On Mon, 2009-12-28 at 09:29 -0500, Joel R. Hallas wrote:
> I can't think of a reason that they wouldn't. In fact it is even more
> important with a T match, since there are an infinite number of combinations
> that can provide a match. The point is that the wire in inductors has
> resistance that contributes to loss, while an air dielectric capacitor has
> much less loss. Thus less inductance generally means less loss, all else
> being equal.
Its not that simple. Going to lower inductance and higher capacitance
nearly always means going to a higher loaded Q and that means greater
circulating current to heat the coil and so can raise the loss. This is
also detected by the tuned bandwidth being narrower.
>
> Someone mentioned that measuring the output is an even better way to be sure
> you have the best settings. While they suggested a wattmeter (the
> calibration will not be meaningful since it is not a 50 ohm system at the
> output of the tuner), a better choice might be a relative current indicator
> such as the simple one described in the Sept 09 QST article by Paul Danzer,
> N1II.
Actually the wattmeter is a better relative measure than the ammeter and
has less frequency sensitivity than the ammeter whose indication is very
sensitive to frequency because the current distribution on the high SWR
feed line changes a lot with frequency. Though a poor quality wattmeter
will also show that sensitivity to position along the line.
> MFC also offers an RF ammeter, and there used to be many at hamfests
> from WW2 equipment. Using a transformer to couple to a pilot bulb can also
> work, and doesn't steal much power. If you have a balanced output, having 2
> meters or transformers will allow you to check balance as well.
>
> It's also worth reading the article "Keeping Current with Antenna
> Performance," by Eric Nichols in Feb 09 QST. He actually proposes the idea
> of not worrying about the match between the tuner and radio as you maximize
> tuner output, although that does have some risks.
>
> Regards, Joel
> Joel R. Hallas, W1ZR
>
The beauty of an ammeter is its simplicity, and a small pilot light
(classically it would have been a #48 2 volts 60 ma) with leads tapped a
few inches apart on the open wire line will give a relative indication
though without other apparatus to compare brilliance its hard to compare
intensity from one setting of the tuner to another.
73, Jerry, K0CQ
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