Cat5 impedance (for each individual pair) is supposed to be 100 ohms.
Note that there is cat5 out there of questionable quality just like for
coax, but you're usually OK if you stick with the major brands.
The baluns you're talking about sound like the ones I've frequently seen
used for security cameras. They basically convert from a 75 ohm BNC
(usually from RG59) to a single pair of "cat5". They do work, although
they aren't as good as "real" coax (at least for the video application).
Cat5 is also going to have issues when close to metal objects similar
to, but less pronounced than, ladderline.
There are fancy baluns that can send VGA signals over cat5 although I've
never used one. If you need to use multiple pairs in the same physical
cable, you might be better off using cat6 instead of cat5. Cat6 is very
similar to cat5 aside from two major differences:
1 - cat6 usually uses 23 AWG wire instead of 24 AWG, so it should show
*slightly* lower loss
2 - cat6 has a plastic separator (it looks like a "+" from the end) that
keeps the twists of the pairs from pressing into each other.
I would expect the separator to help reduce crosstalk between the
individual cable pairs for RF just like for data. The very slightly
heavier wire gauge -- and not all cat6 is made this way -- probably
won't make any noticeable difference in loss, but it might allow you to
send more DC down the line for controlling remote switches, amps, and
the like.
-Bill
[snip]
> These leads me to another question of using CAT 5 cable for feeding
> Beverages. It is balanced, cheap, and some are even designed for self
> sealing and shielded versions for direct burial. The reason I ask is
> that a similar balun, but designed for long runs of CAT 5, is also
> available in a special on line flyer for $10 each if you buy four of
> them. The MCM part is 50-7725 with source Code DD1252. (sale ends
> midnight May 14, 2012) These baluns are designed to send two separate
> audio signals using CAT 5 up to 1000 feet. The unbalanced inputs are
> RCA connectors and the CAT 5 is a RJ-45. Since the wire in CAT 5
cable
> is a series of twisted pair, and used for years for longer runs of
> balanced pair audio and video, perhaps they would have a suitable
lower
> cost application of feedings Beverages and Two wire reversible
Beverages
> some distance away from the shack and tower. I have yet to be able to
> find out what the impedance of a single twisted pair is on CAT 5
cable.
> Nor do I know if these baluns double up on pairs.
>
> There must be a downside to this suggestion or I would have heard some
> comments of the A/V balun used for TB RX situations by now. So I pass
> this along regardless as someone may have had an chance to try them.
>
> Herb Schoenbohm, KV4FZ
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
|