Converting an unbalanced feedline to a balanced feedline

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wb3cez
Posts: 39
Joined: Sun Mar 21, 2004 11:11 am

Converting an unbalanced feedline to a balanced feedline

Post by wb3cez » Wed Feb 03, 2010 9:26 pm

I,am currently running an unbalanced coax feedline from a G5RV into an MFJ-994 autotuner. The tuner is also capable of tuning a balanced line but you can not have two different antenns connected to this tuner at the same time. My second antenna is an endfed which I would like to be able to switch to without disconnecting the coax line first. MFJ makes a MFJ-w9inn balun which will convert a 400 ohm balanced line to a 50ohm coax feed. The problem is my endfed, as a single wire feed, presents a 50 ohm impedence against ground. I suspect the w9inn balun will not work in this configuration since it wants to see 400 ohms. Anyone have any ideas on how I could convert the 50 ohm endfed antenna to an unbalanced coax feed? If this can be done, I would be able to switch antennas with an external antenna switch,

AE4SH
Posts: 81
Joined: Fri Aug 26, 2005 3:37 am
Location: cherryville, nc

Converting an unbalanced feedline to a balanced feedline

Post by AE4SH » Wed Feb 03, 2010 10:40 pm

i had a simular problem at one time.
i ran a coax out of the tuner to a switch with 3 antennas attached to the switch.
i had no more problems after that.
if i were you i'd get a good antenna switch and try that.

wb3cez
Posts: 39
Joined: Sun Mar 21, 2004 11:11 am

Re Converting an unbalanced feedline...

Post by wb3cez » Thu Feb 04, 2010 3:47 pm

Thanks for your reply. Perhaps I didn't state my problem as clearly as I should have. The endfed antenna connection I wish to run to the autotuner is a single wire, not a 400 ohm ladder lead or coax. This single wire needs to be terminated with a PL-259 in order to be able to run it thru an external antenna switch. I need some kind of a mathing device in order to do this.

k9yli
Posts: 227
Joined: Fri Aug 12, 2005 11:35 pm
Location: northwest wisconsin

Post by k9yli » Thu Feb 04, 2010 5:38 pm

for a single wire feed and pl259, just solder the wire to the center pin.
the rest will be taken care of in how ever you originally had it connected to the tuner..
its possible you would need two say 2 position coax switches to accomplish this.
one to flip flop between the so239 and the single wire connection on the tuner if it has one. the other to switch the input to that switch from multiple antennas..

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