HF Antenna
Dale Gillilan
sailing mast? I want to work ham bands and Marine SSB.
Our boat already has RG-8 coax installed to the top of the mast, so I am
looking at that route instead of modifying the backstay. I am open to
suggestions, though.
email responses are welcome.
Thanks,
Dale
Larry KN4IM
but simply imbedded into the fiberglass. We added an extra nut to one
of the bolts and used a big eyelet terminal. This became the "hot
side" connection for a longwire tuner (not the little coax tuner
inside transistor rigs, they can't handle it.). The SGC tuner, around
$500 for the 200w model, comes to mind. It's fast and fully automatic
remembering the last 2000+ settings in milliseconds....
Ground the tuner to the bottom of the mast and it forms a delta loop
with a huge capacitor hat from the other stays. We were S8 in Perth,
Australia with a 100w Yaesu FT-900 docked at the marina on 20
meters....(c;
This antenna is a DC ground, grounded by the mast to the engine and
sea, I hope. No static buildup across the tuner or rig antenna
connections. Works great...even on 80 and 160M!
73, Larry KN4IM/MM
pkhen...@my-dejanews.com
Dale Gillilan <positivechan...@gte.net>
wrote:
> Any suggestions on what to use for a broadband
HF antenna on top of a
> sailing mast? I want to work ham bands and
Marine SSB.
>
> Our boat already has RG-8 coax installed to the
top of the mast, so I am
> looking at that route instead of modifying the
backstay. I am open to
> suggestions, though.
>
> email responses are welcome.
>
> Thanks,
> Dale
>
>
Wauquiez Hood 38 that satisfies your criteria for
a multiband marine/ham HF antenna. I refer to the
antenna as a multiband simulated inverted-V
dipole. I installed a 4:1 current balun (cost $42)
at masthead. The input of balun is connected to
radio/tuner via 75 feet of low loss RG-8U coax run
inside mast. The first output of balun is
connected to insulated backstay (or insulated
wire) and the other output is connected to
uninsulated forestay. The forestay (and rest of
rig) act as counterpoise to the backstay. In my
situation the bottom of mast is grounded to a
dynaplate for lightening protection, but otherwise
the rig is ungrounded. This antenna tends to be
more omni-directional than an insulated backstay
since both forestay and backstay radiate. This
antenna tends not to interfere as much with
onboard electronics since there is no ground plane
surrounding all your sensitive electronics. The
performance is superior. Several experienced
antenna experts said that this antenna has the
advantage that the high current feed is high in
the air. While I don't understand the full
significance of this it must be a good thing! The
antenna happens to resonate on 80 meters with an
SWR of 1.05:1. That was a fortuitous thing that
was not planned. I have successfully tuned the
antenna over all bands with both the MFJ-969
manual tuner and the ICOM AT130 automatic tuner.
My second antenna is more specialized since it is
designed to resonate on 20 meters. It is also
balanced and is, in effect, a short (loaded)
dipole. It consists of two 20 meter loaded whips
mounted horizontally in opposing directions from
the masthead (the overall width is just over 14
ft). I ran 75 feet of flexible RG-8X directly from
radio to antenna. No tuner or balun was required
since it has a 50 ohm impedance. The SWR is in the
range of 1.3 to 1.6:1. A dipole mount can be
purchased for $13.95 and each whip cost $19.95.
Therefore, the total cost was just under $54 not
counting the coaxial cable! Since I do 99% of my
ham email on 20 meters having a specialized
antenna that required no tuning seemed worthwhile.
Also, I had no idea about relative performance in
advance. BTW, on some days the short dipole works
better than the inverted-V and on other days the
inverted-V works better.
As far as my design criteria goes, I wanted a
balanced antenna since my experience with ground
planes (ie, unbalanced antenna systems) was quite
negative (eg, difficult to implement well, tend to
create onboard interference, limited performance,
etc). It all started when I built a half wave
dipole and strung it between masthead and stern
quarter. The performance was unbelievable and no
ground plane or tuner was needed. At that point, I
knew the bottom fed insulated backstay was
history! The only problem with that dipole was the
routing of feedline. The feedline interfered with
the swing of the boom and was not robust enough in
rough weather (it broke and had to be repaired on
more than one ocassion). Eventually, I was forced
to consider designing an antenna that had most of
the benefits of the dipole without the logistical
disadvantages. The two antennas described above
came out of that effort. Neither antenna is
affected by swing of boom or weather. In fact,
since both antennas are fed at masthead they are
far from the salt spray that causes havoc with RF
connections. Good luck and let me know if I can be
of help.
Pete/kf4tvu
email: pkhe...@gate.net
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pkhen...@my-dejanews.com
satisfies your criteria for a multiband marine/ham HF antenna. I refer
to the antenna as a multiband simulated inverted-V dipole. I installed a
interference, risk of electrolysis, limited performance, etc). It all
Pete Rimmel
in South Florida, and have helped many others get their radios working,
and trouble shoot those that were not. You have to face it, unless you
want to put a 16-32 foot vertical off the transom, you ONLY GOOD
solution is to insullate the backstay or some other stay not near the
mast (that excludes the shrouds, since they are really too close to the
mast, usually grounded, to be a good radiator.)
Bite the bullet and insullate yaour backstay. Make sure that the top
insullator is no closer than 4 feet from the mast, to keep the RF away
from the Mainsail headboard which may be metal. The other insullator
should be higher than a person can reach form deck, and then run high
voltage insullated wire from ther through the deck to the tuner.
You get what you pay for... You can't expect the rig to radiate without
making it electrically capable to do so.
I do know of some people, on larger boats, who can rig a separate wire
similar to a backstay in a location which is away from all the other
metal 'wires' going up the mast. Also if you have a split rig, you can
run coax up the mizzen, and rune an insullated wire ABOVE the triatic to
the main mast.
Hope this helps. Don't be afraid to install insullators-- they usually
have a breaking strength higher than the wire you install them in.
73,
Pete Rimmel N8PR
Marine Surveyor (among other marine occupations)