Hi Ed,
I find your SWR readings a bit contradictory to my antenna modeling
in EZNEC.
Modeling 4 radials 17.28' each and a radiator of the same length
with the radials 7' off the ground and the ends and the feed point and feed
end of the radials at 10 feet I get a SWR of about 1.6 to 1. If I change
the radiator to a 40' length and feed it the exact same way and heights I
get a feed impedance of 325 ohms and a reactance of -1147 Ohms for 14.06
MHz. which isn't what I would call acceptable.
For 7.04 MHz I get it near perfect with SWR of 1.19 to 1, at 59.5
Ohms and -1.169 Ohms reactance. Very Nice.
30 meters comes out at 10.12 MHz with 283 Ohms and +828.7 Ohms
reactance. SWR of 54.2 to 1. Not very nice.
So, unless you are running a tuner and that was the best your tuner
would adapt the antenna to your rig, then I can see where you got your
numbers. Either way, the antenna on any band except 40 meters is not going
to radiate very well UNLESS you install the tuner AT THE FEED POINT of the
antenna so the COAX is not contributing to the losses in the system. Even
then I would recommend looking at the radiation pattern and angle of attack
for that antenna and see it is what you wanted.
A 20 meter ground plane antenna as I first described has a very nice
single lobe pattern with an angle of attack of 20 degrees and a very
acceptable SWR. On 40 meters with the 40' radiator it runs 22 Degrees angle
of attack so again, a nice antenna with a very nice SWR. Make the entire
antenna as a 40 meter ground plane (double the 20 meter wire lengths with
same height above ground) and you get 1.12 SWR will NIL for reactance and
the same attack angle of 22 degrees. Very close to your 40 foot radiator
model.
So, how did you get your SWR readings? Tuner or No Tuner? And
located where?
Best 73 72
Michael Baker K7DD
[EMAIL PROTECTED]
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Edward R. Breneiser
Sent: Friday, October 06, 2006 7:55 AM
To: elecraft@mailman.qth.net; [EMAIL PROTECTED]; [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Subject: [QRP-L] WA3WSJ: Bead-Wire Antenna
Hello all,
I received lots of emails concerning my "Bead-Wire Antenna."
I've decided to post on the reflectors rather than send out to each
Individual op.
Here's what I did to make my antenna. I went out to my local craft store
called " The Rag Shop" and bought a 40' spool of flexible bead wire.
This stuff is very strong, has a clear tough plastic coating over it,
but won't take solder. My wire has seven strands to it. It comes on a
plastic spool that's about 2.75" in diameter and 5/8" thick. It even has
a clear plastic cover that snaps over half the spool to keep the wire
etc on the spool. The wire measures .012" in diameter so it's very small
and light. In fact my 40' of wire and 40' fishing line with spool
weighs-in at less than 1oz!
I tie one end of the bead wire to 40' of 30lb test fishing line. On the
on the fishing line I tie a loop. I tie about an 1" loop on the end of
the fishing line so I can attach a 1oz lead sinker. The sinker is one
that is egg shaped and has a wire loop at the top. In the field I simlpy
slip the fishing line loop through the wire loop and double back over
the sinker. This makes for a solid tie that can be taken off easily
anytime. This sinker makes it easy to throw up the bead wire into a tree
too.
At present I use three ground radials each 16' in length made from #26
black stealh wire. I plan to make my ground radials out of the bead-wire
too to save on space and weight.
I tried this setup yesterday in my back yard with my KX1. On 30m I had
4.0W out with a 1.0:1 swr. On 20m I have 3.8w out with a swr of 1.2:1
and on 40m I have 2.8w out with a swr of 1.1:1.
My entire trail radio package weighs-in at 1.6lb. Here's what I use on
the AT:
Radio: KX1 with 30m option
Battery: Powerizer 11.1V 1800mah 3-cell Lithium Polymer ~4.5oz
Antenna: Bead-Wire Ant. Attached with 2-post to bnc adapter
Paddle: AT Paddle Mini (plugs directly into KX1, 3.5mm stero plug)
The entire package stores in a small camera case!
p.s. You can buy silver coated bead wire to solder to, but it's
expensive!
72,
Ed,WA3WSJ
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