Ron E. Schuster wrote:
> I am running a beverage antenna on 160 to receive. I am plugging it into
> the RX IN jack. Only when I have the RX antenna ON and am using an AL-80A
> linear, I get a moderate feedback/oscillation in the linear. Anyone have
> any ideas?
Hi,I have found that the 990 ALC is affected when using the RX input with high
power nearby. Put about 4 (2 pairs) 1N914 or 1N916 diodes reversed from each
other across the RX input (input to gnd). The diodes are in parallel and
reversed from each other (one up, one down) so as to limit the voltage picked
up by the RX antenna to about 5 volts pp or less (the diodes rf impedance is
higher than you would think so the rf voltage across them exceeds the 0.7
volts that you might expect). I found that with about 15 volts pp or so, the
ALC was affected (turned off, resulting in max output in my caseo). The RX
input goes to the same board that has the ALC circuitry. The more pairs of
reversed diodes you use, all in parallel, the more attenuation you have with
diminishing returns. Two pairs should be just fine.
You can also use an external relay, but this diode thing works fine for me.
--
Charles (Jack) Hawley
Chuck....Ham Radio KE9UW
AKA "Jack" BMW Motorcycles, MOA #224 K100RS
Wife rides...Viki, MOA #18120 K100RS
President IBMWR
c-hawley@uiuc.edu
Sr. Research Engineer Emeritus
University of Illinois, Urbana-Champaign
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