38S diode thump mod update


From: Steve Miller (kg7pv@teleport.com)
Date: Sun Jun 01 1997 - 10:47:13 EDT

Hi all,
I posted a mod adding back to back diodes to pins 1/2 of the 5532 ( U5).
Had a comment back that this second set ( I had already added diodes to the
first section of U5 pins 7/8) would affect the audio.

Glen was right. On more extensive testing with the second set of diodes I
found that the audio IS reduced on loud sigs. On VERY loud sigs there is
some distortion but that can be dealt with by reducing the rf gain pot. My
first set of diodes took my thump down by 50% and the second set took it
down to a non-objectionable tick.

I have R24 installed and I am using a very efficient pair of 8 ohm Yaesu
phones. Glen noted that for some phones the audio would be reduced too
much by the second set of diodes. My rig has plenty of audio so the gain
reduction is not a concern - works like a simple agc in fact but am not
sure I can live with having to ride the rf gain to deal with distortion on
the very loud sigs. There is not any noticeable audio reduction on normal
or weak sigs that I can hear ... so the usual caution...you mileage may
vary. 73

Steve Miller kg7pv @ teleport.com Portland, OR
(CN-85) Norcal #308 QRP-L #109 ARCI # 9230

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