On Apr 24, 2014 2:24 PM, "Stuart Rohre" <rohre@arlut.utexas.edu> wrote:
>
> Based on an article on loaded antennas in the latest QEX magazine from
ARRL, I would say a magnetic loop, if larger than 0.1 wavelength diameter,
might have either the same signal as a loaded dipole, (short dipoles as I
imagine you mean), or the magnetic loop will have BETTER signal to noise on
receive, which is very valuable in the indoor environment. Gain in the
receive, or low noise, may be better than more signal on transmit.
One could simply use it as a receiving antenna on the low bands.
>
> Both types of antennas would give better results if placed in an
unobstructed attic, (wood house), or placed at least, on the edge of a
roof. A larger than 0.1 wave loop could be hidden in a fenced back yard,
and even put on a pulley system that would raise it up to hang in a back
yard tree for after dark operations.
>
> Being indoors as now; you are in a cage or cobweb of electric wires,
possible metal plaster lath, and obstructions from large appliances on the
other side of a wall. You are subject to causing TVI to electronics inside
the home at least, or next door, or the next apartment.
Tell me about it - only the strongest signals can get through. Although the
situation might be better on 15M and 10M; I haven't tried.
>
> Of all the indoor operating means, the loop offers the best results,
especially on receive, if shielded, and made of low loss construction.
I'm going to look into it.
>
> Use large diameter loop material and low loss connections.
> One of the best loop designs for HF used copper tubing of 1 inch diameter
or larger, and was octagon shaped, because angled fittings were available.
The joints were silver soldered for lowest loss.
>
> The capacitors on the end can be trombone type made from sliding copper
pipes, with teflon tape as spacer and insulation. Or use surplus vacuum
variables which turn up at swap meets. Or even large metal air spaced
variables. while you might spend some money up front on material, (pipe)
and capacitors, those parts and the loop can be used for ANY future
locations, Field Days, or even mobile on a van.
>
> Locally, Bob, WB5AOH had one on his van that worked HF great on low bands
like 40 and 75. He would still have it but for a low hanging tree limb!
(With big mobile antennas back in bicycle days, I learned you have to
drive both the vehicle and the antenna!)
>
> -Stuart Rohre
> K5KVH
>
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