Craig Buck wrote:
Read up on the topic of linear loading. You can bend that wire back on
itself and increase the total length of wire. There are discussions of
this in ON4UNs Low Band Dxing book. One commercial example is the
Cobra Ultralite at http://www.k1jek.com/.
I use a top center fed L. One side is horizontal and the other side is
vertical. Fed at the top center with ladder line. Cebik has several
articles on his site about center fed Ls. No ground plane, horizontal
and vertical polarization, fewer nulls in the pattern. Very nice
I think the center feds make a lot more sense for multiband operation.
You're absolutely right, Craig... in principle.
But Richard's situation reflects the reality for many British hams whose
house is at one end of a short and narrow rear lot. With neighbors very
close on all sides, we're lucky to have even one mast, so center-fed
antennas are often not very practical for us - they either sag in the
middle or wind up in a very sharp inverted-V configuration.
As a result, we're very much forced towards considering end-fed or
base-fed solutions.
However, I wouldn't go near an end-fed long wire or zepp configuration,
because of the very high risk of feeding the RF return currents into the
mains. Been there, done that, had the doorbell ring!
Living in that situation myself, my best solution has been a 30-33ft
vertical at the far end of the garden, fed against the best ground
system I can manage. This can be fed directly on 7MHz; with an ATU at
the base it is good for 10, 14 and 18MHz, and is usable on the higher
bands too.
Over the years, this system has acquired an auto-ATU at the base, and
has evolved into a guyed tilt-over mast with various quick-change
"accessories" that can be attached at the top. A lightweight 12ft
fishing pole makes a taller vertical, which has slowly crept up to 45ft;
or a selection of horizontal loading wires running back towards the
house at the 33ft level make inverted-L configurations for the lower
bands.
With the auto-ATU, any configuration can easily be loaded on any band.
It won't be optimum on more than one HF band, but it will get you on the
air on *every* band - and that's what counts for most.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek