On Fri, 24 Apr 98 09:59:03 -0500 Jon Ogden <jono@webspun.com> writes:
>Well, my amp came with about #16 or #18 wire on the supressor and
>that's
>what I continued to use.
YUK!
Most of the anode circuitry was brass sheet
>stock. However, the magnet wire seemed to work fine as the inductor.
"Seemed" tells me nothing.
>
>The wires run hot because they are nichrome which is resistive. In my
>
>model rocketry days, we used nichrome igniters to light the rocket
>engines! They don't necessarily get hot just because of their size.
Unless you plan to launch the 4-1000A I fail to see your point. You can
use a material that has the desired loss at VHF but should not require
silver solder in normal operation at say 40M...or even 10M for that
matter. I run key down for a full minute and with a very rapid PS bleed
the suppressors are just barely warm to the touch. That tells me they are
doing the job efficiently and not simply wasting heat.
>That provides some heat, but not most of it, IMHO. The majority of
>that
>heat is because they are resistive.
Nichrome is resistive at DC also...thats why I do not use it in a RF
path.
>
>
>>Another problem I have with Rich's suppressors is that they will not
>work
>>on 6M. I get lots of broken amps in here with those suppressors. I
>>normally rip them out as a matter of course and try and cure the
>>problem...not the symptom. Anyway, I have tried and fried those
>>suppressors almost instantaneously in a 6M conversion even with
>572B's.
>
>I wouldn't expect them to work there. And I don't think Rich
>advertises
>his as working there either.
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.
>
>I had a HORRIBLE time getting my inductor to work in my original
>supressor. I followed all the advice in literature and wound about 4
>turns. Resistor blew up (metalized film resistors too). Took off
>turn,
>still blew up. 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.
>would suspect that at 6 meters, you'd need even LESS inductance.
A properly engineered suppressor should work on either band. A typical
ham schlock suppressor is a gamble in either case.
>
>
>>Once you can divorce yourself from the old carbon composition
>resistance
>>and changing values and switch to a better R; then tube aging, or
>>whatever will not be an issue. In fact, as a tube ages the gain and
>>therefore the susceptibility to oscillation decreases. A metal oxide
>>resistor does not have the thermal problem of carbon comps....neither
>>does a Globar or that 20W pure carbon that Peter likes.
>
>An aging tube will certainly tend to have its tendency to oscillate
>decrease. However, what about a brand new tube?
Your original question concerned the aging of a tube. I always base my
assumptions on NIB specs, not some unknown pull.
>
>>Do yoursel a favor....go to Dayton and pick up a 50 Ohm 20-50W
>>Carborundum style resistor. Wind the L from 1/2" wide copper strap
>and I
>>will bet you a dinner you will never have a parasitic or overheated
>R.
>
>A 50 Watt resistor would be great! That would work well.
They still show up but a 20W will do you fine.
>>
>>One of my better finds at Dayton a few years ago was a case of 100
>>Carborundum 50 Ohm resistors. They were all sealed in individual foil
>>envelopes and had the designation " 5905-107-8237, Resistor, Fixed
>Comp,
>>1ea Mfr P/N SP5X5/8 and dated 04/66. The seller was an obvious Duh
>What
>>type and it took under 2 minutes to buy the whole lot for $10. Heck,
>he
>>probably got them for nothing at some military dump. I believe these
>are
>>25W rated and are a compact 5" L and .75" wide.
>
>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.
>
>>>Yes, layout even at HF is EXTREMELY critical and can solve many a
>>>problem. Agreed. However, a 4-1000 still has gain up at 150 MHz
>and
>>>many of the tubes today go much higher. If the anode circuit is
>>>resonant
>>>at 75 or 80 MHz, please tell me how you are going to move it 70 MHz
>>>higher, let alone 20 MHz higher with a coil and resistor.
