[AMRadio] new antenna and matchbox a bust.

w4rl at bellsouth.net w4rl at bellsouth.net
Mon Jan 29 15:39:21 EST 2007


Yep, that length of VN era comm wire is the longest string I've ever raised here, but it fits.
Going to the loop design I know did this:  My Antenna Loading Control capacitor is now fully meshed while tuned to 160, 80,and 40 meters.  I use about all the inductor on 160 though.  On 80 and 40 the inductor uses but a 1/4 of it's range of inductance.  Antenna pattern, well I know something has changed (I know, well duh), It seems to be able to "hear and talk further".  The fully loaded antenna loading capicator speaks for that ie getting more fire into the wire.  My run of the mil off the shelf 1:1 tuner has never burned up, and the 10 feet of 213 coax had not given me any apparent problems.  In fact, I did that design (getting the feedline throught the wall) by the suggestion from an engineer at one of the commerical manufactures of balums, antenna phasing units and such.  They advertise every month in qst.  Told me to specifically use a 1:1 at first attempt.  And if it did not self distruct to stick with it and use the minumum amount of coax between the balum and tuner.

Robert W4RL

> From: Brett gazdzinski <brett.gazdzinski at verizonbusiness.com>
> Date: 2007/01/29 Mon PM 01:34:43 CST
> To: 'Discussion of AM Radio in the Amateur Service' <amradio at mailman.qth.net>
> Subject: RE: RE: [AMRadio] new antenna and matchbox a bust.
> > Brett, my food for antenna thought.
> Thanks, I like to eat!
> > 
> > Having 40 feet of balanced line to a center fed 100 footer 
> > may be a bit too much to ask of the tuner.
> > I am assuming the tuner is the Johnson Matchbox (250 watt?).  
> Yes, and I suspect that is correct, I seemed to run out of range
> on the tuner as the swr was coming down.
> >  For 80 and 40 meters, I have found success using at least 
> > 125 feet fed at the center and at least 60 feet of balanced 
> > line.  The balanced line at the radio end is terminated to a 
> > 1:1 balum from which 10 feet of RG-13 goes to the unbalanced  
> > output SO-239 on my RF Power Components "Maxi Tuner" of the 
> > Lew McCoy Ultimate Transmatch design.  The 10 foot length of 
> > coax allows me to pass throught the shack's wall with all my 
> > other antenna feedlines.  Recently I extended the antenna 
> > into a horizontal loop (rectangle) which measures 120 by 60 
> > by 120 by 60.  It is still fed at the center of one 120 foot 
> > leg, and the other/opposite 120 foot leg is open at its 
> > center.  The antenna will tune 160 meters with ease, along 
> > with 80 and 40.  I did extend the feedline to a total length 
> > of 110 feet.   Of note, I live in a subdivision and have a 
> > lot size of approximately 90 by 140 feet.  Hope this 
> > information may be of some help to yo
> >  u with your situation.  
> Did going to the loop design improve things?
> That is a lot of wire!
> Brett

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