In article ,
Jimw wrote:
On Wed, 07 Jan 2009 22:21:22 -0800, Don Bruder
wrote:
In article ,
Robert Neville wrote:
Jimw wrote:
By the way, are there any decent antenna amplifiers for DTV, or does a
person just use the standard UHF VHF amps they always sold?
There is no difference between the analog and digital signal for antenna
or
amplification. Anyone selling "digital" is selling snakeoil.
Correct so far.
The only difference would be for those who are using a VHF only antenna
today
and have digital transmitters that are going to stay in the UHF band.
Partly correct, but for exactly the opposite reason you think. VHF
antennas will indeed become essentially useless. However, this is
because *ALL* digital transmitters are already on UHF (though some are
operating at lower-than-licensed power levels) and will stay there. When
the VHF signal is turned off in February, the VHF antennas will still
function as (lousy) antennas, but performance is likely to be so poor
that they won't be useful except in cases where there are very strong
signals.
So, in reality, I could saw off the LARGE end of my VHF-UHF antenna
and just use the end with the small beams..... Right?
(Not that I intend to do this, just asking).
In theory, yes. In practice, probably not. In most cases, those
combination antennas have been carefully tuned so that they perform well
across all the bands they pick up. Altering them in any way *WILL* alter
their capabilities. Every piece of metal within (depending on which
reference you want to believe) 1-4 wavelengths of any element has to be
accounted for in the tuning process. Depending on the exact design being
used (the "Yagi" is probably the most familiar), changing number of
pieces, size of any piece, or spatial relationship between any two
pieces even slightly can have anything from very little effect to an "I
can't freakin' believe it!" huge effect on the antenna's performance.
Lop a chunk off any of them, and it's pretty likely that they'll go
almost completely "out of tune" for whatever part you try to keep in
service. It wouldn't be impossible to retune an antenna once the VHF
section is chopped off, but chances are high that it would take so much
time/effort/tinkering to do it that it simply wouldn't be worth
bothering to make the attempt.
Or to put it another way, I could buy a UHF (only) antenna, and would
have a much smaller antenna on the roof. Right?
Yep.
I could see having a smaller antenna as a benefit, because I could
make my mast a few feet higher without having so much worry about high
winds ripping it down. Of course I am not sure if another 6 or 8 feet
of mast would make much difference.
In theory (once again...) raising an antenna any amount is helpful. But
in practice, there's a "minimum increase" number (Which I can't remember
for certain without looking it up - I'm wanting to say it's 10-12 feet)
below which the change doesn't give any significant payoff for the
effort.
And no, it doesn't matter that a station is now on a VHF channel, yet
transmitting digital - What's happening is that they're transmitting on
two separate frequencies - The standard analog signal on their "old" VHF
frequency, the digital signal on their "new" digital frequency. Which,
in *ALL* cases, is in the UHF band.
--
Don Bruder -
- If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info