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afterdawn.com > forums > archived forums > hdtv discussion > help splitting my antenna signal
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help splitting my antenna signal
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smacko
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_ 		25. April 2010 @ 00:01 _ Link to this message    Send private message to this user   
i have to split the orignal antenna with an old splitter then run a very thin coaxe cable to another old splitter then a decent size cable to the tv, an thoughts on the right thing i need to get my signal to come in. I know i can get rid of the smal white cable but what are the best signal splitters out there
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Paula_X
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_ 		25. April 2010 @ 00:26 _ Link to this message    Send private message to this user   
buy a distribution amplifier and use the best quality cable you can.. any passive splitters will cause over 50% attenuation of signal at each outlet.. more than 50% because of impedance matching. Try to keep cable lengths exactly the same on each outlet as well to minimise transmission effects like standing waves and out of phase end reflections. Ensure the cable runs are not any mulitple of signal wavelengths in the passband you need (very complicated in these digital days when co-channel and swr artifacts are not visible)..

http://www.dxing.info/equipment/rolling_your_own_bryant.dx

change parts to suit your chosen frequency band and in/out impedances (tables are available for most standard frequencies.. fyi.. 1/4 wavelength at 600MHz is like 4 inches!! and look at making an impedance matching balun for your antenna if it doesn't have one already. (standard UHF antennas are 300 ohm balanced feed at the screws.. feeder coax is 75 ohm same as the termination impedance of the receiver.. a simple balun which can be "peaked" is between 3-5 inches and only a bit of coax) At the most simple a nice pair of 400 ohm resistors in series with each feed will usually make a small improvement.. adding 75 ohm parallel resistors downstream between those and the receivers will make sure they "see" something like the right impedance. (everything will be "apparently" in parallel as seen by the antenna so 400 may seem an odd choice at first glance.. 2x400 parallel = 200 in total/75 termination halved (32 ish)..70 ohms or so.. not too bad really.. better than the 32 that comes from just twisting the wires together.. then transmission line effects will be paramount rather than drastic impedance mismatch attenuation. For those you will need to know the exact transmission speed of the specific cables you use.. should be listed in the specs for any rf cables, but not in a form that the lay person can understand, let alone use.. rule of thumb above.. 600MHz = 3.5-4 inches for most standard 75 ohm solid core coax feeder.

This is not an exact science.. well it is, but there are too many variables to be any more than general unless on site with a heap of very expensive test kit. Hope all that makes sense and helps... It's often easier and less painful to just fit another antenna lower down the mast.. a foot away at least unless you want to pair them in a low signal area.
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This message has been edited since posting. Last time this message was edited on 25. April 2010 @ 00:27
smacko
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_ 		25. April 2010 @ 14:06 _ Link to this message    Send private message to this user   
I bought a Motorola Signal Booster 484095-001-00 Bi-Directional RF Amplifier, for $33 and some better coaxial cable and i hope that will really do the trick, i am only able to get fox sd as of now and that still looked good .
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Paula_X
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_ 		25. April 2010 @ 17:01 _ Link to this message    Send private message to this user   
sounds good.. dunno what frequencies you are on over there.. should be a listing somewhere. For digital you need something like +16dB gain from the antenna.. wideband yagi perhaps? I have a pair of outdoor yagis stacked inside and they aren't that great for my needs.. but I can't get up on the roof.
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smacko
Member
_ 		25. April 2010 @ 22:24 _ Link to this message    Send private message to this user   
i took out the smaller white connector and splitter and now get in around 6 channels up from 1, i would expect this thing to work,
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Paula_X
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_ 		26. April 2010 @ 05:57 _ Link to this message    Send private message to this user   
It will.. but it all depends on the signal you are feeding it in the first place.. old saying when it comes to signals.. garbage in - garbage out .. look where other people have their antennas pointing.. you might need to add a balun.

http://members.fortunecity.com/xe1bef/vhf-uhf-antennas.htm

plenty of info there.. sounds to me like you could really do with a panoramic signal strength meter.. well expensive. I use a UHF tuner set up to sweep the whole band, and a detector and oscilloscope to "see" the levels on the various channels.. even so.. mux5 is hopeless here.. -52dB down due to being at 10kW instead of 100 .. below threshold. My next project is to peak my stacked yagis to favour that frequency..

I can't help any more without knowing what channels you expect where you live and what frequencies they are on.. analog or digital. If you are trying to use indoor rabbit ears or something it's pointless with digital.. a good antenna and distribution system are essential anywhere but right up next to the transmitter.

http://www.kyes.com/antenna/antennatypes/antennatypes.html
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This message has been edited since posting. Last time this message was edited on 26. April 2010 @ 06:08
smacko
Member
_ 		26. April 2010 @ 22:35 _ Link to this message    Send private message to this user   
thank you and good luck with your project when you do get to it, i think this will get delivered in tommorow or wendseday and i will update. hell maybe all i need to do is turn the antenna, but i'll try the amp first and then turn, but i was getting abc hd and about 6 or 7 more channels before i had to split the antenna
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smacko
Member
_ 		30. April 2010 @ 11:08 _ Link to this message    Send private message to this user   
wow that signal booster worked greater, i would recomend that to anyone. I know get 2,4,7,12,20,25,28,50,62, 66, and a couple of canadian channels in clear. That is up from 2, 7,20,28, and 62 and the canadian channels in alright. Now i can watch the Bills play football. Plus, i haven't even turned the antenna to see if that helps out at all.
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smacko
Member
_ 		30. April 2010 @ 11:08 _ Link to this message    Send private message to this user   
another thing do you know if it uses alot of power having that plugged in or not
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