SSB power

The power output level of todays DSP radios, is to some extent questionable. A 100watt radio should be able to deliver a 100watt ssb signal, but as things turn out, the ssb power signal registered upon the tx power meter, is apparantly subjected to the modulation depth of the carrier signal.

A 60% modulation depth on a 100 watt CW power output, will give around a 75 watts ssb signal, and a 200watt cw power output, gives some 140watts output on ssb.

Acccording to "F.R.Connor" book of Modulation, 

ssb o/p = [ (m^2 * ssb o/p watts)/4 ] * scale

where m = modulation depth

scale = designed tx power of radio

The scale is a bit of a fudge, but in Connors book, the scale is the AM modulation transmitter output.

Now for the sums, and re-arranging the equation as so:

[ 4 * ssb o/p ] = [ scale * m^2 ]

Now inputing the values, 

[ 4 * 75watts ] = [ scale * m^2 ]

Now 4 times 75 watts equals 300, so scale is 300, now bare with me on this;

so we have scale as 300; inputting into the right hand side equation,

[ 300 * 0.36 ], where m = 60% is equals to 0∙36:

Now the right hand side equals 108 = [ 300 * 0∙36 ]

The full carrier cw signal on a 100 watt radio equates to the 108 watts calculation, so with a 60% modulation of the ssb carrier sideband, 75 watts is in essence the ssb power meter reading on our new dsp radios.

For a 200watt cw carrier radio:

[ 4 * 140watts ] = [ scale * m^2 ]

scale is [ 4 * 140 ] = 560

so thus the [ 560 * 0∙36 ] = 201, so a 200watts cw radio has in essence a ssb power output of 140 watts.

The only way to up the ssb power output of the radio, is within the dsp software, is to alter the modulation depth of ssb carrier signal. However, even with a 90watt ssb power signal, the modulation index would need to be around 50%, while the output ssb power would be greater, at 50% instead of 60% modulation index, the received ssb signal would sound quieter, as a resolved signal.

With my own 100 watt dsp radio, the mic gain = 50, processor = 50, amc level = 100, mic equ = on.

For us hams within the UK, log on to the "RAF Hack Green" on the internet, find a clear frequency, tune your radio to that frequency, say on the 40m band, and listen to the "RAF Hack Green" signal reception of your transmission.

This is a helpful tool to hear the quality of ones Tx signal. 

I have also done this test, but I originally set up my radio dsp tx software settings with an analogue power meter and an MFJ 300 watt dummy load.

I noticed with the settings derived, the compressor meter readings did not stay max-ed out, but varied in accordance to my voice sound levels.