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Butternut HF9V Vertical as a Ham Radio ALE Antenna
Benefits to the ham radio ALE operator: No tuner needed. Provides low SWR on ALL the HF ham bands, good RF efficiency, durable construction, light weight, with convenient installation.
Click on any photo to zoom.
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The Butternut HF9V Vertical
as a Ham Radio ALE Antenna
an article by Bonnie Crystal KQ6XA
After using this antenna for a short
time, my initial impression is that I believe it has excellent
potential for ham radio ALE station operators as an efficient
vertical to cover the HF ham- bands- only. Here's the background story of
my experiences selecting it, assembling it, putting it up, tuning the
antenna, and how it performs on the air for 80m-10m ALE operation.
I Operate an ALE HFN Pilot Station at
one of my QTHs in tropical East Asia. Typically, it is common for us to
see severe
weather and fierce gusts every year in this Pacific coastal zone. HF
antennas here must be durable, or they simply will not survive.
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Prior to this, I've been using a stout dipole broadband coaxial antenna system
of my own design... it has a low SWR from 3.5MHz to 60MHz... but trades off a
little negative gain to achieve a DC to light match to 50 ohms. The
receive performance on the broadband dipole is good, but the transmit
effectiveness for low angle DX is somewhat less than optimum. Normally,
this sort of workhorse antenna is great for ALE; but watching the dipole dance
around like a crazed deadhead in the recent storms, made me a bit concerned
that one of the trees that supports the end of it could be blown over
in a typhoon while I'm away from the station on a business trip.
At first, I started to think about installing a back-up antenna --possibly a vertical-- that
could be switched over to, if the broadband dipole came down Then, I became attracted to the idea that the
station performance and coverage area could be increased at the same
time. To cover this remote area of the world with a better transmit
signal, more effective radiated power would be needed. The trick is to
combine this with DX take-off angle high-efficiency on all the higher
HF bands, a minimum of roof space, and survivability in the bad weather
without constant maintenance.
The choices all pointed to an HF ham-band ground-plane vertical on top
of the station building. Given the fact that the season has had some
particularly severe typhoons,
and my work schedule left little time for antenna work, I decided to
look for a commercial antenna rather than succumbing to my engineering gut instinct to redesign the wheel and build one from scratch. While shopping around on
the internet to see what commercial antennas exist, I began reading
reviews written by hams who had been using various brands of verticals.
But, I found very few antennas out there that met the one key
requirement for ALE... a resonant vertical with coverage of the
80-40-20-30-20-15-12-10 meter ham bands, without need for a tuner.
Then, after reading one review, I recalled my earlier experience years
ago, in 1980, when I put up what was then a strange new multi-band
vertical at a friend's QTH. It was called the Butternut Vertical.
I was really impressed back then with the elegant design and practical
aspect of being able to change to any band and just start talking. That
was way before ALE was widely used on HF, but the need for this basic
principle of instantaneous all-band operation is the same. I found the
recent satisfied reviews of the Butternut model HF9V, and realized
that this line of antennas has been in production for almost 30 years,
with the basic construction relatively unchanged. Tried and proven, I
thought to myself.
After a friend picked up a Butternut HF9V antenna at an HRO store
and sent it to me, I ordered the companion tripod roof mount with
multiband radial kit. I received the antenna in the first shipment, but I'm
still waiting for the tripod kit to arrive.
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But in the mean time, I assembled the antenna in my workshop and
hallway. It took about 4 hours to put together, following the
instructions carefully, and matching the parts up to the description
and drawings in the manual.
The aluminum coil resonator contraptions are added one by one to the
aluminum tubing sections, and bolted in place. A few other rods and
straps are carefully clamped. The parts are well-machined, but
special attention needs to be paid to the burrs and particularly
handling of the fibreglass insulators, because these may cause tiny
glass slivers to be embedded in one's fingers and hands...
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Part of the 4 hours of assembly time, was spent with tweezers removing
the micro-fibres while looking closely under an illuminated magnifying
glass!
As I found out, after assembling all the resonators and putting the
last tubing tip in place... the antenna is too large to get out the
door, around the hallway corners, and up the
stairwell to the roof! So, I partially disassembled it temporarily into
3
sections at convenient points and carried it up one by one to the
terrace, where the last 2 bolts were inserted to hold the middle
sections together, and the 15 meter stub resonator wire was re-strung
like a violin bow.
