Cat 5 as Antenna cable
Darren Gardner
Does anyone know if it is possible to use Cat 5 as Antenna cable?
If it is possible how do i match the impediences, etc....
Thanks
Darren
Executive
and Datatwist (350) series also BICC Gigatwist and others. Baluns
available for 75 to 100 ohm from a number of US sites - possibly 50 ohms
as well.
Peter Messer
pme...@camtech.net.au
Peter Jetson
> Does anyone know if it is possible to use Cat 5 as Antenna cable?
As an antenna cable for what, exactly? Transmitting? Receiving?
Both? Over what frequency or frequency range?
Peter
Darren Gardner
Darren
Darren Gardner wrote:
> Hi
> Does anyone know if it is possible to use Cat 5 as Antenna cable?
Peter Jetson
> Sorry I should have said TV antenna type cable.
Probably the best type of antenna to make out of pieces of wire is a
folded dipole. You can see a diagram of one at
http://n-lemma.com/antenna/index.htm just so you know what we're talking
about. Usually, they're made out of flat 300 ohm TV ribbon cable, and
besides making your own, you can buy them at Tandy or similar places for
a few bucks. I've even seen a makeshift folded dipole antenna made from
speaker wire!
If your TV has a 300 ohm antenna input, you can connect a folded dipole
made from 300 ohm ribbon cale straight into it. If your TV has a co-ax
connector, you'll need a balun (which converts the 300 ohm balanced
antenna to 75 unbalanced co-ax). These are *also* a few bucks from an
electronics store.
Now, with the description out of the way, let's get down to business.
The main problem is that you want to use cat 5 cable, not 300 ohm TV
ribbon cable. The trouble with using cat 5 cable is that the four pairs
of wires are *twisted pairs*, and the reason they twisted is to *stop*
them picking up external signals - the exact opposite of what you want!
And, to make it worse, the four pairs of twisted wires are then also
twisted together, so you can't really use any of the wires.
So, I'm afraid the best you can do with cat 5 cable probably isn't going
to be good enough to actually work any better than just connecting a
random length piece of wire to your antenna terminals.
Perhaps if you explained *why* you want to make an antenna out of cat 5
cable, I could come up with other suggestions.
Miro Jucevic
Cat 5 cable is 100-Ohm differential signal cable with 4 pairs.
Coax TV cable is 75-Ohm shielded solid core cable.
(300-Ohm TV cable is option, these days you can get an aerial mast balun
that runs 75-Ohm all the way)
Only AT&T manufacture a low end product (with limited success for TV) which
is able to be used at each end of the CAT 5 and thus enable the use of Cat5
for TV.
Many schools had the same problem think ing that Coax was dead went and blew
the budget on Cat5 and then tried to get the TV's in the place to work using
Cat5.
That's not the same problem as you have stated, but it is the only likely
use for Cat 5 in TV.
In a nutshell, speak to Matchmaster in Sydney about the cable you need. They
have all grades and prices.
Darren Gardner
Thanks for your reply. I dont actually want to make the antenna out of
Cat 5 cable. I want to use the Cat 5 as Antenna cable (ie between the
Antenna and the TV). Sorry if I confused you. Can I do this? Do I need
balan's or something to balance the impedances?
Thanks Again.....
Darren
Peter Jetson
> Thanks for your reply. I dont actually want to make the antenna out of
> Cat 5 cable. I want to use the Cat 5 as Antenna cable (ie between the
> Antenna and the TV).
Whoops - I spent so much time on an answer to a question you didn't even
ask :-(
> Sorry if I confused you. Can I do this? Do I need
> balan's or something to balance the impedances?
Simple answer, yes. Long answer, it's probably not all that likely to
work very well even if you *could* easily buy or make the two balun 100
ohm to 75 ohm (or 100 ohm to 300 ohm) you'd need to match the impedance.
You only need the one twisted pair of wires to bring the signal down
from the antenna, and cat 5 cable has four pairs, all twisted together,
which is likely to affect how well it'll carry the signals. Cat 5 cable
also isn't designed to handle the frequency range of TV signals.
Having said that, though, why haven't you just tried it? I've seen
crazier things actually work in practice. Your antenna most likely has
a balun in it already, so remove it and connect a pair of cat 5 wires to
the terminals that are left. Then, use the balun you removed from the
antenna down at the TV end of the cable to convert the balanced pair of
cat 5 wires back to unbalanced to connect it to the co-ax input of the
TV.
It'll either work well enough for you, or it won't. Pretty simple
choice.
Peter