TX power spikes

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  • Problem
  • Updated 5 years ago
  • In Progress

When transmitting on SSB, I see regular power output spikes well in excess of the RF power level setting.

For example, I set the RF Power slider to a value of 45.  I also set the TUNE slider to a value of 45.  If I press the TUNE button, I measure a carrier power of approx. 45w.  Likewise, if I produce a steady tone into the microphone, I also measure a steady power of approx. 45w.  

When talking into the microphone, obviously my average talk power will be down some, but in addition to seeing the normal peaks of approx. 45w, give or take, I am regularly seeing SPIKES of power upwards of 60-70w.  Maybe every 20 words or so, I will see the spike in transmitted power. 

If I set the RF Power slider to another value, I still see spikes in excess of the desired level setting, whether it is set for 25w or 75w. The spikes appear to be approx. 40% higher than the set level. For example, if I am set for 25w, I will see spikes to 35w. If I am set for 70w, I will see spikes close to 100w.

I am measuring this on two LP-100A meters. One coupled to the input of my amplifier, and one coupled to the output.    While watching both meters, I normally see 40w into the amp for 1500w output. However, when I see the spikes, the input will hit peaks of 60-70w, and correspondingly the amplifier will spike to 2000w or so.   Not good for expensive tubes, nor remaining within legal limits.

When I initially called Flex to reported the issue, it was recommended to try running the compressor. I have tried operating with the compressor enabled, which has made no difference in the issue.  My mic gain and audio input levels are adjusted so that my extreme voice peaks are just reaching the 0DBM point, and average voice levels are at the "L" of the word LEVEL.

The issue is occurring on all bands. 80,40,20,15m tested so far. It occurs regardless of whether the TX equalizer is enabled or disabled. Likewise, I can enable or disable my external audio processor (Symetrix 628), with the same results.

This appears to be quite similar to the old ALC issue that plagued the 5000 for a long time until the corrections were made in PowerSDR.



Photo of K2CB Eric Dobrowansky

K2CB Eric Dobrowansky

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Posted 5 years ago

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Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

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Official Response
I have converted this topic to a support HelpDesk ticket (http://helpdesk.flexradio.com) for expedited issue resolution.  If anyone else is experiencing an issue similar to this one, please submit a HelpDesk support ticket for issue resolution.