6 Meter long wire matching
Tom Azlin, N4ZPT
n4zpt at cox.net
Wed Jan 30 09:27:42 CST 2008
Well, I have been corrected.
According to Mike Toia, K3MT, when you add multiple half waves the
resonate impedance at the quarter wave point goes up to the area were
you do need a 4:1 or 6:1 balun. So the articles I found about not using
the balun were wrong.
I have a spare 4:1 balun so will be planning a Spring install of a long
wire 6m antenna.
73, Tom n4zpt
Tom Azlin, N4ZPT wrote:
> Hi Bob,
> Well, with a half wave the quarter wave point is 72 ohms. With a
> resonate antenna it should be resistive no matter where you check. When
> you stack more half waves the end effect shifts the minimum impedance
> point but there should be a place where it is back to 72 ohms or such.
> Ground effects would I thought reduce the impedance. Sounds like a
> question for Mike Toia, K3MV, our local antenna engineer.
> I guess we can just make them and then try it both ways. Is there a way
> in the model so search for the low impedance point and see what it turns
> out to be?
> Mike - we are looking at making a long 6 meter antenna of perhaps 6 wave
> lengths or more. And feed it from a good point. I was thinking that a
> quarter wave in it would be back to a low impedance not much different
> than feeding a half wave in the center. But modeling it gave 400 ohms or
> so. We are operating monoband. What would you say here?
> Thanks and 73, Tom Azlin n4zpt
> Bob Bruninga wrote:
>>> If you are using it only on 6 meters then you do not need to get an
>>> impeadance transformer. Just hook coax directly to the wire a
>>> quarter wave from the end away from where you want the gain.
>> But when I modeled it on EZNEC, I get about 400 ohms at that point.
>> Yes, it is mostly resistive, but it is around 400 ohms. Hence, I
>> don't need a tuner or matching system other than just an impedance
>> transformation that I can simply do with 1/4 wave of about 140 ohm
>> So to get 140 ohm line, I am trying to remember the trick o using two
>> lengths of 70 ohm line... but dont remember what to do with the
>> Bob, Wb4APR
More information about the Tacos