>>
>>You are missing the point entirely Jon....I am not talking about the
>>tubes parasitic frequency....that should be taken care of by the
>>suppressor. What I am talking about is other circuit resonances that
>are
>>typically well over 100Mhz and can then possibly be manipulated to
>where
>>the gain drops in the case of most glass tubes.
>
>Uhhh....neither am I Carl. I am talking about a MEASURED resonance in
>
>the anode output circuit. The tube characteristics is the main thing
>that contributes to that resonance. I am not talking about the tube
>by
>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.
Yes, yes, in reality they interact BUT you do not design the suppressor
for what happens on the right side of the blocking cap.
>>>
>>>It's an interesting idea. Although, I do believe that you could put
>a
>>>cap in series or in shunt. And series circuit can be turned into a
>>>parallel equivalent circuit and vice versa. Although a series cap
>>>across
>>>the bandswitch might be easier.
>>
>>Adding 10-15pf in shunt in many amps would then not permit use on
>10M.
>
>I didn't say what value...You said that at National you used a series
>cap
>instead of a shunt cap. All my point was that a series circuit can be
>
>transformed to a parallel circuit.
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.....??
>
>>
>>I agree on filter resonances but in the pure sense I do not believe
>that
>>is the problem. In a real world tube amp with discreet components,
>point
>>to point wiring, etc you have many, many sources of spurious
>resonances.
>>Not only do you have all the various coupling from component to
>component
>>and to ground but in some cases the actual dimensions of the plate
>>circuit enclosure come into play. The possibilities can be
>overwhelming
>>and therefore the low Z series cap is a rather simple way out in
>>many...of course not all...cases.
>>
>
>Agreed.
>
>>>
>>>VHF oscillation. So oscillations can cause arcing.
>>
>>
>>Of course...I have never denied that nor has anyone else that I am
>aware
>>of. BUT there is a big difference between parasitic caused problems
>due
>>to a tubes internal geometry and a purely external resonance source.
>You
>>and others have to think about keeping the two isolated...at least
>for
>>discussion and the individual cures required.
>
>This is true. Not every sickness requires the same cure.
>>> My experience with parasitic
>>>oscillations
>>>has not been of the "big bang" type, but I do not dispute that it
>>>could
>>>happen.
>>
>>Well, there we differ...I do dispute 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.
Any current flowing through a wire
>produces
>a magnetic field. Get that current high enough and you can move
>things
>with it.......
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.
>
>Also, if the feedback path that occurs is such that a VHF parasitic is
>
>fed from the anode to the cathode in phase, then you have a positive
>feed
>back situation. Very, very, very rapidly, will the level of that
>signal
>increase and increase and increase until the point where something
>does
>break down since all that energy is running around in there and not
>getting canceled out.
That example takes a finite amount of time...at least a second or more.
A bang is measured in milliseconds.
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.
It usually happens in early prototypes where
>you
>have a poor layout.
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.
Of course, how many homebrew amps have
>professional
>layouts....very few IMHO.
Many HB have better layout than cost conscious ham mfg amps. Then there
are the bozos that use zip cord at 5KV !!
>
>My statement above then about not having seen big bang stuff may sound
>
>contradictory then. Let me clarify, I haven't seen big bangs with
>tubes.
Yet you profess to accept a theory with no proof! That is strange
behavior for a trained EE.
> 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!
>
>>But yet according to Wes Hayward's web page and Tom Rauch's input,
>Rich's
>>stuff does nothing for lowering VHF Q. We all know Rich claims
>otherwise
>>but how come Hayward disavows his conclusions and has gone so far as
>to
>>publish his own page in refute????? Something has a decided dead
>fish
>>smell IMO.
>
>Well, I don't know about Wes, but Tom Rauch has resorted to personal
>insults to defend his position. So IMHO, he doesn't have a lot of
>credibility. This is regardless of how right he may be.
Apology...I meant Wes Stewart....not Hayward. Sorry for the mixup.
Anyway Tom seems to have found a home and protector over on the Topband
reflector where the Admin wont permit any criticism...
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" .
73 Carl KM1H
>
>
>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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