On Fri, 2008-04-11 at 15:37 -0500, Rob Atkinson wrote:
> As someone else wrote, take a look at the Rich Measures article.
> http://www.somis.org/bbat.html
>
> The price of the Palstar isn't too bad for what you get; I think it's around
> the price of a new 238B. But you can make one--it's not too difficult to
> do, especially if you don't need a lot of power handling capability. I
> don't think the MFJ parallel wire feedline tuner is what I consider a
> genuine balanced tuner. I took a look at the schematic of it when it came
> out and I recall not liking what I saw, but can't recall the details. Don't
> hold me to this but I think it involved 2 or 3 caps and a switched tap
> inductor in some scheme that might transform the balanced Z to 50 ohms, but
> wasn't balanced itself. OTOH, it might work FB for ur power levels. BTW,
> MFJ may have come out with better models since then. I would consider the
> homebrew route myself.
>
> 73
>
> rob / k5uj
Other than by testing for stray capacitance to ground from each side of
the floating tuner I don't think you can detect the unbalance of a
floating single ended tuner compared to a physically balanced tuner.
Each will tune the balanced antenna to a perfect match through the input
balun and that is the best place for the balun because then it sees a
balanced 200 ohm (presuming its the standard 1:4 balun transformer) load
and once tuned is always a perfectly resistive load. No reactance to
tune the balun to resonance and no escalating voltages or currents to
run the balun outside the loads its designed to work with that might
saturate its core.
73, Jerry, K0CQ
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