[BC] Platinum-Z problem

[Broadcast List USER]

Checking the line and antenna with a TDR is a good first step, buy  
you also need to use a network analyzer to ensure things look right  
over the entire line and antenna.

Also, there is a real difference in TDRs -- from Yugo to Lamborghini  
Countach.  There is some real crap out there that won't find  
anything, and will mislead.

VISUALLY INSPECTED?  Unless the problem is very serious, you are not  
going to find anything visually.  If the line is holding pressure, it  
is very unlikely you will be able to SEE any problems.

On Feb 27, 2009, at 6:00 AM, broadcast-request at radiolists.net wrote:

> Message: 5
> From: Allen Sherrill <warp99 at hotmail.com>
>
> We are getting ready to help out one of the local non-coms with an  
> intermittent foldback or muting problem on a Harris Platinum-Z10  
> (analog, no HD).  Several times a day the exciter is apparently  
> muting.  The fault indications seem to be VSWR trips.  The problem  
> occurs at any power level above about a kilowatt.  Station  
> frequency is 88.1.
>
> The contract engineer does not suspect an actual VSWR problem,  
> although it can't be ruled out.  The antenna and transmission line  
> (approximately 100' of 1 5/8") have been visually inspected  
> (externally) and appear fine.  The line is holding pressure with no  
> problems and has been pressurized since installation.  I'm going to  
> suggest he get a TDR and make sure it's OK, and get a tower guy to  
> check the antenna fitting.
>
> The contract guy has swapped in a different exciter (Digit) and  
> changed controller/life support boards in the Z, and the problem  
> persists.  If it's not an actual VSWR trip I might suspect RF  
> getting into the ribbon cables between the exciter and the Z  
> controller.
>
> Allen Sherrill