These opinions re changing bandwidth of an antenna by adding or subtracting
feedline are the silliest things I have heard in a long time. Tom, and many
others, are correct in that making bandwidth broader by adding feedline is
only introducing loss. Saying it has done something magical is on about the
same level as saying you can change the SWR by playing with feedline
lengths.
Ideas about correcting impedance mismatches, and etc, beg the point because
nothing has really changed at the antenna. You may fool a meter at the
input to the line, but you have not really changed anything about the
antenna.
I remember an old quote from QST, long long ago when I was much younger.
The author's name escapes me at the moment, but he was a well-known QST
editor. His statement was very simple: "The only thing that changes SWR on
a feedline is the load at the end of the line". This is pretty basic, and
the facts have not been repealed either by modern electronics or by
modeling.
SWR is not directly related to bandwidth, of course, but I refer to it here
only to emphasize my point about weird misconceptions. One thing modeling
will definitely do is give you a pretty good idea of how the bandwidth curve
will look for a given antenna. If you can go outside and change the
feedline length and create a better curve, and think something good has
happened, then you had better get the ARRL Anenna Handbook out and start
reading.
Wes - N5WA
-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com]On Behalf Of K3BU@aol.com
Sent: Wednesday, October 10, 2001 7:56 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Re: Force12
In a message dated 10/10/01 8:21:01 PM Eastern Daylight Time, w8ji@akorn.net
writes:
>
> The only mechanism that increases bandwidth is loss in the line.
> Nothing else.
> 73, Tom W8JI
Here is one "else":
Quarter wave "bazooka" coax balun increases the bandwidth. Change in its
reactance with frequency works "against" reactance change of antenna with
frequency.
Yuri, K3BU
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
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