# [Fwd: LF: Yet more loops]

**André Kesteloot**
akestelo@bellatlantic.net

*Mon, 15 Jun 1998 10:17:28 -0400*

Peter Martinez wrote:
>* >From Peter Martinez G3PLX Kendal Cumbria.
*>*
*>* After my last about multi-turn versus single-turn loops, I realised that
*>* there is another more interesting question worth answering: Given
*>* that I have a fixed amount of copper, is it better to make a large loop
*>* of thin wire or a small loop of thick/parallel wires?
*>*
*>* Since we now know that it doesn't matter whether we connect wires
*>* in series or parallel in a loop of a given size, I think this question can
*>* still be answered with thought alone. Suppose I have paid a pound at
*>* a boot sale in Canterbury and bought 100m of wire. I feed 1 amp of
*>* RF into it and keep this constant throughout the next part of the
*>* experiment. The power loss heating the wire (assuming it is much
*>* greater than the radiated power) will be constant during the next
*>* paragraph.
*>*
*>* I now coil it, first as a square loop of one turn, which will have a side
*>* of length 25m and hence an area of 25^2, and hence a radiation
*>* resistance of K*25^4, where K=320*pi^4/L^4. The radiated power will
*>* be I squared times this, that is K*25^4 since I=1.
*>*
*>* Next I coil it as a two-turn loop, which will have a side of 12.5m and
*>* hence an area of 12.5^2 and an Rrad of K*12.5^4. Remembering that
*>* 2 turns of 1 amp is the same as 1 turn of 2 amps, the radiated
*>* power is 2-squared times K times 12.5^4. (You get the same result
*>* if you do it Andy's way)
*>*
*>* The radiated power of the single-turn loop is thus 4 times higher than
*>* that of the 2-turn loop WITH THE SAME WIRE AND THE SAME
*>* TRANSMITTER POWER. It therefore seems to be best to build the
*>* quantity of wire that you have into the largest single-turn loop that
*>* you can get into your space.
*>*
*>* 73
*>* Peter
*