The concept of a "suppressor" is to suppress the parasitic from even
starting. The Q of the strap, wire, coil, has nothing to do with the design.
This is where the voodo starts.
The coil of the suppressor should be broadly resonant at the parasitic
frequency of the tube which varies from type to type. This is why different
number of coil turns are used.
The resistors sole purpose is to stop the parasitic from even starting,
ideally it absorbs no power. I call it a snubber. It naturally De Q's the
coil which can be taken too far with a too low a value and start absorbing
power on 10M. This gets critical with 1929 era designs and their offspring
such as the 811 and 572B where the parasitic is down in the low VHF region
as compared to in the 100-150 mHz area for most other popular glass bottles.
The 50's QST articles I mentioned earlier give a good explanation without a
lot of math. They are available in the CD Rom set or on line to members at
ARRL.com
The nichrome is simply a series resistor with little appreciable L. As such
its a power absorber which can reach over 100W in a SB-220. The 3W MOX
tacked somewhere in the mess is simply along for the ride and also absorbs
power.
The suppressor Ive described previously tames an otherwise stock Clipperton
L even with Chinese tubes on all bands. It is possible to get 1200W on 10M,
hold the key down for 30 seconds, and nothing bad happens. The resistors
dont even get beyond barely warm. In a FL-2100Z or SB-200 even Svetlana
tubes are completely docile.
This was something else I described on here in the 90's which was enacted on
a commercial 572B amp.
A 4-1000A is an easy tube to tame once the builder realizes what has to be
done. Sloppy layout and wiring is the major problem. In the 80-90's I built
to order many 1-2 tube swamped grid driven versions and a few GG. It didnt
take much more than a GDO in diode mode to understand where the instability
occured. BTW, 3 x 120 Ohm 2W was what I used right thru 10M.
Carl
KM1H
Interestingly when I asked W6MTF at Eimac for some advice regarding
parasitic suppression when I was first building my 3CX3000 amp a decade or
so ago, he immediately advised me not to bother with suppression - just
connect the anode choke to the anode with whatever comes to hand, but keep
it short. I never asked why - though it's occurred to me since to wonder
how he knew that I'd have no problems. Maybe I'll ask him.....
Isn't the real cause that the tube and/or circuit has Q at VHF? So isn't the
'cure' that we try to lower the Q at VHF whilst trying to keep Q at the
fundametal that we're interested in? It may be a moot point as to whether
we're treating cause or effect. Search me, mate. That's too deep a
question at this time on a Saturday night after a few glasses.
In my 4-1000A amp I experimented with all sorts of suppressors but
eventually settled on three paralleled 100R resistors with a couple of
twists of some 4mm copper wire that fell out of a junk box. I can explain
how it works (I think) but couldn't predict what would work. Where does the
fine line lie between science and voodoo? If there are too many variables
to predict what will work, so we just try stuff till it works then is that
science or voodoo?
Cheers
OILy
-----Original Message-----
From: "Alek Petkovic" <vk6apk@bigpond.com>
To: "Carl" <km1h@jeremy.mv.com>; "Amps" <amps@contesting.com>
Sent: 13/03/2010 23:06
Subject: Re: [Amps] Clipperton-L parasitic suppressors
At 08:52 AM 13/03/2010, Carl wrote:
>Lots of things work Alek, there are enough poorly designed amps on
>the market that prove that.
>
>I prefer to attack the problem; and not the symptom and lose a few
>hundred watts on 10M to heat.
That's gotta be the "Classic Line Of The Week" mate.
I mean what is a parasitic suppressor? What is any parasitic
suppressor? Is it not something that "attacks the symptom and not the
problem"? Whether it is made of strap, copper, stainless steel,
Nichrome, has Silver Mica capacitors, 100 Ohm resistors, 50 Ohm
resistors or whatever, it is still a device which attacks "the symptom".
Throughout the ages, it has been found that a number, if not all, of
the methods listed above, are effective in reducing the symptom. None
of them attack the problem.
If you effectively attack "the problem", you would not need to use a
parasitic suppressor at all. Are you suggesting that we can all
design, and build our amplifiers in such a way that we do not need to
use these devices?
We know that certain tubes, depending on their construction and their
electrical characteristics, are less prone to the problem than
others. In those cases, the problem is solved and you can get away
without a suppressor. Would you be brave enough to put a 3-500Z or
572B or 3-1000Z amplifier which has no parasitic suppressor/s onto
the market? No, of course not. You would have to include suppressors
in case that "symptom" ever reared its ugly head.
