[BC] AM transmitter lightning sensitivity issue

[Gregory Muir]

That is a fairly straightforward approach but I would be a little wary about 
the integrity of my very expensive oscilloscope should the tower take a 
direct lightning hit in the process.  A 5KV cap would quickly become either 
a straight wire or a cherry bomb.  The scope?  Well...

When working on radar systems I would always either utilize either magnetic 
coupling or fairly sophisticated voltage dividers depending upon what was 
being looked at in the pulse forming networks.  It was general practice to 
never let the scope get any nearer to the circuitry as possible.  I had to 
justify my test equipment purchases very rigorously.

Greg


----- Original Message ----- 
From: "R A Meuser" <rameuser at ieee.org>
To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
Sent: Thursday, May 22, 2008 12:05 PM
Subject: Re: [BC] AM transmitter lightning sensitivity issue


> Gregory Muir wrote:
>
>>
>> I'm not disregarding the suggestions that all of you have offered.  I 
>> have noted them.  Being from an analytical background, my mind is working 
>> on how to implement a simple instrumentation system to see what is 
>> happening when these events occur.  Power lines have alread been address 
>> using line analyzers.  It became fairly obvious that storms miles distant 
>> had little or no effect on line transients.  The same applied to ground 
>> differentials.  So my attention has turned to the RF side of life.  I 
>> know it is always difficult to look for fast transient events on an 
>> active transmission line so am leaning towards disconnecting the meter 
>> from the base current metering transformer in the TU and connecting its 
>> output to a scope to see if anything can be observed.
>
> Just get a digital storage scope and put in a fairly small value cap to 
> sample the RF. A 100 pf dorknob at about 5KV or higher should be enough. 
> If you want to drop the voltage, add an appropriate value resistor to 
> ground from the cold side. Let the scope run until an event happens. Many 
> write to a PC so you could store scans periodically for better analysis.