Arcs inside the tube do make a large bang if the amplifier does not have enough ESR in the anode system. Everything evil in the world, as disappointing as this may be to you, is not a parasitic. As
Indeed. The 8171 amplifier I built covered the 80m to 15m ham bands. The 8169 amplifier I built covered 1.8MHz through 29.5MHz. cheers, Jon -- FAQ on WWW: http://www.contesting.com/ampsfaq.html Subm
This is not going to happen in the real world because every grid has L and C. The result is a resonance that makes the grid virtually transparent at that frequency. Thus, the output is no longer shi
When a 2000pF vacuum variable arcs, it makes a barely audible sound. Then why do people find that the vhf suppressor R is greatly higher in resistance after a big-bang? Surely. The arc that makes th
The component in the B+ chain that arcs is thus the (RF choke?).....? The destruction can be avoided by fusing the B+ chain with a fast blow fuse? Are we sure that these arcs are not simply filth on
"If the tube has enough voltage breakdown to handle the fundamental RF voltage without problem, we can be sure it will handle almost any spurious oscillation." Is this really true? The unloaded anode
Probably not. The choke is too well insulated from gnd. Fuses do not act to limit peak current, and that is the destructor. Dust would not be able to cause a large increase in R-supp. I have never h
What was the condition of the resistors BEFORE the big bang, Rich? Unless you or anyone measured them right before, we have no we of knowing do we? The fact that they are bad when measured is circums
Well, anything that can be done at 200 MHz can be done at 1 MHz. The tank Q is higher at HF than it is at VHF in a typical HF PA, and the HF stuff dominates the anode current. Not only that, anode l
[chortle] Surely, Jon. 10m FM and RTTY often leave bubbles on the surface of R-supp, however, with VHF parasite damage, the surface typically looks shiny new and the resistance may increase 3x to 4x
Not according to worst case tests performed on the SB-220. Would you like to discuss your assertion that the resistance of nichrome wire increases with a decrease in frequency? -- FAQ on WWW: http:/
Rich replied: Please Rich, enlighten me on how the shiny surface means it was a parasitic, and the bubbled surface means it was HF heating. I'm sure you have a good explanation for that one! ' 73, To
I did not say that a shiny surface means it was a parasitic oscillation. A shiny surface indicates that the outside of the resistor did not get hot. A bubbled surface indicates that the outside of t
I asked: Rich replied: OK. You say a sharp pulse of VHF current heats the resistor from the inside out, while a longer HF current heats the resistor and severely damages the outside. That seems to di
This is my guess as to what took place. The outside is not severely damaged because it is still intact and doing its job of supporting the wire leads and carbon element. Correct. Boiling gold requir
Hi Rich, You replied: Nice guess. But I've never seen reverse skin effect and the thermal conductivity can not be ignored. I don't follow that logic. What causes it to not be damaged? Let me see if I
? say what? Does this have anything to do with your revelation that the resistance of nichrome actually increases as freq. decreases? ? Phenolic is not a good thermal conductor. . ? The resistor is
Tom and Rich, please see my comments below: Hi Rich, Rich or Tom, please forgive me if I misrepresent any of your claims as I haven't been following this debate very closely and hence am not fully ve
But Mike, now that everyone has changed the bad parts and added nichrome the problems went away. Despite the fact that the change in VHF Q is very minor, and Measures original suppressors actually h
As it first did to me, Mike. My guess is that a photon strikes an atom, knocking loose a current carrier/electron, thereby causingthe tube to briefly conduct. This causes several kV to appear across