Start off by getting rid of the LMR-400 feedline !! 

Do not use braid over tin foil feedline for repeater duplex operation.
Internal chaffing of braid and tin foil with any feedline movement during
transmit will "kill" your repeater. 

To confirm the problem IS with the feedline swap it out with a 50 foot piece
of LDF-50 or even a piece of good old Beldon 8214 coax.


Ron Rogers
-WB8ERB-

-----Original Message-----
From: sledman11 [mailto:[EMAIL PROTECTED]
Sent: Tuesday, November 11, 2003 1:57 PM
To: [email protected]
Subject: [Repeater-Builder] Static / desense problems


Looking for idea's on tracking down an intermittent static and 
desense problem I am have with a 2 meter repeater.  The set up is as 
follows - ge mastr II base, LMR 400 coax (about 50 ft) into a diamond 
F23A antenna mounted on a chimney with 22' of black pipe mast.  The 
location is the local firehouse which has a antenna mounted on a 
tower about 70' feet away from the repeater antenna.  We also have a 
220 Mhz, 4 element beam mounted on the back pipe mast about 12' under 
the repeater antenna.  This is for echolink.  Have turned off the 220 
Mhz link with no affect on the problem.  Have not been able to 
determine a pattern to the problem (ie cold, wet windy etc).  When it 
happens it can sometimes completely wipe out a signal that was full 
quieting.  Have checked the antenna and all is tight, dry and no 
problems that I can see visually.  Including the coil and capacitor 
at the bottom of the antenna.  Thought about running jumpers between 
the antenna mount, mast, 2 meter antenna and the 220 Mhz antenna so 
all are at ground potential.  Do feel it is something outside that is 
causing the problem and not the radio or duplexers.  Can create 
static on a weak signal coming into the repeater by banging on the 
mast.  All idea's welcome.

Thanks,

Don
WW2N




 

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