[Amps] IM distortion and such

[R L Measures]

On Jun 27, 2006, at 11:22 AM, Tom W8JI wrote:

>> Tom,
>>
>> It says it on page two of the Eimac 3-500Z spec sheet. See
>> the one the link was provided for earlier.
>
> Single tone carrier level has absolutely nothing to do with
> operation in a different set of conditions such as two-tone
> modulation at a different anode voltage, bias, and power
> level. You are reading more into the data sheet than it is
> saying.

As I see it, no matter what kind of modulation one is trying to  
amplify, at the point when an incremental increase in input no longer  
increases output (which call the transfer function) by the same  
factor as was observed at lesser currents, the cathode is running out  
steam and the tube is beginning to lose linearity.  Even though there  
is a 3a line on the 3-500Z/ 8002 characteristic curves, does this  
mean that all will be well in linear service at 3 peak anode  
amperes?  If this were the case, at 4kV, single 3-500 linear  
amplifiers could produce 2500w PEP.

OTOH, Tom may be right in saying that tuning up at 550mA produces  
good linearity in an AL-80 or SB-1000, but from the impure matter I  
hear from these two amps on the air that are driven with 100w, I have  
doubts.
>
> For a given set of tuning conditions (load line) a person
> can make the single tone level any level he wants by varying
> drive and the two-tone test will remain the same as long as
> the two-tone power level isn't changed. Single tone and
> two-tone are two totally different conditions, and as the
> data sheets say other operation is permissible.

But there can be no help if the cathode is running out of emission.
>
> Two other random people

What are their callsigns, e-mail addresses, and telephone numbers?

> besides myself have now posted that
> the did the equivalent of a transfer function (which is what
> really measures linearity) and both posted the best
> linearity when the steady-state loadline was established at
> about 550mA.


I don't see how because 550mA corresponds to c. 1650mA peak, which is  
well into the non-linear region.

> Actual performance under one set of conditions
> cannot be determined by extracting data from a test under
> totally different conditions.

Peak emission capability is negotiable?

cheerz, Tom
>
> 73 Tom
>
>
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R L MEASURES, AG6K. 805-386-3734
r at somis.org