31 Mar
2005
31 Mar
'05
2:11 p.m.
On Thu, 31 Mar 2005 14:38:07 -0600
Tom Peters <tpeters at mixcom.com> wrote:
I'm still looking for specs on thicknet cable-- I
know the
characteristic impedance is 50 ohms, but if I knew the velocity factor
and losses at VHF (144 - 148 mhz) and UHF (430 - 450 MHz) I could use
the stuff for my amateur radio hobby. As it is, it's gathering dust.
AFAIK
thick Ethernet cable is more or less RG213. Typical values are 8
dB / 100 m attenuation at 150 MHz and 15 dB / 100 m at 450 MHz and a
velocity factor of 0.66. So it should be good enough at least for VHF
and depending on length even for UHF. Many OMs use thick Ethernet cable
to connect short wave antennas. But make sure that the thick Ethernet
cable is unused when you put it outside. Water soaking into the cable
through old vampire tap holes is a funny failure to debug. ;-)
Ahh, and keep in mind that these cables usually are not UV resistent, so
sun light will destroy the outer jacket! Cover the cable if used
outside to avoid direct sun light.
I have a 50 m spool of Belden 9880 cable. This was special made for
thick Ethernet. It has 4 shildings (braid - foil - braid - foil) a foam
PE dielectric. Due to the extensive shilding and the same outer diameter
as RG213 the dielectric is thiner. So Belden used foam dielectric to
compensate this and get the same specs as RG213. I intend to use it to
connect my short wave antenna once I get my licence...
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/