Topband: magnetic loop receiving antennas

Martin Jonink
Tue, 28 Nov 2000 15:48:37 +0100


I don't have any experience with ferrite loops. I live in a surburban
area as well and I'm using a 1/4 wave sloper for 80 and 160m. The sloper
is attached to a freestanding tower. As you can imagine..a beverage is
something that I can only dream of...
To complete the lowband antenna farm, I have build to versions of a
"magnetic" shielded loop.
The first one according to the ARRL Antenna Book design. This coaxial
shielded loop with sides of 1.5m woked very well together with a home
made preamp of about 12 dB. A lot of "surburban noise" is eiter non
existing or can be nulled out very effective. The only disadvantage was
the monoband design.
The second one is made out of alumium counduit (shield) with a total
lenght of 4m. Inside are two windings of small stranded wire.
With this particular design I can tune the loop with a 20pF capacitor on
80m, and on 160m with capacitance of about 350 pF.
Offcourse the output of these receiving loops is very low and you will
need some sort of pre-amplification.

It doesn't beat a beverage, but with the lack of space it's probably the
best for my location.

Martin PA4WM

Ted Roycraft schreef:
> In the "ARRL Antenna Compendium, Vol. 6", there is an article describing
> a tuned, ferrite rod, magnetic receiving loop antenna - "The Optima
> 160/80-Meter Receive Antenna" by Richard Marris, G2BZQ.  I'm tempted to
> build this thing to see what it does to my receive noise level on 160.
> The only reason I'm reluctant to go ahead is that the price of the
> required ferrite rods alone is over $120.  (It uses a total of 72 inches
> of 1/2 inch diameter Amidon type 61 ferrite rod).
> By the way, I'm using an inverted-L for both transmit and receive at the
> moment.
> I'm located on a suburban lot so anything like a Beverage antenna is out
> of the question but I'm still looking to improve my received SNR.
> Does anyone have any comments on this loop antenna or one like it?
> Thanks and 73,
> Ted, W2ZK
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