Re: [Amps] 4CX1500B

[Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>]

Rich said:

>So, do not use a meter that has sticky bearings.

You still have to set it to around 1.5% of full scale.


>The IMD level produced by the transmission of human speech can not be 
found by a 2-tone IMD test. 
Agreed.
I use a steady "ahhhhhhhhh".

A 2 tone test is a convenient start, A 3 tone test with 2 of the tones very 
close - say 20 to 30Hz apart - is useful. That really shows up the power supply 
filter capabiliites. For real reproducability between measurements, modulating 
the tx with noise works pretty well. That was how they used to measure the IMD 
of the old analogue multi channel telephone systems.

73

Peter W6/G3RZP
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