Re: K3 power reduction due to high SWR
Posted by
Don Wilhelm-4 on
Apr 05, 2012; 7:23pm
URL: http://elecraft.85.s1.nabble.com/K3-power-reduction-due-to-high-SWR-tp7439053p7441138.html
Vic,
Where was the frequency of the GDO with respect to the band the tuner
was set to? If it was below the band of interest, I would expect
something like that - the T-Network is a high pass filter.
73,
Don W3FPR
On 4/5/2012 12:28 PM, Vic K2VCO wrote:
> Speaking of balanced lines and tuners, I recently did an experiment that surprised me.
>
> I have a dipole fed with 600-ohm open-wire line (and some window line indoors). I usually
> tune it with a Johnson Matchbox, a fully balanced link-coupled tuner.
>
> I was lucky enough to get my hands on a massive, high-quality edge-wound rotary inductor
> in a well-made aluminum enclosure. So I built a high-power T-network tuner with it. I
> purchased a good (and expensive) 1:1 balun designed for use after a tuner from DX
> Engineering, and compared the T-net + balun to the Matchbox. I didn't notice any
> difference in the strength of received signals between the tuners.
>
> But here is the surprising part: I expected that the Matchbox would provide better
> balance, which would reduce radiation and pickup from the feedline. To test this, I
> coupled a grid-dip oscillator to the feedline about 20 feet from the tuner.
>
> To my great surprise, the signal from the oscillator was much weaker with the T-network +
> balun than with the Matchbox!
>
> Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners!
>
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