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Re: amsat-bb] Icom AG25 mod



Jerry; 
Can you explain exactly what you want to do? Is this a receive only application? If so, all you need is a bias "T" with a switch. I think SSB Electronics has a ready made bias "T" that will work. If it is connected to a transceiver (what model?), then you need a sequencer (included in many radios) to prevent damage when switching between TX and RX. You need to describe your system.

In my case, I use with an Icom IC-970A which has a built in sequencer. I also have an outboard VHF Mirage amplifier. To preserve the sequencer functionality, I had to wire up a dual bias "T" arrangement to extract the bias from the radio and bypass the preamp bias past the output of the Mirage amplifier (the VHF Mirage amp has no DC continuity in RX mode) to a second bias "T". I included a DC relay and driver to sense that the Mirage amplifier was truly off before restoring bias to the AG-25. For the UHF side, my UHF Mirage amplifier passes DC through its internal relay so the AG-35 operates properly without this modification.

Joe

Message: 2
Date: Tue, 13 Dec 2005 11:44:00 -0700
From: Jerry Clement <stormchaser@shaw.ca>
Subject: [amsat-bb] Icom AG25 mod

Does anyone have a mod to enable switching the Icom AG25 preamp on & off  with a external switch. thanks
Jerry VE6AB
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