[AMRadio] Re: new antenna and matchbox a bust.


John Lawson jpl15 at panix.com
Tue Jan 30 17:12:58 EST 2007



On Tue, 30 Jan 2007, ne1s wrote:

> So what's not balanced?


   Given two lengths of coax, connected as per the Original Description - 
center 'hot', shields connected at each end and grounded:

   Resistively - perhaps at dc-to-some-very-low-frequency - this 
configuration will handle a 'balanced' circuit, in which both conductors 
are 'hot' and both are referenced equally to ground.

   As the frequency increases, the lumped-constant parameters of the device 
as a whole comes into play - just what kind of play, I haven't a good idea 
(yet).  Also - this is a fairly complex transformer, IMHO.

  And while I'm not sure if parallel-adjacent coaxial cables retain the 
characteristics we call 'balanced' at HF RF freequencies - its for Damn 
Sure that terminating this device in a balanced-output antenna tuner on 
one end, and in a run of classic ladder-line (of some signifcantly other 
impedance) at the antenna end - all this forms some kind of complex 
transformer / attenuator / network - the exact electrical nature of which 
I haven't the skills to accurately infer at this moment.

   I do know it's probably not "optimal".

   I also know that if, as a classic 4-terminal black box, you like what 
comes out as a result of what goes in... and 'not blowing stuff up' is a 
part of "like" - then I'd be of the opinion that It Ain't Broke.

   So don't fix it.....   ;}


   Someone did an article in QST sometime in the last 20 years or so - on 
pretty much the same subject. They decided to do the opposite of careful 
and scientific antenna design.  They used some small rig and a tuner and 
set about seeing just how many Things (of all descriptions) they could get 
to load-up - and have a QSO thereupon.  They talked on a table lamp 
(unplugged from the wall, natch) - a chain-link fence, an actual 
screwdriver, a wire coat-hanger, ect ect.   The moral of the story was 
just as others have said - if it works, it works.  If you're happy with 
how it works, well, cool!

   If on the other hand, getting an antenna system 'perfected' is your goal 
- that's an enjoyable part of the Hobby, as well....


    My 200 millidollar....


Cheers

John
KB6SCO
DM09fg






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