Another way of getting on HF with a "compromise" antenna:
Use a random-length
dipole with a remote L-network, relay-switched
autotuner mounted at the feedpoint; then run your coax from the tuner to your radio.
A common-mode choke on the coax near the tuner may be needed to keep the RF out of the
shack. There are a number of very efficient L-network, relay-switched autotuners available
that can match a very wide range of antenna lengths all the way from 160 through 10
meters. Some also cover 6 meters.
If you're considering an amplifier, the high-power
autotuner models tend to have narrower matching ranges and tend to be considerably more
expensive than the 100-300W versions.
SGC, MFJ, and LDG each sell a variety
of these. The important part here is to choose one that has low loss when matching a
wide impedance range. Some models require control/DC power wires; others don't. Some
have remote-control heads with manual tuning buttons & power/VSWR meters, others
don't. Some will connect to a radio's CAT port, some don't. Most will tune with a just
a low-power carrier (say, 5-10 watts). Usually, the circuitry measures your transmit
frequency and automatically finds the most efficient match in a few seconds or so. The
tuning solution is then stored in memory for nearly instant recall when you key up near
the same frequency again. Some of these autotuners have thousands of memories. Many
of them can efficiently couple power into a 40' dipole, or even a 23' ground-mounted
vertical from 160-10 meters. For some of these, the only cable you need is the coax
between the unit & your rig - the DC power is fed through the coax, using a device
called a bias-T, and the tuning is done simply by briefly keying-up your radio at low
Attic-mounted, efficient antenna for
160-10 or 160-6 meters:
Build the longest dipole that will fit the attic,
and mount one of these L-network autotuners directly at the feedpoint. Operate 160-10
or 160-6 meters on one antenna - with little loss from the tuner or feedline.
For horizontal antennas, antenna efficiency = radiation resistance/(ohmic resistance
+ parasitic losses). The key to efficiency with a short dipole is to use very low resistance
wire for the radiators & use an efficient matching system. This is because a short
antenna tends to have low radiation resistance. For a short vertical, a low-loss ground
system is also very important, as the efficiency of a ground-mounted, Marconi-style
vertical = radiation resistance/(ohmic resistance + ground system resistance + parasitic
Since it's mounted indoors, the efficiency will likely be a bit worse
than when mounted outdoors in the clear - due to parasitic losses such as metal conduit
or wiring in the walls. A snow-covered roof can also reduce the performance of attic-mounted
antenna is really short for the band you're tuning, its radiation resistance will likely
be very low. In this case, a few ohms of wire resistance and/or 10-20 ohms of ground
system resistance can cause much of your signal to be wasted in heating up the wires
and/or heating the earthworms.
As others have said - the "UHF" connector is not an
issue on HF or 6 meters, and is likely not an issue for casual operation on 2 meters,
unless you're into weak-signal or EME.
Belden 9913 is a good choice for indoor use, however a number
of people have had moisture problems with it when used outdoors. An alternative with
similar performance is Belden 9913F7. The difference is that the 9913F7 uses a low-loss
foam dielectric instead of air, like 9913 uses. This solves the moisture problem with
little increase in the loss. At 150 MHz, a given length of 9913F7 has only slightly
more loss than the same length of 9913 - not enough difference to notice at all at the
Another efficient "compromise"
antenna (outdoor mounting only):
I'm very horizontal space-limited, plus
- I'm renting the house. Fortunately - there are no antenna restrictions. Here's what
I did to put out a decent signal at useful launch angles and in the most directions
- on 160-10 meters - with only one antenna:
My lot is not large enough for long,
high, horizontal antennas. I wanted to operate on 160-10 meters, and wanted to have
a low angle of radiation on 160-20, so I could work some DX. I wanted as close to an
omni-directional pattern as I could get on 160-20 meters, as well. I also wanted to
rag-chew on 75 meters with the locals.
My solution was to build a 100' inverted-L
- with the horizontal & vertical legs each 50' long; bury (33) 30-foot radials in
the yard; and mount an SGC-230 L-network autotuner at the feedpoint. I hung the antenna
from two trees - the vertical radiator just hangs down & is tied to the ground with
a small bungee cord. From a distance, the antenna looks like a flat-top "T", except
that one leg of the top of the "T" is rope. I operate this antenna from 160-10 meters.
I put it up last November,
and have logged a fair number of DX contacts on 40 & 20 meters using SSB @ 100W
- and I'm not a contester - just a casual operator. Plus, it plays very well on the
my radial field is quite small for 160 meters, it works surprisingly well down there.
I can work a fair number of stations out to ~1000 miles or so on summer evenings, using
SSB with 100W. In the winter, I can work most of the NA continent, but have yet to work
any overseas stations.
On 75, 40, and 20 meters, most stateside & DX contacts are very surprised
to learn that I'm running only 100W. Same thing on 75 meter local rag-chews - most think
I'm running an amp. I enjoy some DX on 75-20 meters (mostly on 40 & up), and can
sometimes bust pile-ups on 20 meters with my little 100W station. However, I have yet
to work any DX on 75 SSB with it during the summer months. To date, my longest DX contacts
on 40 & 20 meter SSB have been in the 5,000-6,000 mile range.
It has a number of high-angle
lobes & deep nulls, however it also has some useful low-angle lobes with a lot of
gain. In the favored directions, it performs very well, but the nulls are deep - I may
work someone @ 20-over 9, but someone 20 degrees off the lobe may be in the noise.
Considering the poor band conditions over the past year, not too shabby for
a "compromise" antenna, I think.
There are ways of getting on the air with a decent signal - even with short and/or "non-resonant"
antennas. It's a matter of minimizing your losses.
On the other hand - I remember
something an old ham once told me: Any antenna
is better than no antenna!
Good luck & hope to work you on the bands!