| MadSci Network: Engineering |
It's just about impossible to predict how well one of these gadgets would
work for you. It is true that your house wiring acts as an antenna; any
piece of wire will. However, that does not mean that the house wiring is a
GOOD antenna that provides a CLEAN signal. What the device does is pass
any TV signals picked up by the wiring to your TV or VCR while blocking the
household AC current. What the device will also do is pass along any
interference ("static") carried on the wiring, as well.
WARNING: Under no circumstances should anyone attempt to directly connect
their household electric wiring to the antenna terminals of a TV or VCR.
Damage to your wiring, damage to the equipment, a fire, electric shock, or
even death are the likely outcomes.
The problem is that the configuration of the wiring in your house is
unlikely to be a good antenna. The lengths of the wires are not matched to
the wavelengths of TV signals, and the directivity ("antenna pattern") is
not controlled or controllable, and impedance of this "antenna" is poorly
matched to free space. This meaning some stations may come in OK while
others don't come in at all or are subject to a great deal of ghosting and
fading, and there's nothing you can do about it.
Also, any electric motors in your house (especially for small appliances),
flourescent lights, and light dimmers are likely to generate interference
that degrades the TV picture (streaks and "snow"). This electrical "noise"
will is carried on the electric wiring and this device will pass it
directly into your TV or VCR along with the desired signals.
I've seen this things advertised, but for the same amount of money, I'd
simply go buy a pair of rabbit ears (that's what I use). You can get
fancier ones that include a signal amplifier, but a set in the $10-$20
range with a "channel selection" knob will work about as well as a set of
rabbit ears can work, assuming they're connected to anything other than the
very cheapest TV or VCR. This is because the amplifier in the tuner of
even a moderate-quality TV or VCR is likely to be better (i.e., have lower
noise figure) than the amplifier in a pair of rabbit ears.
Steve Czarnecki
P.S. #1 I'm assuming you don't live in a building with metal walls or a
metal skeleton (much commercial construction and an increasing amount of
residential construction uses galvanized steel studs rather than wooden
2-by-4 studs). If you do live in a building with a metal wall or metal
studs, only an outdoor antenna is likely to work well.
P.S. #2 An alternative to mounting an antenna outside is to mount it in
indoors (in the attic, for example), assuming you don't have metal walls, a
"tin" roof, or metal studs in the walls. In a wooden building, the antenna
will work just fine indoors. They're usually mounted outdoors simply to
get the highest possible vantage and becuase they take a lot of space.
Try the links in the MadSci Library for more information on Engineering.