I would think so. However, there have been more than a few reports of
this occurrence with solid-state radios. Perhaps the reason is that
Chebyshev and Butterworth band-pass filters used in solid-state
transceivers contain series capacitances which may short under a voltage
transient, thereby delivering energy to the final transistors. On the
other hand, tuned input Pi-network capacitors are in parallel with the
signal path, so a short to ground would seem to stop energy from entering
the radio.
>Okay, I'll buy this one. But I have a question. Wouldn't the low pass
>filters in the radio have some effect on reducing higher frequency
>energy from getting at the PA?
>
>Martin
>
>
>-----Original Message-----
>From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
>On Behalf Of rlm
>Sent: 18 March 2003 20:17
>To: Tom Rauch; AMPS
>Subject: Re: [Amps] 813 No parasitics
>
>
>
>
>>
>>> Ok, you asked Skip; but let me suggest or better saying, ask, could
>>> be the 30 MHz highest frequency for full ratings?, or maybe at lower
>>> ratings you could have parasitics also?.
>>
>>As a general rule the most difficult to stabilize tubes are tubes with
>>low upper frequency limits. The grid and anode leads inside such tubes
>>are usually thin and long.
>>
>The 811A & 572B being examples. On the other hand, G-G triodes with a
>low-L grid that have substantial VHF gain can also become squirrely in
>HF
>amplifiers. The 3cx1500A7, 3cx3000A7 and the 3cx6000A7 are examples,
>This week, I heard about a 3cx6000A7 amplifier project that was being
>driven directly by a FT-1000D. The amplifier made a bang. At the same
>instant, the finals shorted in the 1000D. The lesson: a G-G tuned input
>
>circuit not only acts as a low-pass filter to keep VHF harmonics out of
>the amplifier, it acts to keep VHF energy from the amplifier from
>travelling back into the radio and causing a problem.
>-- Amplifier engineers would do well to pay attention when the
>technical specification sheets say "Maximum Ratings for Amplifier and
>Oscillator Service".
>
>- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
>www.vcnet.com/measures.
>end
>
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>
>
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
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>
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
end
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