[amsat-bb] Re: Duplexer / 847 / Preamp Question

Jim Jerzycke kq6ea at pacbell.net
Mon Jul 27 20:56:14 PDT 2009

It should work fine. The only thing to check is that the center conductor of the coax is NOT at DC ground. That will blow the trransistor used to switch the DC on or off in the menu.
I blew mine this year at Field Day on the 2M side. I had it connected to a multisection helical filter, and didn't check before I powered up the radio.
I'm going to run a separate power lead for the preamps from now on! 
DC up the coax is nice until you do something stupid like I did.
73, Jim  KQ6EA

--- On Mon, 7/27/09, harry at gunship.org <harry at gunship.org> wrote:

From: harry at gunship.org <harry at gunship.org>
Subject: [amsat-bb]  Duplexer / 847 / Preamp Question
To: "AMSAT" <amsat-bb at amsat.org>
Date: Monday, July 27, 2009, 7:57 PM

I want to use an FT-847 with a mast mounted SSB preamp and a single feedline antenna (Cushcraft A270-10S) that I already have mounted on my tower.
Can I send the DC for the preamp up through the coax and still use a duplexer?
I have checked the continuity of a Comet CF-4160 duplexer and the 1.3-170MHz side appears to be isolated from the 440 side.  Since there is direct continuity on the 1.3-170MHz side of the duplexer I would run the DC for the preamp up that "side."
I really don't want to blow up my 847 by doing something foolish so any thoughts, cautions etc. welcomed.
73 de harry, W6DXO

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