FW: [ICOM] PW-1/Receiving Antenna Problem

[Adam Farson]

Hi Mike,

The forwarded message shown below may shed some additional light on the
problem. Apparently the RF entering the IC-756Pro2 from the Beverage antenna
whilst transmitting at high power causes an internal EMC issue with the
transmitter ALC circuit. You may be able to verify this by selecting the ALC
meter scale. If the ALC meter deflects well above centre scale when the
problem arises, that may be a cure.

The KD9SV "Front End Saver" offers a definitive fix. Alternatively, you
could rig up an external relay to ground the Beverage input whilst
transmitting.

http://www.radio-ware.com/frontends.htm

Incidentally, if ANT 2/R is selected, the Pro2 will still receive via an
antenna connected to the RX ANT jack, even though the PW-1 input is
connected to ANT 1. The signal-steering relays in the front end will connect
the RX ANT jack to the RF-stage input when either ANT1/R or ANT2/R is
selected.



Forwarded on behalf of Mark Pride/Bedford/IBM at IBMUS
[mailto:mpride at us.ibm.com]
Subject: RE: [ICOM] PW-1/Receiving Antenna Problem 

I recently experienced a similar situation. In my case, when the amp was
keyed, it caused the drive to back off (within a ms. or so) to cause no
input to the amp, which in turn caused no output with the amp. I found the
RF coming down the beverage line caused a kind of AGC action that shut down
the output of the Icom 756 Pro ll. I added a "receiver saver" in line with
the beverage coax and that fixed the problem. Now full power, regardless of
whether I have the 1/R on or just the Ant 1 selected. You need to protect
the front end of the radio from RF coming down the beverage line.

Regards,

Mark, K1RX



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