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LETTERS TO HOME TOYS!
If you have comments or questions about the HTINews or Home Toys in general please send them along to me and I'll publish them here (and even try to answer them if I can). Send your letters to bobh@hometoys.com .
In one of your review articles on home wiring, there is a discussion about AC currents and EMF emitted from them. You speak of the need to maintain distance, but also address speaker wire and low frequency hum. My question pertains to running speaker wire along with coax (RG-6 quad shield) and CAT 5 all in the same bundle. Will there be any interference with this. Your article on low voltage cable says to keep a distance from coax, but yet many manufacturers are now bundling CAT 5, coax and speaker wire together.
Thank you for your info.
Bruce Weiner kweiner@luna.cas.usf.edu
Good question Bruce. I'm going to pass this on to Mark Henrichs the author of the article. He's much better equipped to answer than I am. ... Mark's reply follows.
First of all, I need to make it clear that I am no expert on the subject, and the
article was written based on results of the research I had done. I can not assume any
responsibility for consequences since I am not a professional in the field, and results
could vary depending on the installation and usage.
That said, my research never found any strong arguments that running low-voltage cabling
next to each other would cause a problem, as long as the proper quality cable is installed
properly. The coax cable, properly grounded, should shield the signal from outside
interference, as well as help shield surrounding cables from its own signal. Similarly,
the twisted pairs in both Cat 5 and quality audio cable protect against signal
interference. It is mostly the high-voltage sine wave nature of AC power (hum) that causes
interference when run parallel and close to the low voltage cabling.
The main exception to this is trying to run two sources through the same jacketed cable.
For instance, I found several recommendations that, for instance, you should NOT try to
use one pair in a single Cat 5 cable for phone and one pair in the same cable for LAN. But
one jacketed cable for phone running next to another jacketed cable for LAN should be OK.
It is mainly the tight coupling of the twisted pairs within the same jacket that could
cause problems, depending on the type of signal put through each pair. For example, if
phone was run in the same jacket as LAN, and you put a modem on the phone line, I would
not be surprised to find a noise problem with one or the other (or both).
To be safe, I kept even low level cables separated at least a bit for most runs, except
where they had to go through the same hole, for example. Even in the "bundled"
modular cable I've seen there is a 1/16th inch or so separation, if for no other reason
than the jacket insulation thickness between cable types. So, from my research, you should
be OK with parallel low-voltage cabling in normal situations with quality wire. I welcome
any arguments to the contrary, though!
Bob, you are welcome to post this to whatever group this question came from (I have not
seen it posted), as long as it remains clear that I do not claim to be an expert on the
subject, and the comments are just my opinions based on results of my research.
Hope this helps!
Mark Henrichs MEH0045@mcdata.com
