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@gmail.com>
To: towertalk <towertalk@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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