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Using Meffa

I didn't want to put in a helpdesk ticket for this as it's just a question. I like using Meffa mode on the PGXL because the temps stay down and the fans don't kick in as much. I only use Meffa mode when I am running FT8 and I rarely run more than 500 watts. Once I started using Meffa, I had an issue with the amp where it would take a lot of drive to get output and I couldn't get the amp over about 800 watts. Sent to flex and they fixed and sent back. About 2 months later, had the same problem. Sent to flex and they fixed the problem. Since then, I have stopped using Meffa. No problems with output and works great. However, I really like using the Meffa mode on FT8 because of the lower temps and less fan noise. I am scared to use Meffa mode now because of the issues I have had before with the amp. I am assuming my issues had nothing to do with using Meffa mode but I am now gun shy.

Tonight I was working 6 meter FT8 working into South America. The amp seems to get hot and fans run high when running about 400 watts on 6 meters FT8. Turned on Meffa and output (with same drive) went down to about 320 watts (which I expected) and the amp started running much cooler and fans were low.

I guess this is a question to Flex but should I keep using Meffa on FT8? I surely don't want to mess up my amp again but I like when it runs cooler and more efficient.



  • K5XH
    K5XH Member ✭✭

    Hi Burch,

    I have noticed the same thing during a recent RTTY contest. I had preset the power levels from the 6600 to provide ~1000 watts on the 80 - 10M bands before the contest. I found that I had to increase the 6600 output to get back to the original level. At one point (on 80M) I had the 6600 set to 85% in order to obtain just 800 W output. I doubt that I could have gotten full legal power out of the amp even if I had wanted it. I also noticed that the Vdd reading on the amp's display would vary between about 30 volts and a bit above 50 volts. I wish I had kept notes on all this but I didn't. After the contest was over I started to think about this issue and thought that Meffa might have had something to do with it. I never thought to turn it off during the contest. I will do some further testing this weekend.

    73, Mark K5XH

  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator

    It is recommended to leave MeFFa off on 6 and 160. The new 3.7.28 firmware does this.

    Dave wo2x

  • K4QXX
    K4QXX Member ✭✭

    I understand that using Meffa will take more drive to get power out but I just don't want to damage the amp. When I started using Meffa a lot, that's when I had problems with the amp. I have left if off since the last repair and no more issues. I guess I will just leave it off and not worry about the higher temps/fan speed.

  • W9WLX_Chuck
    W9WLX_Chuck Member ✭✭
    edited February 19

    Dave, one detail I'm noticing is that the MEffA indicator on the PGXL indicates that MEffA is on when the radio is in DIGU mode on 6 or 160. However, on the PGXL utility it correctly displays that MEffa is off when the radio is on 6 or 160 in DIGU mode. MEffA is enabled in the utility and the behavior is the same on CW. PGXL is at 3.7.28 with a 6600 at 3.4.21 and there is a TGXL in line at 1.1.16.

    Chuck W9WLX

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