Cheers and thanks,
Alek.VK6APK
>It also goes back to basics. Why do only a handful of untrained ham
>hobbiests fall for the voodo while engineers from all corners of
>the planet condemn it?? What commercial amp uses voodo suppressors?
>What tube manufacturer champions them?
>
>Measures was banned from this reflector for his stand and obvious
>completely wrong theories.
>
>Im not going to get in a long winded discourse on this, the feelings
>on here run deep and Ive no desire to start it anew. Anything you
>might want is in the archives going back to the 90's when I first
>joined. You will find a long list of respected engineers represented.
>
>Carl
>KM1H
>
>
>>At 06:57 AM 13/03/2010, Carl wrote:
>>>No offense Alek but the masses on here dont believe in voodo science as
>>>they
>>>do on the forum you just arrived from. You might want to search the
>>>archives
>>>on the subject.
>>
>>Ha ha. No offense taken Carl. You won't offend me in a hurry.
>>Number 1, I'm married. Number 2, I live by the principle that if
>>you strike a match, then don't cry to mummy (you say mommy) that
>>the fire is too hot. I lit the match so I gotta take the flame.
>>
>>You are probably right about voodoo science but all that is quite
>>irrelevant to me, because I know from my own experience, that they
>>do actually work. I'm satisfied with that.
>>
>>>Larry, for a real suppressor that works get a Xicon 50 Ohm 5W MOX
>>>resistor
>>>and a pair of 100pf 500V silver micas for each suppressor from Mouser.
>>>
>>>Lay a resistor and the original (or a clone) in parallel. Connect a cap
>>>between them at both ends. Wire it dead bug or on perf board.
>>
>>You said a pair of SM caps for each suppressor. Do you put the 2
>>caps in series to give you 50pF @ 1kV and then put that in parallel
>>with the coil and resistor?
>>
>>If so, then I am interested enough to try it out on my Clipperton L
>>which is also being done up. I just got a Ameritron plate choke in
>>the mail this week so I'll be installing that next weekend, along
>>with the .01uF at the base. I have a bundle of 50 Ohm, 5W MOF
>>resistors and 100pF SM caps, so I will do up the suppressors as well.
>>
>>Cheers, Alek
>>VK6APK
>>
>>
>>>Carl
>>>KM1H
>>>
>>>
>>>----- Original Message -----
>>>From: "Alek Petkovic" <vk6apk@bigpond.com>
>>>To: "Larry" <w6nws@arrl.net>; "Amps" <amps@contesting.com>
>>>Sent: Friday, March 12, 2010 4:57 PM
>>>Subject: Re: [Amps] Clipperton-L parasitic suppressors
>>>
>>>
>>> > G'day Larry,
>>> >
>>> > At the risk of offending the masses, don't worry what value they are.
>>> > Just go to http://www.somis.org and scroll down to
>>> > <http://www.somis.org/Price-Info.html>Price List--Information Sheet
>>> > and order yourself a kit for 4x572B. Much simpler and much better.
>>> >
>>> > If you still wanna know the value of the original, they are as you
>>> > said. In the circuit they are R6 and R7 and the parts list quotes
>>> > them as being 100 Ohm, 2 Watts.
>>> >
>>> > Cheers, Alek
>>> > VK6APK
>>> >
>>> > At 05:33 AM 13/03/2010, Larry wrote:
>>> >>I have cleverly filed my Clipperton-L doc. I am hoping someone can
>>> >>help. The parasitic
>>> >>suppressor resistors have broken. I believe they are 100 ohm 2W
>>> >>composition. Can
>>> >>anyone confirm the value? I am not sure what caused the breakage at
>>> >>this point.
>>> >>
>>> >>73, Larry W6NWS
>>> >>_______________________________________________
>>> >>Amps mailing list
>>> >>Amps@contesting.com
>>> >>http://lists.contesting.com/mailman/listinfo/amps
>>> >
>>> >
>>> > http://www.qrz.com/db/vk6apk
>>> > http://www.qrz.com/db/vk6py
>>> >
>>> > _______________________________________________
>>> > Amps mailing list
>>> > Amps@contesting.com
>>> > http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>_______________________________________________
>>>Amps mailing list
>>>Amps@contesting.com
>>>http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>http://www.qrz.com/db/vk6apk
>>http://www.qrz.com/db/vk6py
>>
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