Why more power on SSB?

[hammer0630]

This may be a very dumb question but here goes anyway! A typical amplifier may state in it's advertising 100 watts AM and on SSB 200 watts. Is this only because SSB is 3X the wattage of the AM side? What I am wondering is if you have a modulation swing of 12 watts on AM would you then get 200 watts out of the amplifier on AM? I ask this because I have a DK of 2 watts and a modulation swing to 15 watts and seem to get more watts out of my amp than it is rated for on AM.

 

[Captain Kilowatt]

Amp ratings are pretty much whatever the manufacturer wants to say they are and bear little resemblance to reality. SSB is not three times the AM either BTW. It has long been accepted that was the case but it depends on modulation levels and whether or not your radio has been worked on. If you will, notice amateur radio amps only have one rating and that is pep output which can be related to any mode beit AM, SSB, RTTY, CW or anything else. CB amps tend to rate the output on SSB as twice the AM rating a lot of the time. Typically an amp, any amp, can produce more pep power on SSB that it can on AM (if it has the headroom without distortion) simply because of the heat produced by the constant carrier in AM mode. This limits the power from the amp as it will run much hotter in AM mode than in SSB mode.

 

[KM3F]

For a different type of reference, the stock CB radio at 4 watts carrier is 16 watts peak at 100% modulation where as the stock SSB is usually 12 watts peak power.
Actually less power on SSB in normal stock unmodified form.
The reason SSB seems like a higher power level is all in the SSB receivers both ends of a contact.
The bandwidth and sensitivity is greater in SSB allowing a quieter receive making less power an advantage over AM.
Why this is is with the elimination of the AM carrier all the audio power is put into making power within 1/2 the bandwidth so it has a huge advantage over greater distances.
When rating amplifiers it is a different situation that depends on the reasonable distortion free peak power and what reference is used.
For example in a Ham radio rated at 100 watts SSB peak power, the AM function can only be 25 watts carrier.
How this comes about is just like the AM CB that at 100% modulation 25 watts x 4 = 100 watts same as CB 4 watts x 4 = 16 watts.
The same standard applies no matter what radio unless the mfger has designed in a different power rating determined by the devices used in the radio design..
On amplifiers the same rules apply for AM and SSB as long as the true capability of the amplifier is specified and not misunderstood or mis represented.
After all the outboard amplifier works the same as one in a radio and subject to the same rules.
When operators drive beyond these rules, it's misuse and abuse of equipment along with the interference cause from harmonics and splatter plus equipment failures that often result.
Peaking of radios and lack of understanding of these basics result in overdriven equipment in the mistake it is ok to do so and just throw out engineering from shops charging for mis adjustment to this misuse, and owners feeling they know better than engineering and just because other do it.
Good luck.

 

[Captain Kilowatt]

I suspect the reason the OP stated that SSB is three times the AM output is the way that CB radios were rated at 4 watts AM and 12 watts pep SSB. This has lead many,many people to erroneously believe that any given radio will produce three times the power out on SSB as it will on AM which is not the case. Individual voice characteristics are too varied to make such a blanket statement. I like a pep rating as that allows one to determine the available power output in any mode whether a carrier based mode like AM,FM,CW or suppressed carrier modes like SSB.

 

[hammer0630]

Very interesting answers! I thought I was asking a very dumb question but I think your in depth answers has probably enlightened many of us!