[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: RG-6 quad shield for 72 ohm cable and other antenna questions



Hi Luc, VE2DWE

34" long from tip to tip of the pl-259 is correct for the velocity factor of
a foamed RG59U coax cable.

The velocity factor of  a RG-6 is 0.659 (solid polyethylene dielectric)
so that the total lenght from tip to tip of the pl-259 through a T connector
at 145 MHz is 26.84 inches or 68.17 centimeters

Much better to use N connectors.

I got nice results even soldering directly the inner conductors and the
braids of the above maching lines provided the tips are very short and
the braids are directly soldered over the copper surface of a small piece
of PCB i.e. G-10 or any other material.

A protection of clear silicon over the soldered points is recommended
against water and pollution and it worked well to me for many years.

73" de

i8CVS Domenico

----- Original Message -----
From: "Luc Leblanc VE2DWE" <lucleblanc6@videotron.ca>
To: <amsat-bb@amsat.org>
Sent: Thursday, December 29, 2005 12:12 PM
Subject: Re: [amsat-bb] RG-6 quad shield for 72 ohm cable and other antenna
questions


> Hi
>
> I'm using two piece of RG59U foam type of 34" long from tip to tip of the
pl-
> 259! through a T connector and i got swr better than 1.5 on two meter.
>
> Hope this will saved you too much cut and try experiment as i do here...
Let me
> know if you can replicate my results with the 34" length.
>
>
>
>
>
> > Michael,
> > If you offset the two antennas as you mentioned, that will give you the
90
> > degree phasing for circular polorization. You only need to keep the
phasing
> > ( length of coax) equal between the two antennas for 0 phase shift.
> >
> > The second part of the problem is getting half the power to each
antenna,
> > this is done with a power divider.
> > Lines in 1/4, 3/4, 5/4 etc wavelengths will transform impeadence. You
must
> > connect two 50 ohm antennas to a 50 Ohm coax, so one solution is to use
two
> > 1/4 or 3/4 wavelength coax of 72 ohms to make each antenna 100 ohms and
both
> > in paraell will equal 50 Ohms. Using 72 Ohm comes out to be 103 OHms (
> > square of the coax matching section divided by the impeadence of the
> > antenna, equals the impedence at the other end of the coax.
> >
> > CATV cable is usally a foam type and the Vp varies dependent on the
foam,
> > and any deformities in the cable.  The solid polyethlene (Vp .66)
dielectric
> > is durable, and stands up better to weather, and is harder to pinch with
> > cable ties etc.
> > Caculation is a good  method with polyethlene cables, foam types are
better
> > measured and extreem care must be used in handling foam type cables.
They
> > are easly deformed.
> >
>
> >
> >
> > > I'm trying to homebrew  a crossed yagi array for 2 meters and since I
have
> > > a
> > > bunch of RG-6 quad shield cable lying around here from when I had
> > > sattellite
> > > TV, I'm wondering if I could possibly use it for the matching/phasing
> > > harness
> > > or do I need some other type of 72 ohm coax? I plan on offsetting the
> > > elements
> > > a quarter wavelength on the same boom. I've been reading the Satellite
> > > Handbook and I'm still a little confused about measuring the
electrical
> > > length
> > > of the matching/phasing lines. I looked up the velocity factor of the
> > > cable
>
>
>
> "-"
> "It is not the class of license the amateur holds, but the class of the
amateur
> that holds the license."
>
> Luc Leblanc VE2DWE
> AMSAT 33583
> Skype VE2DWE
> www.qsl.net/ve2dwe
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home