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I easily tilted up the lightweight antenna by myself without any problem. Then I attached it temporarily
to a
metal roof terrace railing, along the edge of the roof, to test it out.
A large piece of plastic insulator sheet was first cut up and attached to the railing to
prevent the base section from shorting out. Plastic cable ties were used liberally to lash everything in place for the test.
It is indeed unusual among commercial trapped verticals for the design to use most of
the full length of the antenna vertiacl radiating element for all the different
bands, but that is just what the Butternut HF9V does. It does it with
an ingenious arrangement of aluminum coil resonators, rods, tubular
sections, fibreglass insulators, a few heavy duty doorknob capacitors,
and some stainless steel nuts and bolts.
Of course, this type of
vertical antenna needs a good ground plane to perform well. The
vertical part is only "half of a dipole". I cut a quarterwave
radial wire for each of the following bands: 80, 40, 30, 20, 15 metres.
Then I attached all of them to the ground lug of the feedpoint, and
suspended them above the roof terrace at a height of about 1 metre, all
pointing in the same general direction, separated by a few meters
fanned apart at a point about 3 meters out from the base of the
antenna, and held in place by black dacron antenna cord. The 80 metre
groundplane radial I made is shortened to about 10 metres long and I
put a loading coil in it about 7 metres out toward the end. I don't
have space on the roof for a full-size 20 metre length of wire. I
already had the coil from another project, and this seemed like a good
use for it. Alternatively, I could have zig-zagged the wire or snaked
it around the roof.
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There is a shunt coil at the feedpoint that matches the very low
impedance of the antenna on the 80 metre band to 50 ohms, and also
provides a path for DC grounding of the vertical radiator elements and
static bleed off.
Perhaps this coil can be adjusted if needed to improve the match on 40
metres as well, but that is not indicated in the instructions, so I
left it alone.
I plan to add more radials to it later. But, the next part is,
getting it tuned. I wanted to completely avoid having to use a tuner,
so careful tuning of the resonators was found to be essential to
achieving a low SWR at the right place in the bands.
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At
this point I connected the supplied 75 ohm section of cable
feedpoint matching section, and a 10m long section of 50 ohm RG-58/U
cable to the radio rack downstairs. To measure the SWR curve, I used an
AIM 4170 antenna analyzer. The results of my tuning in progress, are
shown below, just before lowering the antenna to adjust the 15m and 10m
resonators, which are the uppermost sections of the antenna and could
be reached while the antenna was in place, with a step ladder. Despite
the curve not being centred in these two bands, the SWR was low enough
(below 1.7:1)
on the ALE primary data frequencies to use it, so I went ahead and
started
on-the-air testing with it as is. I will tune it up better after
I get the tripod roof mount installed, and complete the installation
with 2 radials for each band... except for 80metres, which I only want
to use one radial, to get better high angle takeoff, and I don't have
the space for a second radial. I feel confident that the SWR on 40
meters will improve somewhat with the additional radials, and I will be
adjusting the other bands to tweak them to their best match at the
desired points in the bands.
The on the air performance is as good or better than I expected. I've
been able to regularly copy ALE signals from Europe and Australia
stations that never before were seen on the log. Some DX signals are
very loud on the vertical that I could barely hear on the dipole. Also,
the first report came in today of my signal being heard in Australia.
Hopefully, within
the next few weeks, I will post more information about the performance
as I'm able to compare it against other antennas at my QTH.
I hope this encourages other operators to try this antenna for ALE.
73--- Bonnie Crystal KQ6XA |
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Note:
July 2009. After tuning the antenna and radials better, the SWR curve
is very good on all ham bands. The 2:1 SWR bandwidth of the Butternut
HF9V is now 50kHz on 80m, 200kHz on 40m, and the entire band on all
other ham bands 30m-6m. See SWR curve above.
Note: December 2009 - After slight bending of the mounting pipe below
the feedpoint of the antenna, during a typhoon with 60mph (100kph)
winds, the antenna was taken down and insulated guy lines were added to
provide better support for higher winds.
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