The best antenna is not the longest thing you can put up, unless one of the
many minor lobes you create will point exactly where you want to go at a
radiation angle you need, and this is highly unlikely, but it does sometimes
happen.
The best thing to do is decide where you'd like to reach, for example, which
continent. Are you a DXer or do you do mostly local rag chews? What
frequency bands would you like to operate, and what size constraints do you
have to live with? Are there any natural supports you'd like to take
advantage of? Do you need multiband operation? Do you have an deed
restrictions on what you can put up?
Study the radiation patterns of dipoles, verticals and if you have the
space, long wires.
Do you have a tuner?
Remember, no antenna creates RF to get "gain", they only focus it. The
ideal RF antenna would radiate equally well in all directions. Since you
live on earth, the effect of height is an issue, as is the ground effect on
the pattern.
The best antenna to start with for a newbie is a windom cut for the lowest
band that will fit on your lot. With this kind of antenna you can run all
harmonic bands (ie 80M will cover 40M,20M,10M while 40M will cover 40M, 20M,
10M) quite well and not require a tuner. Several of the WARC bands will
work ok too but the SWR may be a little higher. I regularly use my 80M
windom on all bands here, most of them without a tuner, and the rigs tuner
is good enough on the one or two where the SWR is just over 2:1 which isn't
an issue, it just causes the radio to reduce power.
The second best antenna is a vertical, but most newbies screw up the
installation. You either need 4 elevated radials or you need lots of
radials on the ground. Lots means 16 or more. Again, the literature is
full of information on these topics, and there was even an article a few
months ago in QST I think where someone did a study on the best use of the
wire for a vertical ground plan - ie more or longer radials for a given
length of wire to optimize results.
The vertical is a good newbie antenna because it radiates equally well (some
say equally poorly) in all directions. Although some of that will go to
places where no one lives, if you have a good ground plane the low angle of
radiation will be to your advantage. One caution, if you live with a lot of
neighbors around verticals pick up noise more than horizontal antennas and
this can be a big issue. In that case stick with a windom.
If you have the money and the time and a computer, try purchasing an antenna
modeling software packet. I use NEC4WIN but there are many. With this, you
can model various wire configurations quickly and see EXACTLY what they will
do in terms of gain/loss/pattern etc. This will save you a lot of time and
money building things that don't work.
Finally, if your interest is local ragchewing, a low horizontal antenna may
be just fine.
I have an extensive antenna farm here, quads, yagis, dipoles, verticals,
etc. and over the past 35 years I've tried everything. The best overall
antenna, the one that I keep coming back to as a standard or default for
comparison is the windom. This off center fed device is fed at a point
where the SWR is tolerable on harmonically related bands using a matching
balun. My favorite was made by Fritzel, but I don't think they make them
anymore, but an internet search will turn up several suppliers and/or plans
for your own. The biggest issue in a windom is just the balun, and I
recommend CWS Bytemark products if you can get them.
Again though, remember that once the lengh of the wire is greater than 1/2
wavelengh the pattern starts to form lobes that can give you a great
signal - somewhere - and an equally poor signal in other places. This is
true for a windom too, on its harmonic bands. That is why 40 meter windoms
exist (besides the fact that they are shorter).
One of the best ways to solve your problem is by reading. Fortunately these
days you can read about antennas for hours on the internet at no cost, but
the best books I've found over the years are the ARRL Anthology series and
of course the ARRL antenna book.
73,
WT6G
PS Do not waste your time and reply to this email address. It won't work.
"ary" wrote in message
news
Vaughn,
It's quite easy: your best bet is the maximum length of wire you can keep
in your backyard AND as high up in the air as you can afford (trees,
towers, chimneys etc.)
To prevent RFI and TVI, make your antenna symmetrical. Feed it with an
open line, and connect the open line with your TX with an appropriate
coupler (the ARRL Handbook is a good source for information).
Please note you do not need to use a thick gauge of copper wire. Even a
thin gauge of stainless steel wire will do.
You will be pleased very much by the results !!
73 de PA0ARY
On Sat, 03 Jan 2004 18:38:59 +0000, Vaughn Combs wrote:
I have a few questions and I thought that this may be the group that
could
help. I have a nice sized backyard and would like to construct an
antenna
that would give me good performance on 80-10m bands.
The convenient dimensions would put a support (far end) at either 92
feet
from the back of the house (support exists that is about 15-20 feet up)
or
120 feet from the back of the house (mast anchored to the other side of
a
shed could easily be installed. Or a more inconvenient support could be
erected up to 300 feet out (no support buildings) at the absolute far
end of
the property. The width of the property as seen looking out the back
window
is about 65 feet (no supports existing on either side).
Special circumstances and constraints:
-- No tall trees on the property.
-- Attic shack (attic window is probably about 25 feet up). Need to keep
to
the attic.
-- Cable run from back of house to operating position within the attic
would
be approximately 25 feet
-- MUST eliminate RFI in the shack and house.
My current setup is an end-fed longwire that works well on all bands
except
40m (rig shuts down as I am dipping the SWR to almost 1:1 ;-). I threw
up
the wire as winter was upon me. I have been off the air for almost 10
years
and REALLY wanted to get on the air again.
While the longwire is performing quite well with the exception of 40m I
am
getting a ton of RF in the shack and it is blanking out TVs and creating
loud humming in speakers with 100W from the XMTR. I realize that this is
most likely due to the fact that I have inefficient RF ground and I have
cut
and run radial at 1/4 wave for each band and ran them under the eaves up
here in the attic. This has not solved the problem. I am friendly with
all
of my neighbors and have visited them and did testing on the bands with
them
on the phone. They are not experiencing any problems. My wife, while
understanding, would REALLY like the problem to go away ;-)
My main goal is to build an antenna that will solve the aforementioned
RFI
problem and that will provide good performance given my constraints.
Any ideas would be GREATLY appreciated.
Many Thanks and 73,
Vaughn
N2BHA
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