There is NONE. The output coil is balanced to ground, as are the
capacitors, which in my link coupled tuner can be switched from parallel
for high impedance loads to series for low impedance loads. The balance
is in an air wound coil, no ferrite or powdered iron involved. The link
can be variable coupling or use a series capacitor to adjust the
impedance match after the tuned output coil resonates the antenna and
feed line. Or better to say it supplies reactance to make the circuit
resonant at that point.
73, Jerry, K0CQ
On 11/13/2010 8:25 PM, Phil Sussman wrote:
> 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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>
>
>
>
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