[mythtv-users] HDHomerun signal strength required

[Brian Wood]

backuppc at sundquist.imapmail.org wrote:

> Right now, I've got two of these:
> 
> http://www.radioshack.com/product/index.jsp?productId=2103088&cp=2032057.2032187.2032189.2032205
> 
> I got those over the channelmasters because (a) could buy local and (b)
> the hdtvprimer pages indicated the channelmasters weren't too
> directional, so that I would have more of the possible interference
> problems.  I was under the impression that pointing two boom antennas
> in opposite directions would not lead to interferences, but I guess I
> was wrong.

If they are receiving the same channel then the signals from the two of 
them may well be out of phase, resulting in cancellation and/or reflections.

No typical VHF TV antenna is terribly directional, especially with 
strong local channels. Parabolic UHF antennas are more directional, but 
even a solid reflector dish has significant off-axis lobes.

> 
> My wife would probably kill me if I started going out buying more
> antennas at this point (although the 4221 and 4228 aren't too bad), so I
> would like to experiment more with the two U-75R's that I have now.
> 
> My house is ranch which means the attic is quite long.  If I separate
> the two laterally, will that help?  As you point out above, it doesn't
> make sense to try to calibrate the phasing since I am looking at
> channels ranging from 14 to 43.  Practically speaking, the maximum
> lateral spacing I could achieve would be on the order of 30 to 40 feet
> or so.  I'm not sure that would be enough to make it worth the effort.
> What do you think?  It also would put me closer to big evergreen trees
> at either end of the house.
> 
> I had previously discounted use of a preamp precisely for the issue you
> raise, that some of the channels are quite strong while others are
> quite weak.
> 
> I guess I'll be crawling around in my attic with my wireless laptop
> ssh-ed into my mythtv box checking signals and see what I can get just
> rotating the two antennae currently on the same mast.  If nothing
> works reliably, I may have to break down and try Craig's suggesion and
> put a 4221 or 4228 on the roof this summer and see if the back-side
> approach works.

Unfortunately the best answer is sometimes the pragmatic approach, just 
try different setups and see what works. Most antennas are mounted close 
enough to the ground and other objects that the theoretical patterns are 
just that: theoretical.

beww