Re: K3 power reduction due to high SWR
Posted by
Vic Rosenthal on
Apr 05, 2012; 8:34pm
URL: http://elecraft.85.s1.nabble.com/K3-power-reduction-due-to-high-SWR-tp7439053p7441370.html
All the tests -- signal comparison and noise tests -- were done on the same band, to which
the tuner was tuned (40m).
On 4/5/2012 12:23 PM, Don Wilhelm wrote:
> 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!
>>
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/______________________________________________________________
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