Hi Mike,
Thanks for your note. I wish I could find my old issue! As I recall
the design, a larger inductance (more turns) will be needed on the lower
frequencies to obtain good balun 'operation'. This design actually does
behave as a 'bandpass' transformer. It is a short circuit at DC. It is
limited at the upper end by its self resonance (just like any coil).
The dimensions are from my notes wherein I referenced the article
directly so I think it is W6TC's version which I use for my tribander.
I have used the device on a G5RV which worked fine but I would not have
confidence that I had good 'balun' transformation on 80m or 40m.
Correspondingly, the version with more turns would probably not work
well at 10m or 15m. I defer to W6TC's discussion which, as I remember,
noted his measurements of different designs.
In the meantime, I'll dig through my stuff and see if I can find any
more information. Now my engineering instincts have been piqued!!
73, George W1ZT
nasfred@interserf.net wrote:
>
> Hello George,
>
> Thanks for bringing to our attention the balun - dug out the Mar. '80 issue
> of HR.
>
> How low in freq. does your adjustments in length of the coax and wire allow
> the balun to function?
>
> In the George Badger's, W6TC, article his is designed (used twice the wire
> lengths you used) for use on the low bands - 160 thru 40ty - with hook-up
> wire for the second winding. Looking for a balun to use with a used TH6 I'm
> refurbishing.
>
> Thanks again, George, for bringing up a design and solution that is timeless.
>
> 73,
> Mike, K4GMH
>
> At 06:52 PM 11/18/97 -0800, you wrote:
> >RSOLOMON@systems.TEXTRON.COM wrote:
> >>
> >> Since I am taking the 402BA down to rebuild, I might as well replace
> >> the coax (Preventative measure). The Collins Coaxial balun interests
> >> me. Not having a CQ library, can anyone provide more info on this.
> >>
> >> Thanks, Dick, W1KSZ
> >> rsolomon@systems.textron.com
> >>
> >>
> >I use the version from Mar '80 HR for a 50ohm 1:1 balun as follows:
> >
> > RG 8X 50" long
> > #12 insulated wire 50" long (I use the plastic covered stranded)
> >
> > The coax and wire are COUNTER wound into a coil of 4.5" dia to make a
> > 3
> >1/2 turn coil of each piece. This means that the coax is wound
> >clockwise and the wire counter clockwise with it. The #12 wire attaches
> >to the shield of the coax at one end and then attaches to the center
> >conductor of the coax at the other end. I tape the whole thing
> >together.
> >Put a coax connector on the same end that the #12 wire attaches to the
> >shield. The antenna (balanced load) connects at the other end to the
> >coax shield for one line and the center conductor+#12 wire junction for
> >the other line. A picture is better. I hope this helps. The artcle
> >was excellent, I have successfully used these things since 1980 under
> >high power and SWR conditions.
> >
> >My power tests and SWR test show it flat to about 35MHz. I check my
> >recent one with the MFJ analyzer with similar results and I also noted a
> >self resonant frequency around 47MHz. I use it on dipoles and my Wilson
> >System 1 through 10 meters.
> >
> >Good luck.. George W1ZT
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