[TowerTalk] Was: Open wire line convert
Tue, 19 Sep 2000 09:46:50 -0700
A brief (maybe) follow-up..
The main object of most of what I have written is to inspire the reader to
_think_ about what he is doing, rather than accept "conventional wisdom."
The cable length example I concocted was only that; an example. I wanted
the reader to think about the ramifications of pruning the line length and
then make a decision about the "goodness" of that technique. In the
example cited, I don't believe it makes any practical difference whether
the line is pruned or not.
Neither do I think that ladder line is totally impractical for a lot of
applications. It certainly has its place in the list of options. The
reader must decide on the suitability for each application. My goal was to
supply information to assist in an informed decision.
For those who have Mathcad, a worksheet that implements the equations used
in the ladder line paper and that I used in the earlier example can be
Similar calculation aids are Dean Straw's programs "Tl" and TLA"
At 08:09 AM 9/19/00 -0600, Dave D'Epagnier wrote:
>After reading Wes's web page and article, I don't think he is indicating
>that open wire feeders are always inferior to coax. He is merely stating
>that the plastic insulated types don't perform well when wet and that under
>some conditions baluns and tuners in the system can end up eating a lot of
>power which is often overlooked. There are some conditions where none of
>these problems exist. I have a friend who has a 40m bi-square (roughly 1200
>-j1200 ohm input impedance) centered at 100' in height with a home brewed
>open wire feeder with air dielectric. He uses a (balanced) Johnson Matchbox
>between it and his amplifier. This combination performs fine under wet
>conditions and is easier to match than a 50 ohm feeder with this antenna,
>and has less loss (although probably negligible at 7.15Mhz).
>> -----Original Message-----
>> From: w0hh [SMTP:email@example.com]
>> Sent: Tuesday, September 19, 2000 5:47 AM
>> To: firstname.lastname@example.org; email@example.com
>> Subject: Re: [TowerTalk] Open wire line convert
>> Thanks Wes, for revealing the ugly truth about "open wire" feeders. I
>> thought this stuff belonged back in the 1930's. And I thought it had died
>> well deserved death right after WW2, when coax became widely available,
>> most rational people switched over. I don't think you can beat a good
>> quality coax cable, especially if a good performing tuner is used, when
>> needed. These modern tuners, such as my ATR-30, sure are hard to beat.
>> 73 Tom W0HH
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