The dummy load arrived and I was able to start some testing with it. The full configuration is radio to amp to RM Italy 27/586 500 watt low pass filter (LPF) to a Daiwa CN-901HP meter to antenna. The antenna showed a starting SWR of flat on channel 1 and 20 and maybe 1.2:1 on channel 40. I used multiple sets of brand new RG8X patch cables 2, 3 and 6 feet long.
Test a) To start out I just tested the setup as it was by connecting the dummy load to the output of the Daiwa CN-901HP meter in place of the antenna coax and tried the Anytone on 4 watts DK, 30 watts PEP on both low and high settings on both AM and SSB. None of this caused the radio to throw a fit and keep the amp latched and the radio's S-meter pegged after releasing the PTT button. I did notice that the SWR would still show about 1.2 on the radio with the dummy load. So maybe it is the antenna or the coax to the antenna or the lightning arrestor i.e. the part of the system I removed....
Test b) Next I connected the antenna coax directly to the amp instead of going through the LPF and Daiwa meter. I tested AM and SSB both low and high on channel 40 since it had the highest starting SWR of 1.2. I did notice that the SWR meter on the Anytone would bounce around a bit between 1.2 and 1.4 but the main problem did not occur. Hmm, maybe it's not the coax or the antenna or the lightning arrestor but the LPF or Daiwa... Not sure if this minor bouncing of the SWR indicates an outdoor problem or if it's a byproduct of our current weather... which is freezing rain, sleet and snow all at the same time. Another special day in NE Wisconsin.
Test c) For the next test I had the amp output into the LPF and then from the LPF to the antenna coax. Basically the only thing not inline was the Daiwa meter. I noticed when transmitting on high the SRF meter on the Anytone would sometime jump over 2 and I think every time I unkeyed the mic, the SRF meter stayed pegged and the amp latched until I turned either it or the radio off.
Test d) I basically just repeated test b) and did find that when bypassing the LPF, the SWR would go up a tiny bit when transmitting on high but it did not cause the signal when unkeying or keeping the amp latched.
The LPF was the only piece of equipment I found in my setup that would reliably cause the problem to happen with the amp on high.
Once the weather conditions are safer outside I think I will take the antenna down and see if I can get the SWR better on channel 40. In the meantime, I will run without the LPF and see how it goes.
I still need to repair the SSB modulation on the Anytone and set the bias for the new IRF520s and hope to be able to try the latter by Wednesday or so.
The LPF filter I have been using is shown below. I just remember when I was a kid I was not even allowed to use my stock 23 channel Royce CB during the evening because it caused so much RFI on on parents' TV, mainly on channels 2, 4, 7 i.e. CBS, NBC and ABC. This made me very self-conscious about doing what I can to limit impacting my neighbors. Except for one in particular that I think swiped two of my rakes.
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