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PGXL Questions from a new owner

I just received my PGXL and have hooked it up. I love how well integrated it is with my 6600M. It replaces my Expert 2K-FA + 4O3A 1A2R switch that was used to share the amplifier between the 2 radios. There was a considerable reduction in cabling with this: No more serial port cable between the PC, amplifier and 6600M; no more PTT cables between the 6600M, 1A2R switch and amplifier; and fewer coax cable connections. I also notice some reduction in 2nd harmonic cross-band interference. I love it.

I have a few questions that I'm sure seasoned users can answer:

1) When not using Meffa, what drive level does it take to achieve 1500W output with continuous carrier or 'tune', i.e., what is its gain? It takes a higher drive level than my Expert 2K-FA, which only needs about 33 W.

2) I started to play with Meffa. Power output dropped significantly. I increased the drive in steps up to about 60 W but the power output remained the same, about 750W. Is this normal or am I doing something wrong? Does Meffa limit the power output so much?

3) In the PGXL Windows utility, there is a usage chart. It seems to show a much lower output power than the power meter shows. I am thinking that the power meter shows instantaneous power whilst the usage chart shows power averaged over some time interval that includes the time when transmitting CW character elements as well as all of the silent periods between them. Is this a correct understanding?

4) There seems to be no way to remotely power on/off the PGXL. Is that correct? I'm thinking that I need to leave it on in standby when I go to operate remotely.

5) With my former setup, in the SO2R menu in N1MM, I had to set the radio swap transmit lead time to 400 ms to make sure I'm not hot switching the relays in the 2K-FA and 1A2R switch. Can this be set back to 0 ms?

73, Les VE3NNT


  • bahillen
    bahillen Member ✭✭✭


    i can only answer a couple questions.

    Meffa changes the conditions of the amplifier. You will notice the VDD change. The different operating conditions reduce the gain thus requiring more drive. With Meffa the temperature will drop 10 to 15 degrees. This is normal. Only getting 750 watts is not normal and could be due to SWR or power supply voltage with your flex. Sound like fold back.

    you can’t power off the PGXL remotely without a internet switch which is a good idea for other reasons. Some have a number of things they want to control remotely.

    I have my tx delay at 20 ms.

    You may want to try your testing on all of your bands and compare PO. Things to note are your Id, PO, driver PO, Vdd and where your PO starts to limit. If you I’d gets over 50amps it may cut back.

    There are filter in the amp and could be tuned a little differently or the antenna reactance/impedance impact your amp.


    Bill W9JJB

  • KM4CQG
    KM4CQG Member ✭✭

    Hi Les

    On Phone with Meffa on 45 watts in gets me Peaks to 1500 watts. This is on 20M with a Hex Beam SWR 1.10.

    With 10 watts on FT8 Meffa I typically get about 235 watts. Hex beam same SWR 1.10

    Amp runs less power with Meffa on but there plenty of breathing room.

    My voltage input to PGXL is 240.


  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    Hi Les

    • You really can't compare drive power between amplifiers. Keep in mind that in the US, Amps are limited to a maximum of 15db gain. So, to make sure we make full power out (non-MEffA) we need to adjust the driver power accordingly.
    • With MeFFa, you will require more drive power and this will vary based on the modulation scheme you are using since the PGXL will actually determine that. More drive power will be required with MeFFa on as the bias changes. This results in a cooler running amplifier and it may take 2-4 transmissions to get it adjusted to your liking. Again, keep in mind the max gain legally allowed (in the US by the FCC). MEffA is a bit fussier on 6M, and we are aware of that. We continue to work on improving that.
    • The Usage Chart is something we are still working on improving, so you might see some strangeness with it
    • In Standby, we only have a small 24v power supply running and the PIC power controller, so it doesn't consume much power. For me, in long term remote, I have a 240vac relay that I use to turn off power for storms (home brew)
    • About 20ms is good enough for the TGXL in TX Delay for the PGXL.

    The PGXL is very very robust. I have overdriven it more than once or even had a badly tuned Steppir on 6m and it does a great job of taking care of itself. Right now, the best SWR I get on 6M is about 1.9:1 and the PGXL (no tuner) handles that wonderfully at full Canada digital power.


  • Les Brown
    Les Brown Member ✭✭

    Thanks for all the feedback guys.

    1) My Expert 2K-FA is an international version that has a higher gain than 15 dB, so that explains the difference.

    2) I did some further testing with Meffa and it seems that I was doing something ****, adjusting the tune power but then keying with the paddle, so I wasn't actually changing my TX power. After sorting that out, Meffa seems to work fine. I documented the Vdd and Id with different drive levels on different bands. Generally, with Meffa, I see a lower Vdd for a given output power than without Meffa. I haven't used the amp enough to see how the internal temperatures differ with and without Meffa for a given output power, but given the comments, I think I should leave Meffa enabled to try to keep the temperature down.

    3) On the usage chart in the PGXL utility, thanks for the feedback Mike. I'll ignore the chart for now.

    4) I use an internet power switch to turn power on/off all of my 120 volt equipment. I don't have a switch for 240 volts. I'll look around to see if I can find one. With my Expert 2K-FA, it would power down when I turned off the radio, so I didn't need an AC power switch, although maybe it is a good idea for lightning protection.

    5) I'll set my TX delay to 20 ms as Mike suggested in anticipation of acquiring a TGXL later this year. I guess I can set the radio swap transmit lead time in N1MM back to zero without worrying about hot switching if the timing is all controlled by the radio and amp.

    73, Les VE3NNT

  • W9WLX_Chuck
    W9WLX_Chuck Member ✭✭

    Keep in mind that MEffA is not available in class AAB mode. MEffA does not work with signals with varying amplitudes, such as SSB, AM, or phase-shift keying digital modes like PSK-31. These modulation modes require more linear operation (class AAB). Though the MEffA indicator may be on, it is only operational in class AB operation and does not affect class AAB operation. Pg 45 PGXL User Guide.

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