Hi,
I found the full power supply specification in some old documents. This is
very surprising ,because usually in manuals there is a note that technical
specs are classified.
So what did they consider acceptable ripple for the military? 0.8% at 850mA
! This is only 24V at 3000V. How on earth did they achieve that with a
choke and a 2uF capacitor? Perhaps the idea of it being in some sort of
resonance and requiring constant minimum current as a result is the closest
to the truth.
But now the question becomes, how do I check how far from resonance am I
(other than by measuring ripple)? I've obtained the capacitor they most
likely used originally. And the choke is original too.
73,
Łukasz - SP4IT
On Tue, 24 Dec 2024, 15:43 David G4FTC, <g4ftc@hotmail.com> wrote:
> Hi Michael,
>
> All understood. It was just that I hadn't seen anyone make a mention of
> WebSDRs, so I thought it may be a helpful reminder.
>
> I find WebSDRs very useful for both own signal monitoring and also
> checking propagation paths.
>
> Happy Christmas to all.
>
> David G4FTC
>
> Sent from Outlook for Android<https://aka.ms/AAb9ysg>
> ________________________________
> From: Amps <amps-bounces@contesting.com> on behalf of Michael Tope <
> W4EF@dellroy.com>
> Sent: Monday, December 23, 2024 7:46:44 PM
> To: amps@contesting.com <amps@contesting.com>
> Subject: Re: [Amps] Acceptable ripple on high voltage plate power supply
> in tetrode amplifiers.
>
> Hi David,
>
> I was trying to address a particular comment that Lukasz SP4IT made,
> which was:
>
> /"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." /
>
> My point was that by switching to CW or sending a pure tone on SSB, it
> would be easy to see hum sidebands on a waterfall or spectrum analyzer. As
> to whether any particular tube amplifier will generate hum sidebands,
> others have commented on the fact that class AB amplifiers have good anode
> supply rejection ratio compared to class C amplifiers. That isn't
> intuitively obvious to me, but I trust it is correct.
>
> I do agree with you that using an SDR is a great way to assess ones signal
> quality.
>
> 73, Mike W4EF.................
>
>
>
> On 12/22/2024 3:14 PM, David G4FTC wrote:
> > I've been following this thread with interest.
> >
> > Could I suggest listening to your own transmitted signal on a local
> WebSDR?
> >
> > You can then assess if the ripple is excessive or not.
> >
> > Regards
> >
> > David G4FTC
> >
> > Sent from Outlook for Android<https://aka.ms/AAb9ysg>
> > ________________________________
> > From: Amps<amps-bounces@contesting.com> on behalf of Michael Tope<
> W4EF@dellroy.com>
> > Sent: Sunday, December 22, 2024 5:08:23 PM
> > To:amps@contesting.com <amps@contesting.com>
> > Subject: Re: [Amps] Acceptable ripple on high voltage plate power supply
> in tetrode amplifiers.
> >
> > 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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