[mythtv-users] Antenna wiring question

Barry Martin Barry_Martin_3 at Q.COM
Mon Nov 11 15:52:44 UTC 2013


Hi Craig!

>>>After my Comcast bill went up $29 in one month, 
>>>I decided to start exploring alternatives.
>>Don't blame you!  Did the same here.
>>I have an antenna in the storage area (attic for 
>>a story-and-a-half house) which goes to a 4-way 
>>splitter to feed the three tuners to my 
>>Mythbuntu Backend.  Use a 75? terminating 
>>resistor on the unused splitter terminal.  I 
>>also found I needed a pre-amp to boost the 
>>signal strength.  Because the antenna farm is 
>>only about 15 miles away I had to use a Winegard 
>>HDP269 to minimize pixellation when the wind 
>>blows and the signal strength suddenly 
>>increases/decreases.  (Too much signal will 
>>cause the AGC circuits to shut off.)
>You need a pre-amp at 15 miles?!?  What antenna 
>are you using; a rusty nail?  Perhaps the problem 
>is that the antenna is indoors?  In general, you 
>only get half the signal indoors compared to 
>outdoors.  However, a steel roof or stucco siding 
>can mean that only a tiny fraction of the signal 
>makes it through.  (Think Faraday cage!)  See 
>below regarding getting the signal from the 
>antenna to where you want to use it.

No, no rusty nail, though back in the ATSC days with the antenna farm being only a couple of miles from here that would have worked!  Found without the 10 dB pre-amp the signal levels were insufficient to drive the 4x splitter for the Mythbuntu Backend up here and the 8x splitter in the basement for the TVs.  There might be a 'dead zone' as where I pull up the driveway I do loose many of the semi-DX FM stations I listen to in the car.

As for Faraday Cage, used to live in one years ago with the aluminum siding.  Regular asphalt shingles, though the antenna is pointed through the gable.  At this point I'm pretty much stuck with using the indoor antenna due to the Other Half.  OTTOMH not sure which coax I'm using -- installed that years ago with a run along the sewer vent from the Storage Area (attic) to the basement.  Should be decent quality.




>>  The Mythbuntu Backend feeds the Mythbuntu Frontends via the Ethernet network.
>>I originally wanted to also use the one antenna 
>>to feed the various TVs for OTA.  Didn't quite 
>>work!  If the TVs had sufficient signal that 
>>overloaded the Mythbuntu Backend; proper signal 
>>levels to the Backend was insufficient for the 
>>TVs.  I tried various combinations of 
>>amplifiers, attenuators.  Ended up getting a 
>>second antenna to feed the TVs; that one also 
>>needed a pre-amp due to the 8-way splitter. 
>>(Not all TVs are on the Mythbuntu system.)
>I wonder if the real problem is/was wiring.  For 
>example, RG-59 has higher signal loss than RG-6 
>for a given run.  Lots of other little problems 
>can kill the signal on a branch.  

Agree.  There are actually two systems here: one antenna + amp + distribution for the Mythbuntu backend with four tuners and a second antenna + amp + distribution for the TVs.  

The 'Mythbuntu/Computer' system uses all new wiring, mainly because everything is on the same level (second floor).  The "TV" system does use some of the old/original distribution system such as the coax along the vent stack and distributions from the home run splitter.  TV tuner sensitivity does make a difference: the TV in the Family Room is 'touchy': it will drop out when others remain on.  Did try a temporary coax run to determine is the problem was with the original coax.  Same problem.



>Following link has some does and don't:
>http://www.familyhandyman.com/electrical/wiring/tips-for-coaxial-cable-wiring/view-all
>In the US, AntennaWeb is a pretty good resource 
>for determining the recommended antenna type, etc:
>http://www.antennaweb.org/

Yup: familiar with those.  Good reviews for the years I've been playing with electronics.  


>What I find funny is that homeowners in the 
>1960's knew all about this kind of stuff.  When I 
>was a kid, we had a big Yagi antenna on a 45' 
>tower next the house with a rotator.  Two of the 
>three channels we could get were at roughly 90 
>degrees to each other and both were 50+ miles 
>away.  Worked pretty darn reliably.

Yes, though was this for one TV?  Add the 7 dB loss from the 4x splitter (Mythbuntu system) or the 11 dB loss from the 8x splitter (TV system) and that of the coax itself and that's why it was necessary for me to add the 10 dB pre-amps here.

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