[Antennas] Hanging more wire.

2004年2月17日 19:39:15 -0600

For minimum results, the 1/2wl dipole or equiv in length of wire is what 
you want to shoot for on 80....going from 88 to 132ft will make some 
difference in matching...it will change the RF current distribution on 
the antenna to a better pattern than what you have now...
Since you have a short lot, I would make as much of the center of the 
dipole as high as you can get it then slope the remaining ends down to 
make up the difference. If you cannot get the full 132 ft, getting close 
should work ok....personally I would not go with a loop unless you want 
a cloud warmer...it will be quieter than the dipole but it will radiate 
pretty much straight up...the dipole will do a little better (though 
being say 45 ft to the ground is still too close to gnd for low angle 
take off...it should be at least 1/4 wave hi and thats 60ft!)
I would get rid of the 1:1 balun though....I would put 1:4 balun in its 
place to feed the 450 ohm line...and if you can put the balun at the 
back of the rig (I know that may not be possible since that would mean 
bringing the 450 ohm line inside), that would be best...but not always 
practical.
Chris
WB5ITT
(ALWAYS more wire or metal is better..in the right places)
Dan Evans wrote:
> To hang more wire, or less wire?
>> I have an 88' ladderline fed dipole, up in the trees about 45'. It works
> pretty well on 40 & 20, but doesn't tune well on 75m, being a bit short.
> I'm using the internal tuner in my '746, about 10' of rg213, 1:1 balun, and
> probably 60' of 450ohm ladder line.
>> I would like to get better results on 75m, and still use it on 40 & 20. [I
> have a vertical that does a decent job on 10 & 15]. What I would like to do
> is extend the dipole into a loop for 75m. But, living on a 100'x60' lot, I
> just don't quite have the real estate. What I can do is make a loop that is
> about 200' [at the same 45' average height], or I could lengthen the current
> 88' dipole to 130' and give it a "Z" shape.
>> I could also go with the 200' loop, and add a 'stub' of ladder line to load
> it for 75m....
>> What do you think? Hang more wire, or less wire?
>> Any suggestions greatly appreciated:-)
>> 73
> Dan

-- 
All outgoing/incoming mail scanned by Norton AntiVirus!
For ANYONE on the net, they should have an uptodate AV program!!