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[AMPS] parasitics

To: <amps@contesting.com>
Subject: [AMPS] parasitics
From: jono@webspun.com (Jon Ogden)
Date: Fri, 24 Apr 98 15:57:07 -0500
>
>But a good suppressor should work at 50MHz also. If the natural parasitic
>of a 3-500Z is somewhere around 130MHz why on earth would you use a
>suppressor that can barely perform at 28MHz? There is no rule that you
>have to design a suppressor based on the frequency of normal
>operation.....you design the suppressor based upon the tube and then it
>is stable wherever you want to use it.
>Rich's comment about 6M being VHF is just a bunch of bluster since the
>natural parasitic of the 3-500, 572B and most common ham tubes is well
>above 50MHz.

You bring a good point here.  However, in the case for my amp, I don' 
think the orginal supressor I made would work.
>
  It was down to ONE turn before it worked correctly. 
>
>
>With #18 wire I dont doubt it. I have never seen a 4-1000A circuit using
>such a ridiculous suppressor.

Well, I was only following what I read in both the ARRL Handbook and 
W6SAI's book (including a c.1972 copy).  It is amazing how unhelpful most 
of the literature is out there concerning amps.
>
>A properly engineered suppressor should work on either band. A typical
>ham schlock suppressor is a gamble in either case.
>
So I guess I am a schlock designer!  :-)  Some would probably argue that 
it's true....I try to make do with what I have.  Before I discovered this 
mail reflector, I harldy knew where to go for parts, etc.


>>Great story.  However, unfortunately, I won't be going to Dayton this 
>>year.  :-(
>
>Neither will I but I just mentioned that find to stress that for the
>homebrewer there are goodies still available...you cant sit on Internet
>all day and expect them to come to you. 

Agreed.....
 
>>itself.  Even with a parasitic supressor in place, there is still a 
>>resonant dip in the entire circuitry.  The supressor supresses the 
>>parasitic resonance.  It does not eliminate it - hence its name.]
>
>
>Again you are completely missing the point. For extreme simplicity just
>visualize the amp plate circuit as 2 distinct circuits. One on the left
>side of the plate blocking capacitor and the other on the right side. 

ARRGH!  Carl, no I am not missing any point.  I couple my GDO to the tank 
coil...I see a resonance at say 14.250 MHz.  I couple my GDO to the 
supressor inductor, I see a resonance at 85 MHz.  Sure I am using 
different coils, but the entire circuit is still resonant at 85 MHz.  
This is with the tube in place.  Not without it in place.  If the circuit 
is resonant at 85 MHz, it is resonant at 85 MHz.  I don't know why we 
can't agree with this.  When a GDO shows a resonant dip in a circuit it 
is obviously resonant there as it sucks out energy from the GDO.  Unless 
I am a totally dense dipwad, I don't understand what you are getting at.  
Airhead maybe (I'm blonde), dense dipwad, no.

>Yes, yes, in reality they interact  BUT you do not design the suppressor
>for what happens on the right side of the blocking cap. 

Depends on which side of the amp your tube is on.  On the right side of 
my blocking cap is my supressor circuitry.  On the left side is my tank 
circuit.  So I am designing the supressor for the side of the circuit 
that includes:  tube, plate RFC, supressors, blocking cap and tune C.  
Seems like that's what you gotta design for.  

>
>You didnt have to say what value...there is a finite limit and the range
>is not very wide. I also asked you to analyze that suggestion.....??

True.  I don't have time to analyze it and I haven't been following the 
discussion of the caps all that well.  So perhaps someone else can pitch 
in and do that.

>>Well, I guess we do.  Rich is correct when he says that a magnetic 
>>field 
>>produces a mechanical force.
>
>
>If you are quoting from a textbook then a resounding YES.

Hmmm...You doubt that current flowing through a wire causes a magnetic 
field and that a magnetic field has a magnetic force?  How does a motor 
turn then?  Or better yet Carl, take a nail, wrap some enameled wire 
around it and hook that enameled wire up to a battery (strip the 
enameling off the ends first).  Then hold the nail above a pile of paper 
clips.  I think you will see plenty of mechanical force.

