Question: How does the internal balun in a link coupled tuner
compare with the a 'tri-filer' balun such as used in the
Nye-Viking MB-V-A?
Thanks,
73 de Phil - N8PS
---
Quoting "Dr. Gerald N. Johnson" <geraldj@weather.net>:
>
>
> 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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