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Old 13-Jan-2015, 2:41 PM   #1
rmurwin
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Help with setup in Spring Hill, FL

http://www.tvfool.com/?option=com_wr...2c15ced7ec6678

Spring Hill, FL 34608

Hey guys,

Thanks for your help in advance...

I'm trying to sort out a setup that will allow me to receive all of my local channels; in my scenario that would be all of the channels in the "green" and "yellow" located at 155 to 157 degree azimuth range. Since all of the channels that I want to receive are in the same relative direction, I don't think that I'll need to have any exotic antenna configurations, but I'm not positive... It looks like the lowest NM that I'm dealing with is going to be in the 25 range, so I don't think that is going to be an issue either... So as far as selecting an antenna goes, I don't think I've got any difficult requirements, but I'm still unsure of what my best choice would be. Where my situation may become more complicated is that I'm going to be connecting to at least 4 televisions, with the addition of a couple computer based tuner cards for DVR functions a real possibility... I'd like to mount this antenna on a mast at the 25 to 30 ft range, so I need some advice there as well...

To summarize:
1) Which antenna is the best choice for my location?
2) What are the requirements to feed the signal to up to 6 tuners?
3) Which mast is the best choice for mounting the antenna at 25 to 30 feet in the air?

Thanks for any help or advice,
Richard
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Old 13-Jan-2015, 3:29 PM   #2
timgr
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Hi Richard -

You have both UHF and VHF-high stations to receive, so your antenna will need to cover both of those bands.

Couple of routes you could go - first, use a modest antenna like the RCA ANT751 and then amplify it if your splitters give you too weak a signal. Ideally you'd put a medium-gain amplifier on the mast, before cable losses, so that the signal is strong enough to be divided as many times as is needed.

Alternately, you could go for more antenna gain and not have to amplify the divided signal. Something like the Antennacraft HBU33 or HBU44 http://www.antennacraft.net/Antennas/AntennasHBU.html may be sufficient. Channelmaster and Winegard offer similar antennas ... just compare the specs. Or you could go bigger and put a UHF-only Antennas Direct DB4e and an Antennacraft Y5713 on the same mast and combine them with an inexpensive UVSJ combiner. http://www.solidsignal.com/pview.asp?p=uvsj

Note that your splitters are simply voltage dividers - each divide-by-2 branch means a loss of power by 3dB. But the splitter does not add much noise, so the quality of the divided signal does not change much. You need enough amplitude at so that the resulting signal is not so weak that the tuners cannot lock on and decode.

Regarding a mast, there are lots of ways to erect a mast. The top rail from a chain link fence makes a good mast, at 10.5' long and around $10 from the home center. Usually you would exploit the configuration of your roof and building to erect the mast using one of several styles of brackets. Look here http://www.antennapartsoutlet.com/ for various methods like telescoping masts, tripods, eave brackets, etc.

Last edited by timgr; 13-Jan-2015 at 9:23 PM.
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Old 13-Jan-2015, 5:13 PM   #3
ADTech
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Quote:
Note that your splitters are simply voltage dividers
Technically, they're power dividers.
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Old 14-Jan-2015, 2:14 PM   #4
rmurwin
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Thanks for the response and the good information!

It looks like my choices for an antenna locally are either the HBU55 or the HBU33; is it better to go bigger?

The HBU55 has a gain of about 9; that would mean that I'm looking at a margin of around 34 to 35 for my lowest signal? Do you think that's enough to go with an 8 way splitter like this one without the need of an amplifier?

My house has a hip roof on all sides, so I don't have a high eave to attach the mast to, but I was thinking of going with a telescoping mast longer than I need so I can keep each section from being fully extended. I would drill new holes and put bolts through to mount in the new, shorter location. Does it sound like I could do that with a concrete pad ground mount and a bracket to the fascia and not have to use any guy wires?

Thanks again,
Richard
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Old 14-Jan-2015, 2:41 PM   #5
rickbb
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For how high you can go without guy wires you're best bet would be to ask the mast manufacture.

