[TowerTalk] 30/40/80 DIPOLE (balun/strain relief ideas needed)

[Mark .]

Pete wrote:
<< I'm shopping for a 40/80 dipole for my Mom (KF4VMT) and have been 
studying one of the Hypower models. It has an SO238 connector at the 
feedpoint and I wonder what kind of balun I could buy that would mate with 
this? I could make a custom bead balun but am very short of time and want to 
build rather than buy. Does anybody make a bead balun with double SO238 
connectors (or ideally, one PL259 and one SO238)? I also need to arrange for 
strain relief for the coax below the balun (and double PL259 if I use that 
to connect the balun). Taping some dacron cord to the coax and tying the up 
to the antenna feedpoint (which has
an eye hook in it) is the best idea I can come up with. Any better ones?

Regards,
Pete
KS4XG >>

Hello Pete,
First of all, congratulations are in order for her recent upgrade to Extra 
class (way to go, Mom!).
Looks like you have multiband operation in mind, and I am absolutely certain 
she will want to operate much more than on 80m and 40m, since she is 
interested in DX (per QRZ.com info).

You could get a combination center insulator/balun, such as the Radio Works 
(http://www.radioworks.com/) BK-1, with separate, resonant dipoles cut for 
40 and 80 connected with common feed point. This gets you 2 bands, 50 ohm 
feed, tunerless operation, and you are done for 40 and 80.
Downside: This will make your center feed point very heavy and unwieldy 
unless you have a center support rope for your dipole. And, you would be 
stuck using a coax feedline, which compromises performance when using the 
dipole on bands other than 80 and 40.

Your absolute best bang for the buck is an 80 meter doublet (homebrew) , 
strung up in a flat-top configuration, and fed with parallel wire feedline, 
such as 300 ohm tv twinlead (very cheap and light) or 450 ohm 'ladder line' 
(much stronger and durable). This requires either:
1) A tuner in the shack having open wire outputs, or
2) A remote 4:1 balun, located at the entrance to the shack, such as the 
Radio Works "remote balun", a coax jumper, and a tuner with coaxial output.
This gets you 80-10m, with multiple lobes of gain on the higher bands 
approaching modest beam capabilities, a very light assembly that is easily 
suspended from the ends, and sheds the wind.

Note: there are other places that sell balun/insulators, and you certainly 
don't need the 2KW rating of the heavy, Radio Works models.

I have a plan sketched up for one method of construction at:
http://www.qsl.net/n1lo/80mdblet.pdf

Have fun Pete and Mom!

--...MARK_N1LO...--
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