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Re: [TenTec] 4229 Tuner Balun Replacement?

To: tentec@contesting.com
Subject: Re: [TenTec] 4229 Tuner Balun Replacement?
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Reply-to: geraldj@weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sat, 13 Nov 2010 18:23:18 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>

On 11/13/2010 11:21 AM, Jim Brown wrote:
> On 11/12/2010 4:22 PM, Stuart Rohre wrote:
>> Most external baluns are of heavier construction and therefore lower
>> loss potentially, than built in baluns common to 1970's tuner designs.
>
> Loss in ferrite chokes and in baluns wound with ferrites is NOT a
> function of HEAVY construction, but depends primarily on the
> characteristics of the ferrite material (the MIX),  how the chokes are
> wound (mostly the number of turns), and the size of the core.

The LF end of the useful range depends on the raw inductance of the 
winding which comes from the magnetic material and the turns. The first 
stop band going up is when the length of the wire (loaded by dielectric 
of the insulation and the core) gets close to 1/2 wavelength. Going to a 
bigger core adds more wire per turn and tends to lower that HF end. Its 
easiest with a tiny core to get the broadest bandwidth, like the cores 
in a TV splitter that work from 10 to 1000 MHz (and cost $2.98 retail 
assembled).
>
> Likewise, HEATING in the core depends on the loss, the TX power level,
> the balance of the antenna, AND the length of the transmission line into
> which it is inserted.  Using a balun on Field Day (usually 100W) and
> saying it worked fine doesn't mean much. A FAR better test would be
> running 1.5kW through it into difficult lengths of line and with an
> unbalanced antenna (like a Windom) and noting whether or not it got hot.

True. I remember a balun the antenna boys at Collins built and had us 
test with 50 KW from our 250KW VOA transmitter we were developing. The 
first try smashed the core. They had to redesign for better cooling a 
couple times.
>
> Although I own and love a half dozen Ten Tec tuners, I don't use
> twinlead, so I've never given the balun a torture test. :)

I prefer a link coupled tuner with balanced output, the I don't have the 
limitations of the balun on the tuned side.

73, Jerry, K0CQ
>
> 73, Jim K9YC
> _______________________________________________
>
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