SSB AVERAGE POWER

Steve K8DZ

I notice that the average power on SSB is not as high as some other radios (given same CW or Tune power of about 100W.) Processor on 6700 is DX+ and hitting audio right up to red. Equivalent frequency responses on all radios compared.  Power SDR had this same issue for a while (I had a 5000 and still have a 3000). It was 'fixed' when the LEVELER function was added.  Any possibilities of a similar idea for SSDR ?

Charles - K5UA

Noticed the same thing on my 6500. Have to run the mic gain almost into the "RED IS DEAD" zone to get anywhere near the power output on a peak reading wattmeter, or to drive an amp to the same power output that registers when CW is used to drive the same amp. As an example, I set the power level control to 30 watts on CW and the PEP wattmeter reads 30 watts. Change to SSB and the PEP meter only reads 15 -17 watts when I'm banging up against the last yellow bar before the red bar. Interestingly, when I use a second radio and set it for 30 watts in CW, switching to SSB still reads 30 watts PEP. When driving the amp for the same indicated SSB power level on the two transceivers, the second radio drives the amp way past the output power than the Flex. Very, very perplexing. Would make a good video for the non-believers.

Mike - N8MSA

I have only begun looking at this, as I'm usually playing with receivers, but I have noticed a 'sag' after the beginning of an SSB transmission similar to "pre-leveler" PSDR behavior. This apparent on sampling vector wattmeters, oscilloscopes and even (though to a lesser extent) on receivers, though AGCs tend to mask the audio effects. One thing that I've noticed is that any kind of 'start-of-transmission noise', such as PTT switch closing loudly, seems to drive the output down immediately after several hundred milliseconds of expected output.

I don't have a D'Arsonval wattmeter, but I suspect it's very apparent even on them. What kind of meters are you using?

I am, as mentioned, just beginning to look into this so I don't have a lot of hard data yet but this behavior is noticeable and reproducible. Any comment from Flex?

73,

Mike - N8MSA

Steve K8DZ

I am observing what I called average power on a Bird 43 wattmeter. This is with CW and tune power set to same as other radios.  I will check this out further with my peak reading wattmeters and see if peak is down as well.  My amp only needs about 60W so what I have been doing is setting the tune power at max the amp can take (limited by screen current) and then on SSB, advancing the RF Power slider to maybe 10 points higher than tune power. It shouldn't work this way but it is a workaround. Would be a problem if I needed 100W.  I will look into this more later today or tomorrow.   73  Steve  K8DZ

Tim - W4TME

Power output on SSB needs to be measured with a true peak reading power meter in to dummy load for greatest accuracy.  The mic also needs to be set up properly where you are peaking the level just "tickling" the red for full modulation.

Mike - N8MSA

Tim - 

I'm doing exactly that - I'm using a Telepost LP100A and an oscilloscope, into a dummy load and at a variety of input levels including "just tickling the red" - and I'm seeing a 'flare' to the desired power, followed by a sag.

Charles - K5UA

Tim, Just read the CESSB article in Feb QST. Very interesting graphs showing the reduction of overshoot. Has Flex actually verified this by using random voices thru the Flex CESSB and looking at the output on a scope as presented in the CESSB article. I ask this because my audio has been criticized for distortion that sounds a lot like overshoot. Have heard it in recordings of my audio emailed to me by friends that I trust. Also see this effect on my PEP Array Solutions wattmeter when I drive my amp with the Flex. Even "tickling the red" doesn't seem to drive the amp as other radios do at the same exciter output power. Wondering if I have a hardware problem? The Flex on CW drives the amp beautifully.

Tim - W4TME

I am looking into this.  Thanks for bringing it to our attention.

Steve K8DZ

I took some more detailed measurements with three wattmeters (LP-100A, Acom amp peak reading, and a Bird 43) into a 50 Ohm Bird 30 dB 2000W attenuator. Output of attenuator to o'scope. SWR 1:1.  I tested three different radios  including my 6700 with same tune power on 10M. Set all 3 radios for 50W out Tune power and set the 6700 RF Power to same as Tune power. Result : All three radios showed 50W peak power on SSB on both peak reading meters and scope showed same peaks as tune on all radios. There was no overshoot that I could see on a 60 MHz scope from the 6700 and peaks were right where they should be. Then looking at the Bird 43 to get a rough feeling of average power, all radios at optimum compression, two other brand radios showed around 20W average while speaking. The 6700 only read about 6W. The difference was very obvious on the scope as well. The DX+ was used. Mic gain was set to just occasional hit the red . Audio response of all 3 radios has been carefully EQ'd to sound the same.  I can provide more info to FRS engineering if requested. 

End of comments on this for now.  Steve

Bill -VA3WTB

Interesting though, any of the Flexes I hear on the air never seem weak as long as the audio is set up properly.