|[AMRadio] Re: Link coupling|
rbethman at comcast.net
Wed Sep 5 20:22:24 EDT 2007
A.R.S. - WA5AM wrote:
> On 9/5/07, D. Chester <k4kyv at charter.net> wrote:
>>> This brings up a thought I've had about link coupled tuners, of which I
>>> Of course I feed the 50 ohm coax to the link. The center to one side
>>> of the link and the shield (ground) to the other. What effect does
>>> the "link position" have on a tuner? I suspect the link position
>>> (mine is rotatable) would affect the matching impedance to the coax?
>>> Brian / wa5am
>> If you have a variable link on the antenna tuner coil, there will be one
>> and only one critical degree of coupling that will give a perfect matching
>> impedance to the coax (assuming that impedance match is within the range of
>> the tuner). Increasing the coupling will make the coax see too low an
>> impedance, and decreasing the coupling will make the load impedance too
> Thanks Don, that's what I thought, and have indeed observed.
> 73, Brian
Yep! That is "one" of the quirks with the BC-610 coil and link.
You can get yourself a pile of grief with these old girls! They have
some, shall we say "interesting" characteristics when you mess with the
link coupling - AND - watch VSWR.
Then again, she'll get cranky dependent on the antenna system too!
I 'try' and stay away from the BC-939, and use tuned dipoles. It gets
out on the air better for me. Some have great success with the "long
wire" and BC-939. I just do not have the house, property, and
orientation, (N,S,E, & W), for that to do much good for me.
Bob - N0DGN
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