<< The fix that seems to work is: reduce VHF amplification. >> Rich it seems to me that one way to reduce vhf gain would be not to use tubes ( very expensive ones) that have max. ratings to 500 mhz o
True enough, Hank. The 3-500Z apparently oscillates c. 150MHz in the SB-1000, so tube choice is less limited than one might think. . . According to unsubstantiated rumour, the 8877 can oscillate fro
Hi Hank, How do all those big fancy amplifiers with lighthouse tubes or big tubes in cavities with extreme Q's not oscillate? Actually that is exactly backwards. The most stable HF amplifiers use tu
<< The LEAST stable amplifiers use tubes that marginally work at 30 MHz, like 811A's or 572B's. >> Answer me this, since I am in the process of renovating a 30l-1 using 811-A's should I expect this a
A fellow who works for Hughes assured me that they do. Hughes builds a 100kW HF amplifier that uses six antiparasitic devices. I know of an 8877 amp that has an incredible track record. I have teste
Sound practice! 1. Use power device with lowest transfer frequency to achieve the power required. 2. Pay utmost attention to isolating the input from the output. 3. Pay utmost attention to RF bypass
Hank, An important factor (maybe the most important factor) in whether a g-g amp is stable is whether the grid is at rf ground. Once it is not, feedback increases and instability becomes more likely.
RF design is not such a complicate matter, in theory, what's difficult is to deal with and to realize objects that doesn't introduce too many unknown parasitic parameters so modifying, in practice, t
Actually not. The maximum usable frequency of the device has nothing to do with stability. It isn't difficult to understand what the problem is. The problem is at some frequency the grid no longer f
Actually not. The maximum usable frequency of the device has nothing to do with stability. Tom, So what you are saying is that a 3-500Z will oscillate at 1 ghz just as well as a 2c39? Seems that wha
No, if I wanted to say that I would have said that. What I said was the fact the tube has useable gain at a high frequency has no direct relationship to instability. As a matter of fact the most sta
tubes ? Mr. Rauch's statement about grid-resonance is the way it is. When the supposedly grounded grid is resonant, Pandorra's Box is undoubtedly open. ? The source of the VHF seed-voltage is the an
? Well put. ? true ? Good point. cheers, Mauri - Rich..., 805.386.3734, www.vcnet.com/measures. end -- FAQ on WWW: http://www.contesting.com/FAQ/amps Submissions: amps@contesting.com Administrative
Arcs that leave no internal marks. . . . Should a big-bang in a vacuum be heard? An amplifier is normally heavily loaded at the operating frequency. If an amplifier has an intermittent VHF parasitic
If "tinks" in a vacuum can be heard (ie. de-wiskering a vacuum cap), then big bangs in a vacuum should also be heard. Phil -- FAQ on WWW: http://www.contesting.com/FAQ/amps Submissions: amps@contesti
Actually all the banging and tinking you hear from the tube are conducted through the elements to the envelope and then to the air. That isn't the bulk of the noise you hear. The bulk of the noise i
? Rich did not write the following sentence. I wrote the following: vac. cap. tinks can barely be heard. Big bangs are loud. The accompanying flash comes from the HV circuitry. cheers, Phil - Rich..
vac. cap. tinks can barely be heard. Big bangs are loud. The accompanying flash comes from the HV circuitry. The tink can barely be heard because it is a current limited arc. Does anyone care to sac