[Amps] 4CX250 IMD

[jeremy-ca]

----- Original Message ----- 
From: "Steve Thompson" <g8gsq at eltac.co.uk>
To: <amps at contesting.com>
Sent: Monday, October 01, 2007 3:08 AM
Subject: Re: [Amps] 4CX250 IMD


>
>> This thread has me wondering how accurate IMD or even PEP was measured
>> in the late 50's, early 60's. Would the readings that National provided
>> for their 4CX1000A military amp hold up to todays techniques and
>> instrumentation?
> My guess:
>
> Comparison against fixed attenuators using either spectrum
> analyser or receiver should give fairly good accuracy of relative
> values.
>
> Calibrating a diode detector against cw should give reasonably
> accurate pep readins.
>
> Steve


Thats exactly what I was getting at.

Fairly good, reasonably accurate, dont exactly give me a warm feeling.
Having worked in a RF lab with 50's era test equipment in the early 60's I 
always had the feeling that accuracy wasnt that great in our SA, calibration 
and readings. EVERYTHING drifted back then which some here dont realize. We 
were barely out of the dark ages. The SA alone was a rack mounted monster 
with a "zillion" tubes that seemed to be getting repaired as much as it was 
used.

I never said that the 4CX250 was a bad tube, just that it has often been run 
by hams at less than desirable levels for SSB which it was never designed 
for back in the 40's. Ian stressed this a decade ago on here and the VHF 
reflector. It particularly irked him since Europe is compact and poor 
signals easily crossed boundaries.

Carl
KM1H