Using Meffa

K4QXX

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.

Burch

K5XH

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

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

Dave wo2x

K4QXX

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

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

Piero Ferrua

Good morning colleagues,

I also had the same problem with the MEFFA.

My setup Flex 6600 + 3 elm StepIR (6-40 mt) + PGXL (firmware 3.8.4)

Working TX5S in CW I could not obtain an output power higher than 350W 😣😥despite a 22W or 70W drive.

In all other emission modes or frequencies I did not find such an evident limitation.

Recently under CB0 pileup... by chance I tried to bypass the MEFFA and magically the radiated power increased to 1500W !!!!!🤩

From subsequent checks it is as if by activating the MEFFA, with the same driving, there is a reduction in power emitted on all transmission modes that is decidedly more influential on CW.

The fans also start earlier, but this is due to the extra heat generated by stronger output.

A few days ago I therefore decided to leave the MEFFA inserted for all transmission modes except CW, this for any transmission band.

Kind regards 73 de IZ1XEE Piero

N3PS

I'm a new Flex user and have been running MEFFA . . . however, I have noted behavior where one cycle of FT8 I am below 500w and then a subsequent cycle I have way over . . . I understand that there is a tuning (learning) process, but I found that it seems to forget and them I find I am running more power than I want. Although the amp runs cooler with it on, I'd rather not have an unexpected power increase. I've gone back to turning it off . . .

Mike-VA3MW

What Band? This can happen on 6M.