[mythtv-users] Antenna advise

[Barry Martin]

Hi David!

<Quote>
I just got my notice that comcast will be encrypting my basic channels. I'm
looking to get setup with OTA channels. I played around with a local
station and a "paperclip" antenna and things seem to be working well. I
need advise on a proper antenna and I know there are several variables to
consider. I have researched these two sites:
http://antennaweb.org
http://www.tvfool.com
I have gotten alot of useful info but I really need to find out which will
be the best antenna since a lot of effort goes into getting the unit,
setup, etc... and I don't want to return one if possible.

This is the info per tvfool:
channel NM   Power Path    Miles  Azimuth  VHF UHF
43        64.2   -26.6   LOS    3.5     91 95                X
19        42.1   -48.7   LOS    27.3   112 117            X
8          37.6   -53.3   1Edge 25.6   19 23        X
49        21.9   -69      2Edge 46.1   4  8                   X
51        21.6   -69.2   2Edge 46.1   4  8                   X
11        21.4   -69.5   2Edge 46.6   4  8           X
26        21.3   -69.5   2Edge 47.5   5  9                   X
47        19.5   -71.3   2Edge 47.5   5  9                   X

It seems that a two antenna setup should work:

antenna 1 (UHF) Indoor Multi-Directional
channels 19 and 43

antenna 2 (VHF & UHF) Rooftop Large Directional
channels 8,11,26,47,49,51

Please let me know your thoughts.<end quote>

All my local stations are really local, so I have the opposite scenario, but will make a few suggestions based one the 'fun' I've had here with my system.

First question, how many tuner inputs does your Mythbuntu Backend have?  I've seen three, four and eight in various messages.  Some cards have multiple tuners but only one input, so just need to count the inputs.  One tuner is needed for each recording session.  If you want to record two shows at the same time you will need two tuners.  Some cards have two tuners, so one input.

Each input requires a connection to the antenna, so a splitter will probably be required.  Splitters will reduced the signal level to the tuner, so if possible use the proper splitter -- don't use an 8-way splitter with four tuner inputs, for example.
Device                                 dB Loss

Splitter, 2x                             - 3.5 dB

Splitter, 4x                             - 7 dB

Splitter, 8x                             -11 dB

Coax, RG-6/U QS, 100'         - 5 dB

Coax, RG-59/U, 100'             - 7 dB


So, because of the loss you may/will probably need to boost the signal level again.  I would probably go with a mast-mounted pre-amplifier.  This will amplify the signal at the source (at the antenna) rather than where the splitter is.  Benefit: the mast-mount location  won't also amplify spurious signals picked up by the lead-in coax.



Most of your stations are distant (46 and 47 miles), two mid-range (25 and 27 miles), one almost on top of you (3.5 miles.)  Even more 'fun' is one each of the midrange and distant transmitters are VHF.  I'm guessing you are correct with the two-antenna system, but more because of directionality vs. distance.  My guess is one antenna pointing to the 19, 4.8 and 5.8° stations and the other towards the 91 and 112° stations.  What I would try is one antenna, pointing towards the 91 and 112° (so 100° to split the difference) and see if it will also receive your other stations.  The "100°" stations are distant, the others are local and mid-range, so maybe will also sufficiently be able to pick these up "on the side".  Otherwise I'd probably go with the two antenna scenario, and I'm thinking rather than use a combiner (generally sold as a splitter/combiner) and its 3 to 4 dB loss consider have one or two tuners on this antenna and the other tuners on the other.

Yes, a lot of playing around -- it is not an exact science.



BTW, if you need to amplify the very local (3.5 mile) station I would consider using a Winegard HDP269.  This pre-amp is designed to not cut-off when a very strong signal is received.  (And yes, a too-weak signal will cause the blue screen as well as a too-strong signal.)



Good luck!

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