On 18/01/15 20:55, Bruno wrote:

I've had a planning application for a tower turned down which is a real
pain. My options are now very limited. I'm in a bungalow with a roof apex
height of 18 feet and I'm not allowed to put up anything much above this
roof line it transpires, so inverted vees that need to be mounted high up
at the feed point like G5RVs are not possible for me. My garden
boundaries limit the length of any wire antenna I might wish to put up to
about 120 feet overall. On the plus side, though, the QTH is several
hundred feet ASL close to the top of the hill and am not overshadowed by
any trees or buildings to speak of.

What's my best choice for an HF antenna under these circs?

You could have two...a horizontal, as suggested by others, and then
there's this....

Consider is using the slope of the hill to your advantage.

How close to it are you? Over what arc of the compass does the slope cover?

My thinking is that you should consider ground-mounting a vertical as
close to the slope as possible. The down-slope will pull down the
vertical radiation lobe to perhaps all but the horizontal, giving you
effective gain over a vertical operating over level ground together with
the prospect of long hop-length DX from the low angle. The difference in
gain can be useful to significant., and the reduced number of hops can
reduce path losses. Get a great-circle map and see what sector of the
world is covered by the arc of the slope; you'll get the best reports
from within this arc.

The vertical need not be high at all. For the lower bands you could try
the following set-up; you could make it in an hour or so. An auto-tuner
would make this a breeze, but you can put together the following from
your junk box.

Wind a coil having an inductance of 0.25 x lambda for the band of
interest. For 40m this would be 0.25 x 40 = 10 microH. I make my coils
from flex stripped from scrap mains cable. You'll also need a variable
capacitor of about 1pF per lambda, but this isn't critical. Connect this
across the coil. Wind on a 4-turn link at the 'bottom' end of the coil
connected to 50 ohm coax and connect to your rig. To the 'top' end of
the coil, connect your vertical. Mine is 18' of wire taped to a roach
pole, for the lower bands. To the bottom end connect four radials, each
as long as the vertical is high. Connect to a screwdriver or very short
rod earth via an RF choke or 1k resistor. Do not bury the radials or
connect a massive earth, this one is to bleed static, nothing more. The
radials will couple the RF to ground.

It's my experience that when the length of the vertical becomes a
significant fraction of the wavelength (say 1/10th), the system begins
not to work so well - the solution is to tap the aerial connection down
the coil, but this adds complexity. Keep the vertical section short and
enjoy the simplicity. This is a try-out of the possibilities of your
QTH, after all.

I find that this set-up is very non-critical, and with a 200pF variable
and the right inductance it will tune over two bands, say 160/80, or
80/60/40. Above these bands the link's turns will need to be reduced and
the system self-capacitance can be a nuisance, so perhaps an auto-tuner
would be better. Your output power will be limited by the capacitor's
capability voltage-wise. The only drawback is retuning for each band, as
the tuner is located at the base of the antenna. I use mine in the
portable mode, so operating near the base of the antenna isn't a problem.

Using a similar set-up on a short (200') slope facing East, I can work
all of Russia, the Mediterranean, and Asia from the UK with good reports
and running less than 10W, on 17 and above (for which I use an
auto-tuner). I don't work 20m, never liked the band much, and below
that, the slope isn't really long enough to pull the vertical lobe down.
Hopefully, yours will be.

--
Spike

"Hard cases, it has frequently been observed, are apt to introduce bad
law". Judge Rolfe

On Tue, 20 Jan 2015 16:09:25 +0000, Spike wrote:

How close to it are you? Over what arc of the compass does the slope
cover?

Good point. I'd forgot to specify that. I'm about fairly close to the
summit and the ground drops away mainly to the SSE with the coast about a
mile away. From here I can see couple of miles out to sea. Since I'm in
the centre of the British Isles, I'm in a great position for getting good
signals to and from South Africa - but not really anywhere else! :-(

On 20/01/15 21:40, Bruno wrote:
On Tue, 20 Jan 2015 16:09:25 +0000, Spike wrote:

How close to it are you? Over what arc of the compass does the slope
cover?

Good point. I'd forgot to specify that. I'm about fairly close to the
summit and the ground drops away mainly to the SSE with the coast about a
mile away. From here I can see couple of miles out to sea. Since I'm in
the centre of the British Isles, I'm in a great position for getting good
signals to and from South Africa - but not really anywhere else! :-(

What a beautiful part of the country! Many decades ago my parents
retired to live in a small village on the River Lune.

Pity about the take-off from your site :-( but the lower bands might be
well workable via a vertical. Use a horizontal for NVIS, and keep your
fingers crossed for some DX.

--
Spike

"Hard cases, it has frequently been observed, are apt to introduce bad
law". Judge Rolfe

On Tue, 20 Jan 2015 23:22:46 +0000, Spike wrote:

On 20/01/15 21:40, Bruno wrote:
On Tue, 20 Jan 2015 16:09:25 +0000, Spike wrote:

How close to it are you? Over what arc of the compass does the slope
cover?

Good point. I'd forgot to specify that. I'm about fairly close to the
summit and the ground drops away mainly to the SSE with the coast about
a mile away. From here I can see couple of miles out to sea. Since I'm
in the centre of the British Isles, I'm in a great position for getting
good signals to and from South Africa - but not really anywhere else!
:-(

What a beautiful part of the country! Many decades ago my parents
retired to live in a small village on the River Lune.

Pity about the take-off from your site :-( but the lower bands might be
well workable via a vertical. Use a horizontal for NVIS, and keep your
fingers crossed for some DX.

Ok, understood.

Well, I have more than enough info to be going on with for the time being
so many thanks to all who contributed to this thread and assisted in
clarifying my choices very effectively!

Bruno