[TenTec] 4229 Tuner Balun Replacement?

[Steve Hunt]

Of course, the Johnson Matchbox has its secondary capacitors 
"centre-tapped" to ground; that makes it a "stiff" voltage source. In 
other words it's a VOLTAGE balun, just like the 4:1 Ruthroff found as 
standard in many tuners. But usually we want to balance the currents in 
the TL, not the voltages on each leg.

That referenced 1:1 balun from Balun Designs is a good choice - 
particularly for the lower-frequency bands.

73,
Steve G3TXQ

On 14/11/2010 03:59, Ken Brown 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?
>>
> A link coupled tuner IS a balun. It is not a tuner WITH a balun. It is
> essentially a tunable air core transformer. Usually (perhaps always) a
> link coil of just a few turns is the primary of the transformer, fed by
> the UNbalanced transmission line (coax) from the source (transmitter).
> The secondary generally has a many turns, perhaps tapped for band
> switching (as in the case of a Johnsom Matchbox) and is connected to the
> BALanced transmission line to the load (antenna). The transformer
> windings have variable capacitors connected to them to make it tunable.
> In the Johnson Matchbox only the secondary has tuning capacitors. Other
> variations may also have a tunable primary. In the Johnson Matchbox the
> secondary is actually two coils, with the primary link in the middle of
> them.  Or perhaps you could say it is one big center tapped coil, with
> bandswitching taps at both ends.
>
> My labeling of primary and secondary assumes that you are transmitting.
> Turn the labels around for receiving.
>
> DE N6KB
>
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