On Wed, 2008-07-09 at 06:00 -0700, Jim WA9YSD wrote:
> Some people like but radios cause they look for the one that operates well
> and has a nice feel to it or how it looks or what ever.
> I have gone through 6 different tuners and used a bunch more along with
> home brews over the years and built two of my own. Each one has its own
> feel, looks and operating characteristics. One I built that came out
> of the ARRL Hand Book.
> I do not like one that if you just tap on the knob that adjusts the
> caps the tuning needs to be readjusted. Ground conditions change and
> a daily basis and you need to tweak settings all the time. Roller
> inductors so tight that you need a crank handle to turn it and not
> a figure knob to spin it. Or a roller inductor that when you just
> tap on the knob the tuning needs to be readjusted
A roller inductor depends on pressure of the roller on the coil turns
for that connection. When the pressure is low, the contact gets dirty,
and so gets scratchy while tuning receive or transmit though it shows
first on receive. Stiff roller coils sometimes get that stiffness from
roller pressure (often wedging between coil turns), though they could
just be in need of lubrication of the bearings.
> I like a roller inductor when I spin the dial it moves at least a
> half a turn when I stop.
To me that's too loose tending to get noisy early.
> Some tuners are broad band, while others are narrow. Some have a bit more
> band width
Some of that depends on the tuner circuit, the choice of reactances for
a particular load and some of that depends entirely on the load, a
highly reactive load tends to demand a high loaded Q in the tuner and so
> I have yet to see a consumer tuner sold that indicates or automatically
> finds that SWEET SPOT so you need to do minimal or no tuning at all
> when changing from SSB to CW portion of the band or just changing bands
> when using the same antenna with minimal tuning.
That is quite true of all tuners except the L match. Most auto tuners
are L matches.
> One of the things I like about the Ten-Tec 253 Auto Tuner is that
> it finds the lowest SWR at the proper Q.
> I have not learned how to find the proper minimal SWR at the proper
> Q with a manual tuner. It was all ways trial and error. For the
> most part I start with the caps at mid range, roller inductor 3
> turns off the bottom, and work from there.
IF the receiver works best with a 50 ohm source, one can get a start by
peaking a received signal or just antenna noise. SWR checking with noise
bridge (tuner tuner) or transmitter always seems pickier and ends up
with a tuning a bit away from that received peak.
Probably the optimum insertion loss/wider bandwidth condition on a T
match is the match that uses the greatest inductance and least
capacitance for the lowest loaded Q. Most of stop tuning once we get a
match and don't search for alternatives.
> Keep The Faith, Jim K9TF/WA9YSD
73, Jerry, K0CQ
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