[TowerTalk] To get a truly balanced antenna feed

[Edward McCann]

Sent from my iPhone

> On Jun 23, 2016, at 6:27 AM, Edw McCann <edwmccann at aol.com> wrote:
> 
> Any suggestions how to apply this concept to ladder line/open feed? 
> 
> Ed McCann
> AG6CX
> 
> Sent from my iPhone
> 
>> On Jun 23, 2016, at 12:48 AM, Ian White <gm3sek at ifwtech.co.uk> wrote:
>> 
>> 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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