I have just looked up the filter arrangements for my RF104. It comprises of an
8H choke with a 6uF capacitor. But this is for a single phase supply as opposed
to your 3 phase supply.
To stabilise the ht voltage, two bleeder resistors each 50k 160W are used in
series between the HT and ground.
Hope this helps
David G4FTC
Sent from Outlook for Android<https://aka.ms/AAb9ysg>
________________________________
From: Amps <amps-bounces@contesting.com> on behalf of David G4FTC
<g4ftc@hotmail.com>
Sent: Wednesday, December 25, 2024 8:28:21 AM
To: Lukasz <sp4it.mail@gmail.com>
Cc: amps@contesting.com <amps@contesting.com>
Subject: Re: [Amps] Acceptable ripple on high voltage plate power supply in
tetrode amplifiers.
Hi Lukasa,
The choke - capacitor arrangement is typical in Switched Mode Power Supplies.
Ripple can be reduced to very low figures by a suitable combination of L and C.
There are trade-offs between a high L and a high C.
FYI I have a Harris RF104 amp which uses an L-C filter, but this requires a
bleeder R to avoid the HT voltage increasing under no-load.
Regards
David G4FTC
Sent from Outlook for Android<https://aka.ms/AAb9ysg>
________________________________
From: Lukasz <sp4it.mail@gmail.com>
Sent: Wednesday, December 25, 2024 5:13:11 am
To: David G4FTC <g4ftc@hotmail.com>
Cc: Michael Tope <W4EF@dellroy.com>; amps@contesting.com <amps@contesting.com>
Subject: Re: [Amps] Acceptable ripple on high voltage plate power supply in
tetrode amplifiers.
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<mailto: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<mailto:amps-bounces@contesting.com>> on
behalf of Michael Tope <W4EF@dellroy.com<mailto:W4EF@dellroy.com>>
Sent: Monday, December 23, 2024 7:46:44 PM
To: amps@contesting.com<mailto:amps@contesting.com>
<amps@contesting.com<mailto: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<mailto:amps-bounces@contesting.com>>
> on behalf of Michael Tope<W4EF@dellroy.com<mailto:W4EF@dellroy.com>>
> Sent: Sunday, December 22, 2024 5:08:23 PM
> To:amps@contesting.com<mailto:To%3Aamps@contesting.com>
> <amps@contesting.com<mailto: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<mailto:20%3A01dj7ww@t-online.de>,<dj7ww@t-online.de<mailto: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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