TX power does not reflect adjusted power level.

K7GFH · September 5

Hello,

Posting this to the Mac forum as this is the flavor I run on my Flex 6400. I realize this may be a hardware issue. Per the attached screen shot, I am unable to see TX power on FT8 near my set power limit. In this case, 40 watts. I also have the same issue when tuning up. As the screen shot shows, my tune up power is set to 15 watts but I usually only see 1-3 watts per the meter. I am able to make contacts. Every now and then, the TX power will get close to the adjusted power level but not often. I have removed power from the 6400 multiple times, reboots etc., with no immediate change. Am I missing an ALC adjustment here, maybe this is normal? Appreciate any insight.

Jay (K7GFH)

K3CDY · September 5

Just curious, have you tried using WSJT-X versus the built-in FT-8 tool? In WSJT-X, you can adjust the output level. It would be interesting to see if you get any better results.

If you do, then I would suspect a software issue with MacSSDR, and reaching out to Marcus would be appropriate.

Mike-VA3MW · September 5

ALC won't have anything to do with this.

Let's start by making this simple.

What power do you see when using the TUNE slider at 100%? You should see 100 watts into a dummy load or close to it. If you don't then, the supply voltage at the radio is the next thing to look at and it needs to be close to 13.0V if at all possible.

The TUNE exercise tells us where to look next. Let us know..

73

K7GFH · 3:00AM

"Just curious, have you tried using WSJT-X versus the built-in FT-8 tool? In WSJT-X, you can adjust the output level. It would be interesting to see if you get any better results.

If you do, then I would suspect a software issue with MacSSDR, and reaching out to Marcus would be appropriate."

Thanks Bill. I have not tried WSJT-X outside of Mac SSDR. I was about too today then tried a few more ideas. The easiest to explain is in AM mode. When requesting 50W of power, the AM carrier is roughly 3 watts. Same with the tune function, requested 15 watts, actual is 3 watts as well. I figure if these simple settings are not functioning properly, digital will not as well. I believe I am leaning towards a hardware issue at this point. I do have an open ticket with Flex and fortunately, the 6400 was a recent purchase from Flex so hoping for warranty support if a problem is found.

K7GFH · 3:08AM

ALC won't have anything to do with this.

Let's start by making this simple.

What power do you see when using the TUNE slider at 100%? You should see 100 watts into a dummy load or close to it. If you don't then, the supply voltage at the radio is the next thing to look at and it needs to be close to 13.0V if at all possible.

The TUNE exercise tells us where to look next. Let us know.."

Thanks Mike. I am at roughly 13.14 volts when tuning at 100W. Requesting 100 watts yields roughly 20 watts. Requesting 15 watts yields roughly 3 watts. See attached screen shots showing both.

Jay

KD0RC · 3:23AM

Hi Jay, can you adjust your power supply up so that you are showing closer to 14 volts when transmitting? (I think that is what Mike was trying to say, not 13 V).

K7GFH · 3:40AM

I can do that Len. Will bump it closer to 14 volts and give it a try. Thank you!

Jay

K7GFH · 5:13AM

Hello,

Here are two screen shots. 1st with 14.26 volts to Flex, no TX. 2nd shows voltage drop to 13.73 volts with TX, tune at 100 watts.

Screenshot 2025-09-06 at 10.11.40 PM.png

Screenshot 2025-09-06 at 10.11.01 PM.png

Thanks!

Jay

Mike-VA3MW · 1:15PM

@K7GFH If you can't get close to 100% with 100% tune and more than 13VDC, it is likely an issue with the radio. Tim and the guys will get you sorted out.

Support has been a bit busy, but they will get back to you.

K7GFH · 2:54PM

Thank you Mike.

Jay

TX power does not reflect adjusted power level.

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