[Amps] Bandwidth tests

[Joe Isabella]

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 at w8ji.com>
To: Joe Isabella <n3ji at yahoo.com>; Michael Tope <W4EF at dellroy.com>; g3rzp at g3rzp.wanadoo.co.uk; zdtech <zdtech at iprimus.com.au>; amps at 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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