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Strange PGXL noise behavior

Hi all,

So it has been a busy week and I didn't do much if any hamming until today. I connected to my Flex and immediately saw some awful noise on 40m that I know is related to my 24V linear supply that is fairly near the radio. I unplugged that and the noise went away as expected.

I tuned on 40m, PGXL offline and 40m looked good. My HF Auto tuned the CW band to 1:1. Bypassed it is 1.5:1.

I switched to 20m and saw this:

Basically S7 noise across the band! So I tuned again on 20m and the HF Auto brought the SWR down to 1.2:1. But still the noise was present. I bypassed the tuner and the SWR was 1.5:1 so I think antennas were working right.

Switched back to 40m and tuned. No issue. Switched to 30m and tuned. No issue. Bands and noise there looked normal.

Back to 20m and tuned, still S7. So I put the PGXL online and tuned again with about 400 watts going out. The tuner was still happy. PGXL seemed happy. After stopping tune the noise was back down to my normal S3:

So what about putting the PGXL online on this band changed the noise produced?

Anyone have any idea?


  • Bill NE1B
    Bill NE1B Member ✭✭✭

    I would say nothing to do with PGXL. I see the same noise on 20 thru 10m., intermittently from a local power line insulator arcing over. Power company will eventually replace it.

  • Mark_WS7M
    Mark_WS7M Member ✭✭✭

    Hi Bill, but then how to you explain that it went away AFTER I put power out from the PGXL?

  • Mark_WS7M
    Mark_WS7M Member ✭✭✭

    Also our power in this neighborhood is underground.

  • Bill NE1B
    Bill NE1B Member ✭✭✭

    Does the noise go away when you put PGXL in Standby? Or if you turn the power switch off?

  • Mark_WS7M
    Mark_WS7M Member ✭✭✭

    Hi Bill...

    So to be clear:

    Fired up SmartSDR. Noise was present across 20m.

    Tuned using tune button on 20m. This causes my HF Auto to tune my 80m loop for 20m. This was all happy. SWR came way down to like 1.2:1. Without the tuner it is 1.5:1 typical.

    Noise was still present after tuning. Switched to 40m and tuned there. That band looks ok except for power supply noise from a known source. But tuner and ant were happy after tuning at 1.3 or so SWR.

    Back to 20m. Noise still wide across the band at like S7. A local buddy tuned in and got S2 on his radio across town.

    Tuned again on 20m. Same deal. Noise still there but all parts of my system seemed happy. Still S7 noise. I could see some CW signals on the band so I knew I was receiving ok.

    In the past when I had a 6500 I had one of the protection diodes **** on Ant1 and it looked sort of the same but was noise on ALL bands not just one.

    I put the PGXL in operate mode, raised my tune power to about 30 watts and hit tune. The PGXL showed an output of about 400 watts and the SWR was good. I released tune and suddenly the S7 wide noise on 20m was completely gone and signal was down around S2-3 across the band.

    Now there is a possibility of some line noise that just coincidentally went away at the exact same time I transmitted on 20m using the PGXL but in watching the TX pan I don't think that was the case.

    While transmitting with the PGXL on the SmartSDR pan changed as if the signal path had some how changed. I used to see this when a balun I was using would begin to heat. Over time the shape of the TX wave form would change. But this was almost instant. Way to fast to capture and actually it was that change that caused me to stop transmitting. And then the noise was gone.

    My suspicion is something to do with the band pass filters in the PGXL. Some thing was "clicked in" that should not have been and it took a transmit cycle on 20m to clear it.

    Come to think of it, it may have cleared on a PGXL transmit cycle on any band actually. I never transmitted with it on 40m so that might have fixed it too.


  • James Charlton
    James Charlton Member ✭✭

    Maybe there is a loose or corroded connection somewhere in the RF line between the transceiver and antenna. When you ran some power you burned through and established a good, noise free, although temporary, connection.

    With no further info, that's my shot in the dark,

    Jim AD0AB

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