Cushcraft R-8 - eight band vertical HF-antenna
[20/Nov/2006]
With my present QTH a beam antenna is no option, but I wanted
a multiband antenna which covered as many bands as possible.
After some investigations I decided to put my money in the
Cushcraft R-8. I have now used the antenna since august 2002
(four years). I have in earlier years, in other QTHs, used
dipoles, random wires and a 3 element beam.
The R-8 consists of one main radiator with two traps (covering 7,
10, 14 and 18 MHz) with four parallel radiators (covering 21,
24, 28 and 50 MHz respectively). Additional impedance matching is
done with two capacitive crosses in the top section and a
matching network box at the feed point. The counterpoise consists
of 7 rods in the air at the feed point. An important argument for
choosing the R-8 was the counterpoise solution - the antenna don't
need an extensive radial system buried in the garden or spread
out on the roof. Therefore you can mount it on a mast, roof
etc.
I spent some evenings (totally 4-5 hours) assembling the antenna.
The manual was flawless, a lot of illustrations and no
ambiguities. The hardware is solid and overall well designed
mechanically. I was a little bit worried about the construction -
it seemed to me that the construction was too top heavy (the two
traps in the top section), but the antenna easily survived the
winds we have had so far.
I mounted the antenna on a wooden roof on a 5 cm diameter steel
tube, about 17 meters over the ground (1,5 meter over the roof)
with no guys. I definitely needed help from a friend in this
step! I was very accurate when I assembled the thing and that
paied off. I had a good match - well within the specifications -
on all bands and I did not have to take it down for adjustments.
It can be used on all bands without tuner, except for the 40 m.
Here it gives you close to 1:1 in SWR at resonance, but it's
quite narrow here. (You have to choose between the CW and phone
segments when you assemble it).
My experiences with the R-8 on the air are very good, actually
better than I hoped. I have worked a good piece of DX with it on
all bands except 6 meters (which I don't work) and the conclusion
is: This antenna is much better DX'er than a dipole or similar
wire antennas. I have compared it thoroughly with a windom (FD-4
at 10 m up with free horizon). On long distances it seems like
that the R-8s much lower radiation angle come into play. The
difference in signal strength is typically 3-4 S degrees on
distances over 4-5000 km. On continental traffic (within 3000 km)
the difference is not so distinct, and within Scandinavia the
Windom is often the best choice - again due to the radiation
angle. The R-8 is certainly no NVIS-antenna.
By now I have worked about 130 countries with it - amongst them
3Y0X on 30 meters. In the period 20.8.2002 - 20.8.2006 the band
statistics look like this on this antenna:
- 40 m 66 countries (550 QSOs)
- 30 m 71 countries (350 QSOs)
- 20 m 86 countries (350 QSOs)
- 17 m 44 countries (100 QSOs)
- 15 m 32 countries (50 QSOs)
- 12 m 25 countries (35 QSOs)
- 10 m 30 countries (75 QSOs)
This was in the lowest period of solar cycle 23 with - as you
see - modest activity.
An negative side worth mentioning is that the vertical often
picks up more man made noise than a horizontal antenna. That might
be an important aspect if you live in a noisy environment. My
antenna's location on the roof is relatively close (10-12 m) to
the my neighbors' numerous electronic spotlight transformers.
They produce rather strong noise on some bands. In such cases I
use the windom as a listening antenna.
With its low radiation angle and eight band antenna tuner-free
operation the R-8 vertical shows some distinct advantages
compared to a simple wire antenna such as dipoles, windoms and
random wires. Even if I sometime in the future will be able to
put up a yagi again I'm quite sure that I'll still have the R-8
up in the air. The combination of good DX performance, 360 degree
coverage and its good multiband design it will be a good
supplement to a beam.
Pros:
- Easy to assemble
- Easy to locate (no ground radials)
- Low profile appearance (neighbor friendly)
- Good DX performance compared to a dipole
- Mechanically very solid and professional construction
- Plug and play I: No adjustment iterations needed (in my case
at least)
- Plug and play II: Resonant on 8 bands - no tuning needed (but
you have to choose CW or SSB on 7 and 50 MHz)
Cons:
- Expensive
- Picks up more noise compared to a horizontal antenna
- To raise the antenna is no solo project - help is needed
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