[Amps] Acceptable ripple on high voltage plate power supply in tetrode amplifiers.

[Michael Tope]

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 at t-online.de,<dj7ww at 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
>