That's what I was able to see, Tom. The IM products were much stronger with
white noise & max ALC than with speech & no ALC or even speech with ALC. I did
*NOT* do very comprehensive testing, in the lab, so I'm borrowing an HP spec
any tomorrow to do some more detailed testing. What tones should I use? I
read the section on your site about injecting a "warbling" tone a while back --
I believe that was at 100 Hz (??). Given my audio bandpass is roughly 20Hz to
4kHz @ -6dB, I can do some pretty interesting testing.
I'll post the results as real-time as I can...
Joe, N3JI
----- Original Message ----
From: Tom W8JI <w8ji@w8ji.com>
To: Joe Isabella <n3ji@yahoo.com>; Michael Tope <W4EF@dellroy.com>;
g3rzp@g3rzp.wanadoo.co.uk; zdtech <zdtech@iprimus.com.au>; amps@contesting.com
Sent: Monday, July 3, 2006 4:24:04 PM
Subject: [Amps] Bandwidth tests
> White noise is definitely worst-case, and with max allowed
> ALC it makes an ugly spectral plot.
That's not true at all!
Steady white noise is NOT a good test of dynamics of bias or
ALC systems. As a matter of fact, it is the poorest test
available for determining bandwidth problems related to poor
power supply dynamics, poor ALC dynamics, and other similar
problems.
ALC testing requires a three-tone or pulsed two-tone or
noise test at various pulse repetition rates. Amplifier IM
products related to typical screen or bias system dynamic
regulation shortfalls NEVER show in a steady white noise
test.
If I wanted to use a test that masks bad power supply
dynamics or ALC attack problems and make the system look
significantly better than it does on voice, it would be a
white noise test.
73 Tom
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