I wouldn't use a 4:1 balun, (if you are converting to coax near the shack)
since the open wire feeder is likely to be terminated at the antenna end
with an impedance other than 400 ohm resistive. This will reflect back to
the transmitter end of the 400 ohm line and the impedance will not be 400
ohms looking into the line but will be dependent upon the antenna impedance
and the length of the 400 ohm line. There are some online calcualtors which
can determine the impedance the shack end if you enter the line
characteristics, antenna feedpoint impedance and feedline length.
A choke balun (current balun) would be a better way to go I think. The ideal
way to go would be to use a high power remote tuner at the antenna feedline
connection but the choke balun should be cheaper and give good results.
Mark N1UK
----- Original Message -----
From: "Edward Sylvester" <navydude1962@yahoo.com>
To: <TowerTalk@contesting.com>
Sent: Thursday, 01 January, 2009 2:55 PM
Subject: [TowerTalk] Unique Inv L...Help!
> What a great group! I have one more antenna curiosity for my second
> QTH....I work up north during the week and stay in my RV...I have the good
> fortune of having access to the tall pine trees (>100' tall). I installed
> two antennas....
>
> The first is a Cobra Ultralite Senior (140' linear loaded, fed with open
> wire line). This rivals some of the best antennas I have ever had. Tunes
> 6-160m.
>
> Because the span between trees is about 300', I decided to add a second
> antenna in series to take advantage of the set up. This second antenna is
> a LW with a total length of 300' or so.
>
> I have compared the two and I prefer the dipole. The LW couples into
> anything electronic and I hesitate to use it because it causes
> interference. It's also noisier and is virtually the same as the dipole,
> in terms of signal output.
>
> Hence, it's somewhat of a disappointment. Plus, my signal on 160m is
> anemic. Thinking I can convert this into an Inverted L for a better DX
> antenna.
>
> This would not be a resonant antenna for any specific band, as I don't
> know the exact length and I don't have access to the horizontal portion
> for pruning.
>
> I had to hire a tree climber to install these!! I just want to work with
> what I have...
>
> Here are my thoughts....Why not bring the vertical portion of the LW to
> ground level (about 100') and attach to non resonant radials?
>
> I can feed it with 450 ohm ladderline and terminate with 4:1 balun before
> feeding it to a wideband tuner.
>
> My question is, would I maintain the valuable characteristics of an Inv L
> and would this be killer on 160m?
>
> I currently feed this same LW into a remote balun, with an effective
> counterpoise on the other terminal lug. Only thing is that it's not a
> ground level and I have no radials, per se.
>
> Thanks for the bandwidth. As always, your thoughts are appreciated.
>
> 73 and Happy New Year!
>
> Ed NI6S
>
>
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|