On Dec 23, 2005, at 3:11 AM, Steve Thompson wrote:
> A few thoughts covering several recent posts:
> Stability with tetrode amps should not be a problem if you use ceramic
> tubes with the proper bases. More than anything, I think it's the lead
> length in glass tubes that brings problems.
For VHF and UHF amplifiers, I found this to be true, but for HF ones,
to my surprise, things blew. As I see it, whereas lanky glass-tubes
can have VHF parasites, compact ceramic ones can have UHF parasites. I
think it's advisable to remember that at 300MHz, the output (anode) to
input (cathode) feedback path in an 8877 has c. 5000-ohms of reactance,
which is nothing to sneeze at with 4000v on the anode.
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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