[mythtv-users] HDTV antenna quandry

[Brad Templeton]

On Tue, Apr 24, 2007 at 06:51:10PM -0700, Brad DerManouelian wrote:
> On Apr 24, 2007, at 6:40 PM, Mark wrote:
> 
> > Maybe one of you guys has run into this before...
> >
> > I'm planning on moving to HDHOMERUN boxes in the near future, but I  
> > have
> > a dilemma.  I have multiple stations nearby, Lansing 30 miles to  
> > the north,
> > Kalamazoo 45 miles west, and Detroit 60 miles East.  I need higher  
> > gain
> > antennas pointed in multiple directions.  I could do it with a rotor,
> > but then I might miss
> > a show on a channel where the antenna isn't pointed.  Best bet is
> > separate antennas.  Can antenna feeds for digital broadcasts be  
> > combined
> > with a splitter/combiner?
> > Or should I run each antenna feed to a separate hdhomerun and play  
> > with
> > channel/input  priorities until it works right? Currently this is my
> > only avenue for recording HD.
> > Cable and Sat don't carry what I want.
> >
> > Thoughts?
> 
> I use two antennae pointing in opposite directions going to a  
> combiner into my pcHDTV-5500 and can now get all the channels I want  
> in my area. This might be luck of the draw, though. Since you will  
> have two tuners, you might give this a shot by combining the signals,  
> then splitting again into each tuner to see if both tuners can get  
> all channels. If it doesn't work out, just get some channels on one,  
> the rest on the other and be thankful you have two tuners. :)
> 

My understanding is it's going to vary a lot based on your situation.
If you combine multiple antennas you will add to your multipath problems.
Digital TV won't ghost but you can get dropouts.

The ideal way to do this is to both tune your antennas for the channels
they are receiving, and to put filters on the lines notching out the
strong/ghosting channels they are _not_ receiving. 

Almost all digital TV is in UHF, but there are some exceptions (NBC
in SFBA is on channel 12, but you can receive that with a UHF antenna
decently well, so I have just a UHF antenna.)

Many antennas will also receive decently from behind them as well as
directly in front.

UHF signals are short, just 18 to 30 cm for a half-wave antenna.
Makes it harder to tune though.

As noted, one trick would be to try to find filters which block
out the channels you don't want from the antenna, but I don't know
where to buy those.   If you have a VHF digital station it should not
be too hard to find a filter to block either the UHF or VHF, and in
general you should not get too much interference there anyway as you
typically have 2 different antennas for that as it is.

Many antennas come with a large set of vanes of different lengths.  VHF
tend to come with one vane for each channel, I think you can just
break off the vanes for the channels you don't want.    UHF not so
easy.