to v1.03, and doing a factory reset, the RF Sweep plots look MUCH better and are fine for all bands. Band configuration looks correct in Putty.?

But the power is low, less than 1 watt on 40, 30, and 20 meters. It’s about 4 watts on 80 and 60 meters. Transmit bias is set to 30 for all bands.

The fact that 60 is good and 40 is much lower led me to troubleshoot the signals around their shared LPF. The voltages for the LPF Enables to Q509/Q510/Q511 all seem to change correctly to select which LPF is in use. The PIN diode voltages for the 40/60m LPF do not change between 40 and 60m, so it looks like the same LPF is being used for both, as expected.?

What are recommendations for discerning why 40m is much lower output than 60m, if both have been verified by both Band Configuration and PIN diode voltage measurement to be using the same LPF? ?What should I look for now? ?I have verified continuity through all the LPF toroids.?

I do have a Nano VNA, and can probably get my old O’scope working if I knew what to check. Thanks in advance for any help.?

Walt - KK4DF

I tested my LPF sections with a Nano VNA, and all the frequency plots look good to me.? In fact, the 40m LPF looks to be right at the bottom of the 40m band, but the power output on 60m is 4.5 watts and 40m is 0.6 watts.? I hope someone can lead me in the right direction as to what to check next.






Thanks,

Walt - KK4DF

Jeff,

The capacitor values were swapped in an early version of the assembly manual.? If you built from a more recent version of the manual, no need to correct.?

Walt

Jeff,

IIRC, Hans said it didn't matter much.
His mod page says "swapping the capacitors to correct this mistake (which?I have done, and is implied in the analysis below) does NOT materially improve the receive band pass filter response on 20m".

I have not swapped them yet and I'm getting 3.5W out on 20m.

73, Mike KK7ER

Worth remembering the PA output is unlikely to be 50 ohms? so a VNA check is useful but don't sweat the details if you're getting plenty of power through it . .? ? ?If not play with the windings?

Bruce,

I played with the windings, especially for the 30/20 LPF.? I saw absolutely NO CHANGE in the power output, whether compressed or separated.? 20m power output is only about 0.25 watts.? I've also carefully recounted turns on all toroidal.

Walt

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Walt,

Cliff,

I agree the problem may be a solder joint, but since 60m has great output and 40m is much lower, there seems to be something more. Also, I've tested continuity through all the LPFs, and all seems good.? Plus if the toroid joints were bad, I think the Nano VNA plots would have shown a problem.?

I'm suspecting something around L502 or T501 may be keeping the amplifiers from properly operating as Class E on the higher bands, or something like that. I will likely do some test with an O'scope later this week.

Walt