160m J-pole?
 

I was thinking (rare - lol), what if I used
rat shack 300 ohm twinlead and made a
J-pole for 160 meters? The antenna would
be sling shotted over several nearby trees
or baloon lifted.

Seems too simple to work, eh? Or am I
missing something here?

Ken KG0WX

On Sat, 27 Dec 2003 10:59:11 -0700, "Ken Bessler"
wrote:

I was thinking (rare - lol), what if I used
rat shack 300 ohm twinlead and made a
J-pole for 160 meters? The antenna would
be sling shotted over several nearby trees
or baloon lifted.

Seems too simple to work, eh? Or am I
missing something here?

Ken KG0WX


Hi Ken,

Try for the balloon method, but be careful to have a long non
conductive tether to the balloon. The high potential at the end of
the antenna can blast it apart - we won't go into the fate of the
Hindenburg (yes, I know the difference between Hydrogen and Helium,
wanna experiment?).

As for laying it across trees, this hi-Z design will be looking at two
near shorts: the tree limbs it lays across, and the proximity of earth
that would be much closer than if held aloft by the balloon.

73's
Richard Clark, KB7QHC

Ken Bessler wrote:
I was thinking (rare - lol), what if I used
rat shack 300 ohm twinlead and made a
J-pole for 160 meters? The antenna would
be sling shotted over several nearby trees
or baloon lifted.

Seems too simple to work, eh? Or am I
missing something here?

Ken KG0WX

Well, the slingshot should probably be made from a truck inner tube and the
balloon would be one big balloon.

A six foot helium balloon only has a few pounds of lift.

A few minutes with a calculator and the weight per foot of twinlead
would be enlightening.

--
Jim Pennino

Remove -spam-sux to reply.

Ken,
Too simple to work? Not really, just very impractical to
erect on an 160 meter 'scale'. Pictures after you get one
up would be nice...
'Doc

'Doc wrote:

Ken,
Too simple to work? Not really, just very impractical to
erect on an 160 meter 'scale'. Pictures after you get one
up would be nice...
'Doc


It'd work fine if he was on the Space Station. But in a 1G gravity
field, there
are definite issues to deal with....

Robert,
Sort of impractical, huh?...
'Doc

Robert Casey wrote:

'Doc wrote:

Ken,
Too simple to work? Not really, just very impractical to
erect on an 160 meter 'scale'. Pictures after you get one
up would be nice...
'Doc


It'd work fine if he was on the Space Station. But in a 1G gravity
field, there
are definite issues to deal with....


Beginning with a 120 meter self supporting or non-parasitically guyed
vertical.

Ken Bessler, KG0WX wrote:
I was thinking (rare - lol), what if I used
rat shack 300 ohm twinlead and made a
J-pole for 160 meters?

Hi, Ken,

Some suggestions:

1. go to http://www.cq-magazine.com

and download VE3ERP's (George Murphy) HAMCALC
freeware package of 250+ ham radio programs,
one of which is Murph's version of my version
of N3GO's (Gary O'Neill) J-pole design program
from his Communications Quarterly article.

2. Check out AA5TB's (Steve Yates) web site
that discusses J-poles and horizontal Zepp antennas.

http://www.qsl.net/aa5tb/

including a link to N3GO's article.

3. You can use just single wire for the half-wave radiator
and the twinlead for the not-quite-quarter-wave matching section.
For 3850kHz their lengths would be about 121.3 feet
and 58 feet tapped at 21.6 feet from the shorted end
for a 50 ohm feed tap. This assumes about a 1000 ohm
feed impedance for a low, horizontal half-wave radiator.
A vertical radiator feed impedance would be more
like 2000 to 4000 ohms. The matching section can be
at right angles to the radiator if you don't have
180 feet to stretch it out.

This is the theory. Go measure and cut copper
and plastic and let us know how you make out
in real life.

Have fun.

Cheers, 73,

Ron McConnell



N 40º 46' 57.9" W 74º 41' 21.9"
FN20ps77GU46 [FN20ps77GV75]

http://home.earthlink.net/~rcmcc

A J-pole is just an end-fed half-wave and a matching section (which
also radiates some). On 160, the matching section won't be
particularly efficient if made from twinlead. Look for the discussion
that went on here earlier this year, I believe, about the Q of a
transmission line resonator. It's pretty terrible for small line at
lower HF frequencies, but is quite good for the same size line up at
UHF. So, you're probably much better off to use an "L" network made
from a series inductor and shunt capacitor, and to provide some sort
of counterpoise or ground system to operate against. Then you only
have to hoist 1/2 a wave of single-conductor wire with your balloon --
or something up in the trees but I hope fairly well insulated from
them.

Cheers,
Tom

"Ken Bessler" wrote in message ...
I was thinking (rare - lol), what if I used
rat shack 300 ohm twinlead and made a
J-pole for 160 meters? The antenna would
be sling shotted over several nearby trees
or baloon lifted.

Seems too simple to work, eh? Or am I
missing something here?

Ken KG0WX

as a vertical, I think this antenna exceeds the max hieght of an amateur
antenna, which is 220 feet.
a half wave with a quarter wave at 160 is 80 meters plus 40 meters approx,
which is approx 360 feet vertical.