If you have a postage-stamp
garden, you'll never get a signal out on HF. Those of us who are blessed with a
garden that's the size of a postage stamp are doomed to be stuck on VHF forever.
I see, hear and read about this
this quite often, at our radio club, in magazines and from other licensed radio
amateurs, so it *must* be true, right? Err no,
it's plain wrong. It's a load of old cobblers really, and I hope to prove to
some small degree, how wrong this assumption really is.
When I set up my current HF
station, I went out of my way to make things less than easy for myself. I
used a 25 year old radio, bought for £100 and I made my own aerial... a
deliberately poor aerial, in a poor location, just to see what was *actually*
possible in a limited situation. In the event, it wasn't much of a
limitation really. Should you have a limited space for aerials, you *do*
still have options that will get a signal out reasonably well. MY own back
garden looks rather like a small wedge of that well-known soft squishy cheese
that comes wrapped up in tinfoil.
If you have the space for a
dipole, or an inverted Vee, even with drooped ends, on the band of your choice,
I'd suggest you read no more, put one up, and look elsewhere in this website!
For others with less space than
that, you need to compromise. Your options really fall into two main
categories as I see it, loops and verticals. I won't consider the other
various 'miracle' options. Miracles as far as I'm concerned relate to trickery
and as we know, trickery like miracle aerials is bogus!
Small transmitting loops can be
pretty effective and don't need to be mounted high. They will work fine a few
metres above ground, and properly designed, can be very efficient on 20M and
above. The main thing to remember with loops is that high voltages are
involved and that due care must be made to protect members of the public from
being 'zapped'.
Verticals have a bit of a bad
press. The one I hear most often is that 'verticals radiate equally badly in all
directions'. Well, that's not quite true of course. They don't
radiate UP or DOWN very well :-) Done properly, they *can* offer useful
low-angle radiation.
The other thing I hear said about
verticals is 'if you have the space for a vertical, put up a dipole instead'.
This is a reference to the need for 1/4 lambda radials disposed around the base
of the vertical that form the 'other half' of the radiation structure. In
large part, this one *is* true, because a typical 1/4 wave vertical does
need radials or a counterpoise system. What's not being said often, is that the
radials can be a compromise, so a vertical *can* be made to work in a
compromised location.
Because of my lack of space, I
have done everything in my power to make the ground system as good as I can.
Don't hammer in a 1M spike and expect that to work as a ground for a vertical.
In normal soil, it'll be rubbish! You need to 'work with what you can'.
In my case, I used an edging spade of the sort used to trim the edges of grass
borders... to make slots in the grass radiating outwards from my vertical
aerial, into which I pushed ...literally every piece of wire I could find in the
house.. and at work. Lots of wire! To poke the wire into the slots, make
yourself a 'pusher-stick'... a simple stick with a notched end. Bare
wire , insulated wire ... anything will do.
You can also 'dog-leg' your radials to fit more wire into less space. If you can
get your hands on an SDS hammer-action drill/chisel, use a half-inch adapter and
a half-inch or similar
sized socket wrench as a hammering tool for it, to bury a few copper, steel or any other sort of solid
metallic rods you can find, in the earth, to 'beef up' your ground system
(taking due care not to damage any of the water, gas or electrical services
running to your home). You can never really have too much wire in the
ground. More is always better, and many short radials seem to work better
than a few long ones. Don't fuss too much about the length... just get that wire
into the ground.
Unless you plan to dig there, you
can bury the wire close to the surface. The slots for the wires need only be an
inch deep and the grass will soon grow into the gaps. Once 'planted' just
stomp the grass back down with your boots. In flower beds, dig quite a
lot deeper!
When my neighbours went on
holiday to Tenerife for three weeks, this was a great opportunity to bury a load
of wire on their side also. You have to be creative when it comes to providing a
good RF ground.
By comparison with my ground
system, the radiating element of my aerial itself is a big disappointment. It's
made from a piece of thick-walled scaffold pole about 5 feet long, placed in a 2
foot deep hole in the ground and hammered in as far as I could manage, so about
18 inches protrudes above ground level. All of the wires from the ground
system connect directly to this pole. I then filled the hole with a mixture of
rocks and dry 'Postcrete' mixture and poured water onto it, after making sure
the post was as straight as I could measure. Postcrete is a very fast-setting
concrete mixture. Once set, I filled the remainder of the hole with earth.
It's situated in a flower-bed, so is very unobtrusive. While I was at it, I
bonded the post to our cast-iron waste-water plumbing for good measure. A heavy
insulated wire runs from the pole under the grass and is connected to a
stainless-steel-bolt that's screwed into the massive cast-iron drain at the rear
of our home.
The radiating part of the aerial
is very simple indeed. It consists of nothing more than the remains of an old
carp fishing-pole with about 5.5 metres of stranded electrical cable threaded inside it.
I sticky-taped all the sections so that the pole could not collapse down on
itself.
At the feedpoint is a home made
9:1 UN-UN. I used a T200-2 core trifilar wound with ordinary plastic covered
solid hookup wire. The UN-UN is fitted into a sealed plastic box into
which I poured melted candle-wax as a poor man's potting compound. The
feedline back to the house is just some RG58. If you have a long cable run
(unlikely in a postage stamp garden), you may want to use Mini-8 instead.
Now an aerial like that is never
going to let you compete with the big dogs in a pileup, but it will get you out
and especially on the datamodes where it works quite well. I took a page out of
my eqsl-log and pasted it in here to let you see that you can indeed operate
from a restricted location without much difficulty. My PSK contact listed
below with IZ0SAT was very interesting for me because it was my first QRP
fishing-pole to fishing-pole contact. I also had a contact into Southern
France on 800mw on one occasion (not listed below... no EQSL). The contacts
below are only some of the ones I've made with this simple aerial system.
The power levels used for my BPSK contacts ranged from 800mw to 40W(maximum),
with an average of around 20 watts. Although it's nothing special, one of
my contacts with this simple aerial was into the US at over 4600 miles on fairly
low power. Trust me, operating skill and propagation conditions count for
far more than big aerials and brute force.
If anyone on my list below
reads this, I'd like to offer you a big thank-you for being an unwitting part of
my experiment.
I do eventually plan to replace this
deliberately poor aerial with a better one sometime, but to be honest with you,
I'm making plenty of contacts with it and in no way is it a disappointment. On
the contrary, I'm often surprised by it and I consider it to be a good success.
