[Elecraft] Magnetic Loops

[Dave Sergeant]

Mike Underhill G3LHZ had some good ideas but his ideas that the 
theoretical loop equations were not valid were totally wrong. When I 
was active on 136kHz some years ago I used a large vertical loop and 
got reasonable results - in a QTH where I was severely restricted in 
what I could use on those frequencies. At one time I more or less 
proved to myself that the loop was performing pretty much how the 
theory predicted and G3LHZ's suggestions that it should be 100 times 
better (or whatever) were complete rubbish. You can find more 
information on the 136kHz pages on my website, with calculations on 
both the traditional loop equations and G3LHZ's (very old pages, not 
updated for yonks, but for some reason still seem the most visited 
pages on the whole site...).

73 Dave G3YMC

On 4 Aug 2009 at 21:57, d.cutter at ntlworld.com wrote:

> I went to one of those lectures by Prof Mike Underhill (G3L??) in front
> of his IEE peers who did not receive his wisdom too readily.  It seemed
> like a one-man campaign.  In essence he postulated that a mag loop was
> more like a short folded dipole and he showed why.  The usual calculated
> losses were insufficient to show why loops worked the way they did.
> 
> I once made a loop from 12ft x 4ft sheet aluminium with a huge capacitor
> 4ft x 6inch vanes spot welded to the ends (that was an education in
> itself).  It was incredibly impractical, but I did it anyway.  I
> measured a 46dB front to side attenuation.  I scrapped it soon
> afterward.
> 
> David
> G3UNA


http://www.davesergeant.com