http://elecraft.85.s1.nabble.com/K3-power-reduction-due-to-high-SWR-tp7439053p7441372.html
The efficiency of the T-network can be less than the Matchbox-type tuner or an L-network
because it is possible to find a suboptimal combination of component values that will give
you a 1:1 match. I believe that the most efficient match is achieved when the T inductance
This can require large values of capacitance in the T network for the lower bands. In my
case both input and output capacitors have maximum values of 600 pf. That is probably not
The impedance range within which the T is efficient depends on the minimum and maximum
values of inductance and capacity that you can achieve. Using a pair of vacuum caps would
be best, but would be VERY hard to tune if you didn't know where to set them first!
I think the Tentec 229 tuner is an L network. It is as efficient as it can be when it is
adjusted for a 1:1 match. I don't know why you got better results with your balun than
> One related question, when speaking of the efficiency of a balanced feedline + balun and
> tuner, what would be a best/worst case scenario for the loss introduced by the
> balun+tuner? Would loss vary significantly by frequency for a nonresonant antenna? I'm
> trying to develop an intuition about the lossiness of the tuner+balun compared to, say,
> 50' of RG213.
>
> I've opted to use a 1:1 balun at the end of 450 ohm ladder line, then a short length of
> coax into a TenTec 229 tuner. In the informal test that I performed, the homebrew 1:1
> balun + coax jumper improved the performance of the antenna compared with connecting it
> directly to the balanced line connectors on the back of the tuner.
>
> 73,
> Matt NQ6N
>
>
>
> On Thu, Apr 5, 2012 at 12:23 PM, Don Wilhelm <
[hidden email]
> <mailto:
[hidden email]>> 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!