VE7RF wrote:
>## Ian mentions the current. If that’s the case, why not just
>measure the current with a clamp on ammeter.... at say
>several random places on the coax feedline ?
That is exactly what I try to do - see my website: "Clamp-on RF Current Meter -
*the* most useful tool for RF interference troubleshooting."
http://www.ifwtech.co.uk/g3sek/clamp-on/clamp-on.htm
A perfectly functional instrument can be thrown together in half-an-hour. The
passive diode detector will typically read from about 25mA up to 1A. It is also
possible to build a much more sensitive log-scale instrument based on an AD8307
detector chip (or similar) which will read down to 1mA, but with reduced
resolution.
> Then we have yet another issue to deal with, and thats
>what if the coax braid is bonded to the top of the tower ?
>If a lousy CM choke balun is used at the ant feedpoint,
>and braid also bonded to top of tower, we can then have
>a case where CM current is now flowing down the tower.
Well jes' don't do that! Don't use a lousy CM choke at the feedpoint, use a
good one; and if in any doubt, use another CM choke (which doesn't have to be
so good) just above the point where the braid is bonded to the tower.
Or best of all, measure the CM current both before and after.
73 from Ian GM3SEK
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