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Re: Topband: Shunt feeding the Skyneedle - new developments

To: "Carl Braun" <Carl.Braun@lairdtech.com>, "'160'" <topband@contesting.com>
Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
From: "Tom W8JI" <w8ji@w8ji.com>
Reply-to: Tom W8JI <w8ji@w8ji.com>
Date: Sat, 22 Feb 2014 09:09:27 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Thanks for the tip. I may play with a bit of inductance just to see how the system reacts. >>>

This is way more problematic than it needs to be.

First, no one even knows if the reactance is real or a false reading caused by a bit error from calibration or noise.

Second, no one knows the sign of the reactance if it is there. It might be already be inductive.

Third, if the capacitor is not maxed out or at minimum and still has range left, which yours does, the capacitor will adjust out any reactance without adding anything else.

There are certain bridge voltages that with even one or two bits error, which is 2/256 bits or less than 1% error in voltages, where 10 ohms might be calculated. The algoryth tries to take that error out by watching SWR near bridge balance instead of bridge arm voltages, but I have no idea how the unit is calibrated or if the antenna system has noise causing a bit error.

All of this is pretty much meaningless. Even if it is a 1.3 :1 SWR, it is not going to be a problem. Also, if the real part is near 40 ohms and you have a high Q antenna system and losses, you might find lowest SWR is not X=0 because of interactions between resistance and reactance as things are tuned.

I would not even guess at a cure for something with a bunch of unknowns that might not even be a problem. I think this is a bigger worry and more complex than it should be.

73 Tom
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