[R-390] No reception below 8 mhz, transconductance testing

[Alan Victor]

It sounds a bit far fetched, however, a test circuit could easily be
fabricated for triode, tetrode, etc... that would be plug n play with a
network analyzer. Application testing could be done at the desired
operating frequency.

Alan

On Sat, Feb 18, 2017 at 6:29 AM, Bill Kirkland <b13kirkland at outlook.com>
wrote:

> Never late for change. You could revolutionize the tube industry, ok the
> vintage restoration industry. (but what would all those audio guys do)
>
> Bill
>
> -----Original Message-----
> From: R-390 [mailto:r-390-bounces at mailman.qth.net] On Behalf Of Tisha
> Hayes
> Sent: February-18-17 1:03 AM
> To: R390A <r-390 at mailman.qth.net>
> Subject: [R-390] No reception below 8 mhz, transconductance testing
>
> That is part of my pet peeve even about transconductance testing of tubes.
> If you look up the standard for transconductance test it uses a very low
> frequency (somewhere about 1 KHz if I recall correctly). That's great for
> testing a tube to work in an audio amplifier, it may not be so great for
> something that is running IF (455 KHz) or even RF (up to 30 MHz).
>
> So while transconductance testing does give us some value under AC
> conditions it really does not tell us how that tube is going to work at the
> operating frequency of the circuit.
>
> I had been tempted (only tempted) to modify my TT-1 for IF-like frequencies
> (455) but it would also mean re-calibrating everything to that new
> frequency, pretty much invalidating any comparison to the transconductance
> values that are on data sheets.
>
> Maybe if it was still 1957 it would be a fine activity, to drive a new
> standard for testing tubes for RF/IF operation near their operating
> frequency.
>
> The other thing to do would be to build a circuit to test distortion of
> the amplifier function of the tube, but then it gets even more complicated
> when dealing with gain.
>
>
> *Ms. Tisha Hayes, AA4HA*
>
>
>
> *A sweet romance is not for meI need electricityIf you wanna make me
> flipHit me with a micro chip*
>
>
> *I'll be a diode, cathode, electrodeOverload, generator, oscillatorMake a
> circuit with me*
> *-- The Polecats*
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