[amsat-bb] Re: Icom AG-35 Preamp Question

12 Aug 2012

      Hi All,
Somebody please clarify---I may be wrong, but I thought the Icom preamps did the following with Icom radios:
In receive, 12V is powered up the coax.  Device is powered, preamp is ON.
In transmit, the 12 power feed is stopped. Device is not powered, and it's bypassed during xmit.
If this is the case, it complicates greatly the use of Icom preamps on non-Icom radios (means there isn't a typical RF-sensed bypass circuit, which means it would be easy to blow in a non-Icom radio).
Am I remembering this wrong?
Mark N8MH
At 09:30 PM 8/11/2012 -0700, Art McBride wrote:
...
Rick,
I suggest you use a VOM or DMM to measure the current drawn on 12 volts
going to the power injector. If everything is connected correctly It will
draw 30-200 mA. Confirm that you have continuity in your coax. Some
lightning arrestors have a DC block built in. It is best to test it with a
short run of coax between the preamp and the power injector at the radio
while listening to a local repeater to see if the signal increases when you
apply power to it. If it operates then you can proceed to determine if there
are problems with the coax to the antenna, not carrying the 12 VDC. 
73
Art,
KC6UQH
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Lawn, Richard
Sent: Saturday, August 11, 2012 3:30 PM
To: [email protected]
Subject: [amsat-bb] Icom AG-35 Preamp Question
I bought an Icom AG-35 preamp about a year ago. The fellow ham advertised it
as virtually brand new and it was/is. I planned to use it this summer with a
TS-2000 which doesn't supply 12v voltage to the coax to power a preamp as
other xcvrs do. I used a Mirage KP2 unit to inject power to the coax to
drive mast mounted the preamp. When I turn the power on there seems to be
little or no noticeable difference in background noise and worse than that I
cannot here any signals on FO-29 downlink, and I know the bird has been
active. Any suggestions? Is the preamp fried? I can't even get the weather
proof case off to trouble shoot, not that I'd know what to look for. Any
suggestions on repair?
TNX
73
Rick
W2JAZ

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[amsat-bb] Re: Icom AG-35 Preamp Question

Mark L. Hammond