Hi All, an added thought about the ripple effects:
The ripple voltage is highly dependant on plate current. Considering the
nature of SSB speech wave forms, the maximum ripple voltage only occurs on
speech peaks. Average signal levels would be much lower and the ripple would
also be much lower.
If it was half as much, then the effect would be reduced another 6 dB on
average.
Seems that CW would show the most effects. I do recall hearing a "musical
tone" on some cw signals from Eastern Europe many years ago. Most of the
time it was from high power stations during a DX contest. Perhaps the added
bandwidth of SSB would obscure the ripple. "Lost in the noise" so to speak.
My current interest is mainly in microwave eme operation. Traveling wave
tubes are used to generate power. The homebrew power supplies have a lot of
filter C in the helix supply to reduce hum on the transmitted signal. After
this discussion I am wondering if there may be more C than necessary.
Normally it would not matter but if there is a flashover in the twt the helix
structure could be damaged. There are trip circuits to shut the power supply
down but most of the stored energy would be dissipated in the helix.
73,
Gerald K5GW
I don't recall ever noticing the effect on SSB signals.
In a message dated 10/4/2013 1:31:26 A.M. Central Daylight Time,
ww1c@outlook.com writes:
Gary, ALL
As far as I understand modulation, mixing and multiplication are just
about the same thing. So, if there is an input port to an amplifier that
changes the gain or in other words the output level when all other things
remain
the same, the outcome is a signal which is AM modulated. An amplifier
plate "port" causes gain to vary up and down, this constitutes multiplication
between the input RF and the hum or AF signal. As far as I understand,
there is no need to run a low level active mixer in class C UNLESS you want to
mix two signals coming in from the same port, not from two ports that that
both control the "gate" or the gain of the amplifier.
Whether theory allows it or not, my thinking is that power supply ripple
does cause some AM on all high level tube amplifiers. However how much is
the question, if 10% ripple gives 10% modulation that would mean side-bands
at -20 (power) just 60Hz from the carrier. And if the modulation 10% is
not directly related to the ripple level, then even less noticeable side-bands
would come out. I think this gets interesting with 3 phase power when
here in EU where the ripple voltage is either 150 or 300 Hz depending on the
rectifiers. As you may know, 3 phase 380/240 power to a private residences
is the norm in OH at least.
So, if these side-bands are there, what is the level? Has anybody noticed
them in real life?
BR.
Markku
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