Re: [IRCA] IRCA Loop update

[Stephen Hawkins <ng0g@xxxxxxxxx>]

Craig,

On Thursday 10 November 2005 22:44, Craig Healy wrote:
> I have to tell you, I don't think I will ever make a wire loop again.  The
> untuned copper loop works better than any tuned wire loop I've ever made or
> used.  It's dead simple to make and simpler to use.  It also seems nearly
> immune to hand capacitance.
snip
> I may make one half this size to see just how small I can go before it
> stops working effectively.  There is remarkably little difference between
> this and the original ten foot loop I built.

I am very puzzled by this.  It seems to me that a copper tubing loop would 
just look like a very thick piece of wire about 8 feet long, or in the case 
of the larger loop you built about 40 feet long.  I learned to make loops 
from Ralph, and the wire loops I built have between 95 and 120 feet of wire.  
It seems to me that all of that extra wire, especially when compared to the 
smaller of the loops you built, would have a much larger "capture area" so to 
speak, when compared to 8 feet of thick wire.

In an electrical generator the current is induced to flow in the wire by 
passing a magnetic field across a coil of wire.  The larger the coil, or the 
stronger the magnetic field, the more current you can generate.  In an 
antenna the magnetic field is replaced by the radio wave from the station.  
The stronger the wave, or the larger the coil of wire, the more current 
should be induced to flow.  So it puzzles me that the 8 foot copper tube 
works as well for you as 90+ feet of wire.  

In some kinds of antennas, like an ordinary dipole, for instance, a wire that 
is very thick can add some usable band width to the antenna.  That is why 
they used to build those "cage" dipoles that were several parallel wires, 
held apart in a kind of circle by spreaders, to form an artificial "thick" 
wire.

Does anyone have any thoughts that might shed some light on this.

Steve
-- 
73 49 111 01001001
Stephen Hawkins NG0G
ng0g@xxxxxxxx

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