[TowerTalk] Force 12 B-1/B-1S Baluns

[EZ Rhino]

The wood spacer is a good idea, maybe Jim can chime in on how much spacing is needed.  This is a real problem with double boom log periodics since both booms are hot with RF, and running the coax along the lower boom is obviously counterproductive.  W8JI has some thoughts on this problem on his site, which I followed with some success.  I'm experimenting with different kinds of chokes at the boom/mast junction and trying to find something that is mechanically durable while maintaining the maximum choking impedance possible.

Chris
KF7P



On May 14, 2013, at 15:30 , Brian Alsop wrote:

I just taped the coax coil to a block of oak and tiewrapped/tapped the wood to the boom.

Even worse than this is winding the coax turn on the boom.  The boom ends up being a shorted turn!

The way around all of this is to use a toroidal balun.  More $$ but a much easier and more robust mechanical solution.  Electrically they are more broadbanded and work well with multiband antennas.

73 de Brian/K3KO

On 5/14/2013 20:58, Chris wrote:
> Okay so how do you route the coax back to the mast from the driven element then?  Dangle the coax below the mast?  Add another choke at the mast?  But wait!  The mast is metal too!   Just how much of a problem is this stray C, anyway?
> 
> Chris
> KF7P
> 
> 
> 
> 
> 
> 
> On May 14, 2013, at 2:50 PM, Tom H Childers wrote:
> 
>> 
>> 
>> One reason those folks, which has included me have done that, is
>> because most loaded Yagi-Uda antennas sold by CushCraft and others
>> recommend doing just that in the assembly instructions!
>> 
>> 
>> 
>> 
>> On Tue, 14 May 2013 20:28:54 +0100, "Ian White"
>> <gm3sek at ifwtech.co.uk> wrote:
>> 
>> [snip]
>>>> How many times have you seen a coiled-coax choke taped
>>>> to a boom - think about that in terms of a high-Q parallel tuned circuit!
>>>> 
>>> Not only that, but taping the choke to the boom is adding extra capacitance between one side of the driven element and the boom. In other words, taping the "choke balun" directly to the boom is making the antenna more UNbalanced!  It's amazing to watch people doing this...
>>> 
>>> 
>>> 73 from Ian GM3SEK
>> [snip]
>> 73,
>> Tom
>> Amateur Radio Operator N5GE
>> ARRL Lifetime Member
>> QCWA Lifetime Member
>> 
>> _______________________________________________
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