[TowerTalk] BALUN revisited again

[Patrick Greenlee]

What I don't know about baluns would fill volumes.  I'm trying to help a 
fellow ham, even less knowledgeable than I (if you can believe that 
possible) but are running into a lot of confusion.

Here is the application of interest:

My friend is building a portable one man operable sectional mast (guyed 
when he uses enough sections to make it required) with an adjustable 
length horizontal dipole on top.  Recall in the olden days how 
automotive antennas were telescopic metal whips that could be manually 
lengthened and shortened? Well he has a pair of these ON STEROIDS.  They 
collapse short enough to make a 1/2 wave dipole for 6m and extend long 
enough to be a 1/2 wave dipole on 40 m.  They are robust stainless steel 
(yeah, I know not the best conductor) but they will survive his use and 
the weather.

I told him he needed a balun to interface the unbalanced coax feedline 
to the balanced antenna. ...and then massive confusion ensued...  he was 
sold something I have determined is not going to work.  I think the term 
balun is a description of what a device does but not how it does it.  
Anyway he will be running low power, i.e. no more that 100 watts and 
typically QRP.  I'm taking him with me to a ham fest departing for it 
before sun rise Saturday (day after tomorrow)

If someone could fill me in regarding what he needs maybe we can buy one 
then.

I have a UNIDILA balun that is coax in and flying leads out but his 
dipole arrangement has an SO-239 so he wants to connect the balun to the 
antenna via a double male UHF (double ended PL-259, I forget the 
number)  We can adapt as required, even flying leads to UHF connector.

Please tell me what the best couple choices are for this application and 
I'll try to steer him in the right direction.

Thanks for any consideration,

Patrick        NJ5G