Re: [IRCA] IRCA Loop update

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

> I am having a hard time believing that the miniscule
> amount of current flow in the skin of the copper
> pipe, due to received signals, is resistively affected
> by reducing the diameter of the pipe. So, what would
> be the effect of going to 1/2 inch dia pipe, then 1/4
> inch dia pipe? You must reach a point where the
> mechanical instability gets so great that the antenna
> becomes physically unusable, but is the RF
> performance still good enough at these diameters?

I think copper surface area does have a bearing.  In audio, a hum can be
reduced x db by grounding with a #22 wire.  However, often the hum can be
reduced greater by using a #14 wire.  The surface area of a 2" strap at a
transmitter site is often not enough, so a 3" or even 4" is used.

> What would happen if the antenna was made from
> semi-rigid copper strap mounted to an X-frame?
> (besides probably costing more..) Or to a box frame
> with X-shaped supports? Could the antenna be
> made from 4 straight sections designed to be
> attached at the corners, then made transportable
> in some sort of oversized fishing-pole-type
> carry bag? (That's probably over-kill, but an
> interesting thought anyhow. You'd need a
> really rigid corner attachment mechanism)

Low ohmic resistance at the joints would be important.

> What about using a length of 1-5/8 inch heliax
> arranged in a circle and using the corrugated shield
> as the pickup? Too heavy? How would use of a circle
> instead of a square affect the nulling ability?

Even 3 1/8" coax could work, if you could get a toroid over it.  I don't
thing circle vs. square configuration matters.  Putting it as a square or as
a diab=mond with a corner up has no effect.

Craig Healy
Providence, RI


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