I don't need to quote a text book to do that.
>
>I will try AGAIN....explain only...not hyperbole...how a 3-500Z filament
>can be bent. If you have to resort to EE math do it. What I cant follow
>my son can.

Now, imagine that same sort of magentic force except instead of a 1.5 
volt battery, you have a 6 Kilovolt supply with a capability of 2 amps of 
current.  That's 12,000 Watts.  Did you know that mechanical power is 
also expressed in Watts?  Hmm..could there be a reason....  Ok now hold 
that nail with 6 KV and 2 A of current next to a cage of fairly thin, but 
white hot wires.  What do you think will happen?  Do you think there will 
be a magnetic field around that wire?  What happens to metal when it is 
white hot?  From watching blacksmiths when I visited Plymouth Plantation 
as a kid, I learned that white or red hot metal is malleable and 
flexible.  I'll leave you to figure out the answer.

Hyperbole?  Maybe.....
>
>
>That example takes a finite amount of time...at least a second or more. 
>A bang is measured in milliseconds.

Try to determine your reaction time.  You wouldn't notice the oscillation 
at first.  By the time you do and then can react before *bang* I think 
there could easily be more than a second.  And I think it's a lot less 
than a second....  Of course, we are both speaking in hyperbole here.
>
>
>>  I've seen lots of transistor amplifiers go 
>>*POOF* 
>>due to this happening.
>
>Sorry, but that example has absolutely ZERO meaning in a tube circuit.
>

Please tell me why?  Tubes are very much like FETs.  I fail to see why a 
failure mode in a solid state PA couldn't happen in a tube.  The only 
thing is tubes ARE more rugged and can take more abuse.
>
>
>I have zapped my share of SS stuff...it is a totally different scenario
>but I can see that with really no tube experience you use that example.

Quote from a textbook as to why.

>Many HB have better layout than cost conscious ham mfg amps. Then there
>are the bozos that use zip cord at 5KV !!

Not me....
s. 
>
>Yet you profess to accept a theory with no proof!  That is strange
>behavior for a trained EE.

Carl, do you know what the "Scientific Method" is?  The first stage is a 
word called HYPOTHESIS.  Now I know that's a big word for some hams, but 
it really is a real word.  A hypothesis is nothing more than an educated 
guess.  Based on a hypothesis experiments are conducted.  Based on those 
experiments, the hypothesis is proved right or wrong.  If it is right it 
becomes a theory.  With more experiments the theory is proven right or 
wrong.  If right it becomes a law (such as Netwon's Law's etc.).  By 
definition a theory does not have complete proof.  Einstein's Theory of 
Relativity has not been proven.  If is had been, it would be the "Law or 
Relativity."  There are theories on the existence of magnetic monopoles.  
Yet there is no proof of them.  The whole science of particle physics 
(quarks, etc.) is based on theory without a lot of real proof.  I could 
go on.  It's the dullard in society that can't accept anything without 
concrete proof.
>
>
>> Although, I have seen the plates of my 4-1000A glow a really, really 
>>nice cherry red color.
>
>That is about normal color for a "serious" 4-1000A amp. I would hate to
>see you around a pair of 250TH's or similar!

Ok.  I still get nervous about it.  But if you say so.....

>
>Anyway Tom seems to have found a home and protector over on the Topband
>reflector where the Admin wont permit any criticism...
>
Remind me not to join that sig.

>I think that this is one of the absolutely BEST ham/technical reflectors
>available and thanks to Admin for not being a jerk  or a "Nazi" .

Yes...This is great.


By the way, a went to lunch today with a Ham friend of mine.  He recently 
bought an Alpha 374 from another friend of his.  His friend told him that 
he was having all sorts of problems blowing up tubes constantly until he 
installed an AG6K parasitic supressor.  Now the amp works fine and no 
more blown tubes.  And my friend verified it.  He said the amp works 
great.  Imagine that...an amp with nichrome wire that works well!

Theory without proof?  Sounds like proof to me...

73,

Jon
KE9NA


--------------------------------------------------------------------------
Jon Ogden

jono@webspun.com
www.qsl.net/ke9na

"A life lived in fear is a life half lived."




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