Ulrich and others that have inquired. Ther is no velocity factor involved
with the sleeve balun. The coaxial feedline has no effect. The sleeve
balun is like an element of the antenna and is cut according to the normal
antenna element formula. It's response is relatively broad and being within
a 1/4" at the 70 CM frequencies makes the balun respond properly over the
entire 420-450 mHz. At HF the length of the balun is not critical at all.
Here is my reply to one reflectoree regarding my method of getting the
length correct.
"I just make the braid a little long to start and make the measurement on
the
coax feedline to where I want the sleeve tied in. I bare the braid for
about 1/2" on the coax and solder the sleeve.
Then I start taping at the shorted location compressing the braid as I go
towards the feed point. When I get to the feedpoint, I cut off any extra
sleeve braid, solder a small wire around the entire braid to make a good
solid ending connection, silicone it and then tape over that.
I generally leave about 1/4" between the end of the sleeve balun and the
braid and center conductor connection going to whatever antenna element."
No, Ulrich, I have never measured the resonance of the sleeve baluns. Never
had a reason to.
Some of you may be familiar with a commercial version of the sleeve balun
which was manufactured by and sold by KLM to be used with all of their 70 CM
and 2 Meter multi-element directional antennas back in the 70's. They used
copper tubing for both the coaxial cable and the sleeve, with teflon
dielectric. Worked very well but were expensive.
Good luck to all de Milt, N5IA
----- Original Message -----
From: "Ulrich Weiss" <dj2ya@t-online.de>
To: "Milt Jensen, N5IA" <n5ia@zia-connection.com>
Cc: "Top-Band Reflektor" <topband@contesting.com>
Sent: Saturday, December 20, 2003 8:26 AM
Subject: Re: Topband: FERRITE BEADS
> hi Milt,
>
> I've read your contribution with great interest, as I have done the same
on
> my quad feedlines in the past... I'm surprised that you do not consider
the
> velocity factor of the vinyl jacket of the actual feedline coax that is a
> dielectric in the sleeve.. I remember that I had to do a number of
> experiments to obtain a resonant quarter-wave sleeve... have you ever
> measured the resonance of your sleeves???
>
> the Compliments of the Season
>
> Uli, DJ2YA
>
> ----- Original Message -----
> From: "Milt Jensen, N5IA" <n5ia@zia-connection.com>
> To: "Tom Rauch" <w8ji@contesting.com>; <w0vd@sofnet.com>;
> <Topband@contesting.com>; "Earl W Cunningham" <k6se@juno.com>
> Sent: Saturday, December 20, 2003 5:12 AM
> Subject: Re: Topband: FERRITE BEADS
>
>
> >
> > ----- Original Message -----
> > From: "Tom Rauch" <w8ji@contesting.com>
> > To: <w0vd@sofnet.com>; <Topband@contesting.com>; "Earl W Cunningham"
> > <k6se@juno.com>
> > Sent: Friday, December 19, 2003 2:46 PM
> > Subject: Re: Topband: FERRITE BEADS
> >
> > SNIP
> >
> > > The cheapest way to make a good balun is still an air core winding of
> > coax,
> > > assuming you have the room and weight isn't a problem. If you want to
> save
> > > space or weight, something like a 65 material with multiple turns is
the
> > > next choice.
> >
> > SNIP
> >
> > > 73 Tom
> >
> > My solution, relatively inexpensive but quite time consuming at the
lower
> > frequency bands, is to use 1/4 WL open sleeve baluns. I use these on 70
> CM
> > and 2 M directionals in quantity on our VHF and UHF mountaintop systems.
> I
> > have constructed them to use on 10 M and 6 M vertical wire dipoles used
by
> > our mountaintop remote controlled base stations. I use one on the 20
> Meter
> > monobander as well as the 40 Meter monobander and the 80 Meter dipole
her
> at
> > the home QTH. AND I have one constructed for use with a portable 160
> Meter
> > dipole that I carry around to temporarily string from tall towers.
> >
> > I strip the 95% braid from older RG-8 or RG-11 and sleeve it over the
> > feedline for a 1/4 WL and solder it to the braid of the coax at that
> point.
> > The sleeve is open at the feedpoint end of the coax. I typically cover
> the
> > entire length of the braid with black tape after sealing the two ends
with
> > silicone.
> >
> > I must admit that the 160 M model was quite a chore. Sleeving 125' of
> braid
> > over the feedline and then taping it all down is NOT a single night
> project.
> > However, the results are superb. No additional losses from extra length
> of
> > coiled coax or a heavy coil to hang somewhere. No beads to heat or
worry
> > about. I certainly don't own the patent for the design but I suppose I
> have
> > constructed a hundred or so of these over the past 25 years. Never a
> > failure and 100% performance.
> >
> > Happy holidays de Milt, N5IA
> >
> >
> >
> >
> > _______________________________________________
> > Topband mailing list
> > Topband@contesting.com
> > http://lists.contesting.com/mailman/listinfo/topband
>
>
>
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