From: G0MRF@aol.com
Message-ID: <b4c82abf.36fe36c5@aol.com>
Date: Sun, 28 Mar 1999 09:03:49 EST
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: TDA2030 as LF PA?
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Hi Johan.

I've used the 2030 as a driver for my linear since I've been on 136k.  As a
benefit it also works well on 73.

I can confirm that it has been "indestructable"  The worst event has been to
latch up under some very extreme RF feedback / Mismatch conditions. Even then
if you turn off the power and then reapply the device returns to normal
operation.

The efficiency is low.  I see 12 Watts out at 24 Volts.   A 78S24 regulator
works well although more power is available at 28V.

I've used the suggested circuit from the data sheet available at the
manufacturers web site.  All signal path electrolytics have been replaced by
smaller values. The most important change was to the Zobel network on the
output.   The series resistor and capacitor to ground were changed to 2.2 Ohms
and 0.047uF.

Finally,  I tried matching the output directly to the linears input impedance
but eventually found a separate 1:9 step up transformer had improved
performance.

73


David.


ps thanks for the new DDS firmware earlier. I have been tied up with work but
have slowly been collecting the parts.