GM Steve,
The problem that we are fighting is common mode current . . . which rises when
the antenna is closer to the ground (electrically).
In all of the tests that I have run on dipoles and OCFD antennas, the lower
bands, being electrically closer to the ground, have significantly more problem
with CMC than the higher bands.
Therefore I chose to run with #43 when 80m is required.
I agree the point of using bifilar.
I'm just to lazy to make it, and Teflon coax is readily available here.
The Model 1161 looks nice and the price is right, but I would prefer to have 2
or 3 more turns on it for the reason stated above.
I am also uncomfortable with its 5kW rating!
However for OM who cannot or do not want to home-brew, it is a good alternative.
73,
Rick, DJ0IP
(Nr. Frankfurt, Germany)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Steve Hunt
Sent: 28 December 2017 11:19
To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] 238 "Tuner" Balun
As others have said, the internal balun is a 4:1 voltage design - a better
option is a 1:1 current balun.
I use my TT238 tuner with an external 1:1 current balun comprising 11 turns on
two stacked FT240-52 cores. CM performance charted here:
http://www.karinya.net/g3txq/temp/52_mix.png
Type 43 material would be better for the lower frequency bands, or Type
31 if you're trying to cover down to 160m. Performance charts are here:
http://www.karinya.net/g3txq/chokes/
with some more extensive data here:
http://www.karinya.net/g3txq/chokes/type31.jpg
http://www.karinya.net/g3txq/chokes/type43.jpg
http://www.karinya.net/g3txq/chokes/type52.jpg
The winding doesn't need to be coax because we typically are not trying to
preserve a 50Ohm impedance through the balun. Using bifilar windings with PTFE
insulation will provide a higher voltage withstand capability.
Balun Designs has a model similar to the one I am using:
http://www.balundesigns.com/model-1161-1-1-atu-current-balun-3-54-mhz-5kw/
Steve G3TXQ
On 28/12/2017 02:10, Bob Good wrote:
> The Ten Tec manual has virtually nothing to describe the internal
> balun supplied with the unit. I do not know how to physically look to
> tell its design. Is it a 1 to 1 or a 4 to 1; Current or Voltage
> design? Okay, if it is 4:1 or voltage design, please comment on the
> proper design in schematic form or picture; what ever it takes for me
> to wind a current design, 1 to 1 balun. Can the toroid be reused? I
> use it on a ladder line, center fed 135 ft. dipole up 60 ft. Other
> antennas are coax fed. Thanks to all who would like to help this
> analog old timer. Happy New Year and ‘73. Bob K4BG. (Good on QRZ)
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
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