[TowerTalk] choke / balun design needed

[Roger (K8RI) on TT]

A Sloping dipole is certainly unbalanced, but it shouldn't present the 
unbalance on 30 that I get on the 75-80 meter band.  Much does depend on 
the height above ground  It took two hefty chokes to keep the RF out of 
the shack and in the antenna.

The nice thing about the 2.4" toroids is that size allows enough turns 
of RG-8/LMR-400 size coax even for 160, but be warned.  It may take a 
generous helping of wire pulling soap for that last turn or two.  Of 
course if you spend a little more, you can get a bunch of the Teflon 
insulated, silver plated  coax and not worry about weight, or  size.

Choke  http://www.rogerhalstead.com/ham_files/AntennaFeed1.htm
Choke  http://www.rogerhalstead.com/ham_files/AntennaFeed2.htm
Spreader http://www.rogerhalstead.com/ham_files/AntennaSpreader1.htm

Being open like that give plenty of cooling

Even running "the limit" with my long winded transmissions I've never 
noticed them getting hot, nor any change in characteristics on the VNA 
which is sensitive enough to show the effects of the wind on the antenna.

73

Roger (K8RI)

On 4/29/2015 3:19 AM, Jim Thomson wrote:
> Date: Tue, 28 Apr 2015 13:37:35 -0400
> From: Alex Malyava <alex.k2bb at gmail.com>
> To: towertalk <towertalk at contesting.com>
> Subject: Re: [TowerTalk] choke / balun design needed
> Message-ID:
>
> so,
> what do I do for simple inverted vee or sloped dipole?
> 1:1 voltage balun or coax choke?
>
>
> ##  Use a good choke balun.  Use some type-31 cores,
> like the 2.4 inch OD variety....then optimize the choke
> design for the 30m band....  10.1  to 10.15 mhz.
> Since the choke only has to work on one band, it will be easier
> to optimize it for 30m band. K9YC has some excellent cook book
> designs on his tutorial.   An optimized 30m choke, plus the 30m
> dipole, fed with coax, is as good as it gets.  Swr will be dead flat
> since the band is only 50 khz wide.
>
> ##  A sloping dipole will no doubt un balance the entire mess.
> Use the inverted vee configuration.  A 30m dipole is aprx  46 ft long,
> so 23 ft per leg.  End of problem.
>
> Jim   VE7RF
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-- 

73

Roger (K8RI)


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