"John Pumford-Green GM4SLV" <[email protected]> schrieb:
> Hi LF gang,
>
> In my sked last night with Finbar (best conditions for some weeks) we
> discussed mini-beverage antennas laid directly on the ground. I've done
> a Google trawl and there's a bit evidence that they work well.
>
> I have a need to keep things low-profile due to all the adjacent fields
> being used for sheep, so running a long (100-200m) wire on the ground is
> attractive. I could even run it outside the fenceline along the verge
> beside the road - I'm in a very rural area.
>
> Does anyone have any experience of using BOGs on 500kHz?
>
> John
> Gm4SLV
>
>
Dear John,
in my available space in my garden I have not yet considered to try a
beverage antenna.
But I receive all VLF to MF signals (including the german DI-beacons
with an ERP of more than one watt) audible, using a simple untuned
vertical one turn wire loop of just 15 meters circumference, pointing to
the north, the lower wire being 2 meters above ground (so that it is no
obstacle when my wife is walking in the garden). I regard the reactive
impedance XL of this loop (which is dependent on frequency, of course)
as source resistance and match it to a coaxial cable via a torodial
ferrite transformer, thus making the loop independent or floating to
ground. As the loop area is quite small, noise ist also low, and a
preamplifier may be useful. But as this simple loop is broadband and
will also receive the powerful broadcast bands, an input selectivity may
become necessary before a preamplifier, especially with larger loops. So
far I do not have any experience, however, with loops lying on the
ground. I guess loops should have a certain plane or area above ground
(long beverages may be different), independent of their form. Mine is a
triangle.
In general I have experienced that loops close to the ground will be as
sensitive as high T or L antennas. Therefore I can recommend very much
to experiment with loops or even beverages. The match to beverages is
determined by its load resistance, of course.
My QTH is in southern Germany, eastern Bavaria, also rather rural, but
far from the sea.
HW?
73 Ha-Jo, DJ1ZB
|
