If you were transmitting CW or FT8 and your amplifier was adding hum
modulation sidebands it would definitely show up on a waterfall of a
station receiving your signal as copies of the primary signal offset by
the hum modulation frequency (e.g. 60 Hz, 120 Hz, 180 Hz, etc).
I think you would hear it on a CW signal as well as seeing it on the
waterfall even with fairly narrow IF filters. For instance, on CW I
think my K3 normally centers the IF passband at an audio frequency of
550 Hz. If I am receiving a CW signal with 60 Hz hum sidebands, I am
going to hear the primary carrier at an audio frequency 550 Hz, and 60
Hz hum sidebands at audio frequencies of 490 and 610 Hz. Even if 60 Hz
is cutoff by the audio filtering of the receiver, it may still be
perceptible as a beat between the 550 Hz primary tone and the 490 and
610 Hz sideband tones. Whatever the case, it is not going to sound like
a clean tone unless the sidebands are low enough. Offhand, I don't know
how low it would have to be before it would no longer be noticeable. I
am sure that has been studied to death.
For an SSB transmitter modulated by a human voice, I don't know if you
would be able to see hum sidebands on a waterfall plot. With a steady
audio tone, you would be able to see it, but with human speech there is
probably too much complexity. Seems like you would be able to hear it,
however, even with the complexity of human speech (assuming the
sidebands were big enough) and even if the audio passband didn't extend
down to the hum frequency. Anyway that's my intuition on this. I am not
sure it is correct.
73, Mike W4EF.................
On 12/18/2024 4:16 PM, Lukasz wrote:
On Wed, 18 Dec 2024, 20:01dj7ww@t-online.de,<dj7ww@t-online.de> wrote:
I use 2µF and no choke with my 3-phase DB6 power supply and nobody hears
any hum.
Very interesting.
Have you ever measured the ripple? If so, what is it?
If you haven't, please give some details of the PSU so I can guesstimate
it. What AC/DC voltage and current do you use, is it a normal 3 phase full
wave rectifier (50 or 60Hz?) or something else (like a doubler, or half
wave etc).
Also, have you had a chance to see a waterfall of your SSB signal? I wonder
if the correspondents can't hear it has to do with the fact everything
under 300Hz is cut off on their end, or there is no hum transmitted? An
waterfall would show any 200Hz peak.
Check with Dr.Alex if you need larger capacitors:
http://www.ur4ll.net/#caps1
Thanks, I've got plenty, but no doubt someone else might need it.
73,
Łukasz - SP4IT
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