Home cinema - OTA Antenna - trying to get smarter

-hh wrote:
Alan F wrote:
That zip code is definitely at deep fringe range from the Philadelphia
stations at ~78 miles and Baltimore at ~73 miles. There are 3 Salisbury,
MD stations to the south for PBS, CBS, ABC. There will be 2 VHF stations
in Philly after the analog shutdown: as you listed, WPVI-DT ABC 6 on low
VHF 6 and WHYY-DT PBS 12 on VHF 12. The rest will stay on UHF. BTW,
WBAL-DT NBC 11 and WJZ-DT CBS 13 in Baltimore will switch to VHF 11 and
13 in February, 2009 if you parents can get the Baltimore stations with
a rotator.

There's also an obscure Atlantic City station (PBS?) that they get at
times. I do know that they have a rotor for their existing antenna,
but they're not using it much at all anymore (they're simply making
due with fewer channels). A multi-directional system that eliminates
the need for a rotor would be a 'nice to have', but my understanding
of these is that they require each channel to be individually
filtered, which gets complicated, etc.

A multi-directional antenna setup with filters for 70+ miles can get
rather complicated, expensive, and really requires that person who has
it knows how to maintain or tweak it.

But because of WPVI-DT, your parents will need full VHF and UHF
antenna coverage. If their current antenna works, I would give that a
try to see what digital stations you can get with it.

"Test with current, then adjust" is exactly my plan.

If the antenna has
been up there for years, the co-axial cable may be RG-59 or even twin
lead. If so, I would replace the cable with quad shielded RG-6 before
replacing the antenna if you get most of the digital stations. RG-59 has
measurably higher loss per foot for the high UHF channels than RG-6, so
RG-6 is strongly recommended. Even if the cable is RG-6, if it has been
exposed to the elements for years, check the cable for cracks and
connections for corrosion. Moisture can seep in through the cracks and
act as an attenuator.

Its an old enough installation that it has to be RG-59 (at best).
Replacing the exposed-to-outdoor cable is a no-brainer, but when it
comes to cable that's indoors _and_ downstream of the amplifier, is
there that much of a benefit or not? I'm not sure how easy/hard it
will to replace the wiring inside the house, as I'm not sure of the
cable run - it very well may have been moved to be inside of walls,
etc, over years of renovations.

Does your parents antenna setup have a pre-amp?

I'm almost positive that they have an amplifier somewhere, but I don't
know how physically close it is to the antenna. Obviously, the closer
to the source, the better.

Looking at the antenna photo you provided, your parents antenna
appears to be a Channel Master 3678 Double Boom which a good deep fringe
antenna. Underneath the antenna on the mast is a rectangular black item
which is probably the pre-amp. Then the cylinder further down the mast
is probably the rotator. I would keep this antenna setup if it is not
too corroded. If you can get up there, look at the pre-amp for
corrosion. If it needs to be replaced, the Channel Master 7777 pre-amp
would be a logical choice for their situation.

If the cable is RG-59, you want to replace as much as it as you can.
Although if you can get all of the Philadelphia digital stations and who
knows the Salisbury stations from the backside, you may want to leave it
alone. But as to why replace RG-59, check this website, which is very
useful for antenna info:
http://www.hdtvprimer.com/ISSUES/erecting_antenna.html

Under antenna basics, look at the chart under Tranmission cable titled
Cable loss in dB per 100 feet. RG-59 has 2-4 dB higher loss per 100 ft
at UHF channel 50 than RG-6. RG-11 is still better, but RG-11 is pricey
and so thick as to be hard to bend:
http://www.hdtvprimer.com/ANTENNAS/basics.html.

If you replace the antenna, the optimum approach for deep fringe range
setups is considered to be to use separate antennas for VHF and UHF. Any
combined VHF/UHF antenna has design compromises to cover the 3 very
different bands. A common deep fringe setup is to use the AntennasDirect
91-XG for UHF (http://www.hdtvprimer.com/ANTENNAS/XG91.html) and a VHF
only antenna such as a Winegard HD-5030. But if you want to keep it
simpler, then the Winegard HD8200P is considered a excellent deep
fringe, albeit a very large antenna. Reportedly the HD8200P is being
replaced by the HD8200U which can be shipped via UPS as the HD8200P is
too long for UPS.

Thanks; will keep this in mind. They're waterfront, so I'm also
concerned about wind loads (the current rooftop system has guy wires
to keep it from torquing its mount), although I can see how two
"medium" antennas might be better than one "huge".

The separate antennas for UHF and VHF can require more maintenance and
wind load issues. They may be better off with a single sturdy deep
fringe VHF/UHF antenna setup.

Alan F