[mythtv-users] HDTV antenna quandry

[Daniel Kristjansson]

On Tue, 2007-04-24 at 22:40 -0400, Mark wrote:
> Hmm.  Did find some info on this on the net, seems like a black art.  

If you have antennas of different strengths and you are dealing
with longer wavelengths like VHF, then it is difficult. With UHF
this is much less of a problem because the distances involved
to simplify the problem are much smaller.

> Have you ever heard of
> channel specific yagi's combined on a single line to give each desired 
> channel?

Channel specific Yagi's are priced for the CATV market, so they
start at about $180. If that isn't a problem for you then this
is the best thing to get. Just make sure each antenna has the
same or similar gain in dB. If you are mechanically inclined
you can make your own channel specific antennas, I did this when
I first got started with MythTV and it worked well.

>   I know it'd be ugly,
> but with uhf yagi's being small, at least I wouldn't have 50 lbs on my 
> tower...  I used to have an old
> channel 32 yagi sitting around from the old ON-TV service from the 80's, 
> so I know they are available...

The cost of making channel specific antennas is not great.
But because they are marketed mostly to money-is-no-object
consumers (local cable monopolies), they are not cheap. A
channel specific Yagi is one of the simplest antennas you
can make, just google for the formula if you are interested
in making one. I've made these myself for 2.4 Ghz signals
UHF and VHF signals, and the weaker the tolerances for UHF/VHF
are easy enough that you will succeed on the first try if you
make one yourself. Studying up on making an antenna will also
help you understand how the antenna system will actually work,
all those antennas become one antenna when you combine them.
Also, if you make the antennas and one of your antennas has a
side-lobe where another antenna is pointing, you change that
antenna to move the side-lobe (but with channel specific yagis,
you probably don't need to do this unless the channels are
very close in frequency.)

-- Daniel