Patti <pthielking@earthlink.net> wrote:
I am looking for some hint's regarding a lack of ALC operation on an OMNI
D. Anyone willing to help, can contact me off-list.
Thanks
Eric Thielking
Do you have the manual? The OMNI-D manual is very extensive for
troubleshooting and aligning the radio.
On the board that has the reed relay for the antenna TX/RX Switch, ( sorry
this is from memory here), there are some diodes, the board is in the metal
box near the RF Connector. You may have to unsolder the diodes to test
them, or just plan to replace them anyway with good diodes.
These diodes go out often, especially after a near by lightning strike with
the antenna connected. simple to replace the diodes. They have a number of
functions depending on the position of the reed relay. A pair prevents the
antenna voltage from going too high on receive thus usually protecting the
RF Amp transistor, another pair feeds the SWR meter during transmit and
also sends the amount of SWR back to the ALC Board to fold back the power if
the SWR is high. did I miss anything? there is a control to set the SWR
detection and this should be aligned.
If that is all ok, then check the inputs on the ALC Board. there is a
control there to adjust the amount of fold back.
To align the SWR meter, you will need to connect three dummy loads in
parrallel. ( three in parralell will get you a 2:1 or 3:1, It's in the
manual ). the pot to adjust this is on the same board with the receiver
protect and SWR detect diodes. Once the SWR is reading correctly, then go
to the an ALC adjustment, and a single dummy and adjust this for the full
100 watts out, ( with drive and alc controls set correctly too ) . You
may have to open up the ALC control first to set the SWR, don't go over 90
to 100 watts...
If everything is working, it should line out for you.
Best wishes,
Rich
K5SF
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