[Lowfer] LF Lop Antennas

[Peter Barick]

Hi Tom,

I agree w/ John A. as to:
... given the low noise in electronics at LF, and the high noise in the environment, a 
high Q circuit may improve the signal, but not the signal to noise 
ratio, unless the antenna BW is narrower than the rest of the system.
 -- John Andrews, W1TAG
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I looked at the supplied url and a few of the links, interesting. But I observed an error in the narrative on the first one, pertaining the directivity of a tuned loop antenna. The first diagram is correct, showing it in the plane of the loop, that's max signal. However, the next one (for a spiral winding) is incorrect. It should be the same as the first as it occupies a like plane.

Here are some seat-of-the-pants hints for a receiving loop. Starters:
1) Don't worry about "special wire," small gauge anything is okay: CU, AL, yes, Fe. Uninsulated or not (on dry spreaders!)
2) A simple wooden box frame is fine. Size maybe a factor if used indoors, then a 3-foot frame max.
3) Turns spacing of 1/8 to 1/4 inch is fine, actually down to a one-wire dia. gap.
4) An indoor loop may pickup home electronic noise, then worse than without one! That's the reason some mount the loop remotely, for min. noise pickup.
5) (Important) A loop is not used like say a vhf beam to max. a signal. No, it's used for better pickup (a tuned circuit with
  high Q) to minimize a possible offending station not in the directional plane as the station desired. Loops are broad that way.

A lot of this will become apparent by building a "starter" loop to get a feel of it. You didn't say if you've done that.

Oh, how to feed the signal from the loop to the feed line then to the radio. A lot can be said here, but a link coupled magnetically to the tuned loop works well. One turn inside or outside the loop frame. Try one-inch separation and join it to some twisted wire or coax on to the receiver, assuming a tabletop setup here.

That should get one started. I've been there, done that ... it works.

Peter