>
>
>The last time I saw #20 in a suppressor was for a 6146. Any suppressor
>for a 3-500Z that I am aware of uses #12 or 14 and real quality ( read
>stable) amps use strap.
>
>I would not even attempt anything under #10 for a 4-1000A.
>BTW, also note that those little bitty #16 wire kits include silver
>solder since they run so hot...not a good engineering practice IMO.
Well, my amp came with about #16 or #18 wire on the supressor and that's
what I continued to use. Most of the anode circuitry was brass sheet
stock. However, the magnet wire seemed to work fine as the inductor.
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.
That provides some heat, but not most of it, IMHO. The majority of that
heat is because they are resistive.
>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.
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. I
would suspect that at 6 meters, you'd need even LESS inductance.
>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?
>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.
>
>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. :-(
>>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.
>>
>>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.
>
>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. Any current flowing through a wire produces
a magnetic field. Get that current high enough and you can move things
with it.......
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. I've seen lots of transistor amplifiers go *POOF*
due to this happening. It usually happens in early prototypes where you
have a poor layout. Of course, how many homebrew amps have professional
layouts....very few IMHO.
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.
Although, I have seen the plates of my 4-1000A glow a really, really
nice cherry red color.
>
>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.
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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