If you're building your own, there is some complicated math involved. Wind load deflection of the antenna X max wind speed X height of mast X type of mast material X thickness of mast material X, well you get the picture. It's all well above my last math class.


An 8 way splitter means 35db / 8 = 4db. Plus some more loss since the splitter is not 100% efficient. You may need an distribution amp instead of a plain splitter.
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Old 14-Jan-2015, 5:12 PM   #6
timgr
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Isn't 8 = 2^3 ... 3 * 3 dB = 9 dB down?

I would go bigger, if for nothing more than to make more of a statement with the antenna. Last I looked the HBU55 is $80 shipping included direct from Radio Shack. Realize it's big - a 12' boom.

You could put a 10' tripod straddling your roof ridge, and a short mast above that. Should not need any guy wires.
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Old 14-Jan-2015, 5:54 PM   #7
ADTech
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If you're working with voltages, a 50% reduction/gain is 6 dB, not 3 dB.

Quote:
An 8 way splitter means 35db / 8 = 4db.
Nope. It's closer to 3.5*3. Typical insertion loss is around 3.5 per split, I've tested anywhere from 3.2 to 4.4 dB insertion loss in 2 port splitters. An 8-port splitter usually has around 10.5 dB insertion loss. More or less, depending on the device's efficiency at the frequency tested or specified. If you use a nominal value of 3.5-4.0 dB per half split, you'll stay close enough to keep out of trouble.

If you allow for 11 dB for an 8 port splitter in your distribution link budget, you'll be okay.
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Last edited by ADTech; 14-Jan-2015 at 6:01 PM.
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Old 14-Jan-2015, 7:26 PM   #8
rickbb
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OK, no one will ever accuse me of being a math wiz as it's never been my strong suit. But;

If loss is 3.5 per split, why is it 3.5 x 3? Why not 3.5 x 8 = 28 db loss?

Why does an 8 way splitter only lose 10.5?
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Old 14-Jan-2015, 10:30 PM   #9
timgr
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Each split doubles the number of outputs. Split every branch into two for three times and you have eight outputs. Each output branches 3 times at ca 3.5 dB each to give 10.5 dB.
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Old 14-Jan-2015, 10:54 PM   #10
ADTech
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Short answer: Decibels add or subtract, not multiply or divide, when calculating gain and loss in a system.

Long answer:

Total insertion loss is calculated from the input to a single output and assumes that all outputs are equal unless otherwise specified.

Split once (two outputs), each is down about 3.5 dB from the input.

Split each of those outputs again, you have four outputs, each down about 7 dB from the original input.

Split each of those yet again, you now have eight outputs, each down about 10.5 dB from the original input signal power level.

Easy, eh?
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Last edited by ADTech; 14-Jan-2015 at 11:12 PM.
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Old 15-Jan-2015, 1:15 AM   #11
rickbb
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OK, makes sense now. It's like a 3 layer pyramid or branching tree.

1st split into 2 outputs,
2nd splits those into 2 each for four outputs,
3rd splits those 4 into 2 each for the final 8 outputs,
hence the 3 X 3.5 loss.
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Old 15-Jan-2015, 2:25 AM   #12
ADTech
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You got it!
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Old 15-Jan-2015, 7:33 PM   #13
rmurwin
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So, I'm good with the 8 way without an amplifier then?
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Old 17-Jan-2015, 10:15 AM   #14
timgr
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Quote:
Originally Posted by rmurwin View Post
So, I'm good with the 8 way without an amplifier then?
Should be fine, as long as there are no other problems with the antenna placement. Realize that your plot is a simulation that does not account for local-scale features, like trees and buildings, and you could have unexpected local EM interference of some kind.

You have any antenna now? If I weren't willing to just go to the final setup, I'd get some cheap antenna like rabbit ears and try it out on the roof where you plan to put the big antenna.
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