Amplifying OTA signal...

[beelzerob]

Being in the boonies, I've been starving for HD sunday football games since all of the dish and cable companies are bastards who don't include the OTA HD feeds in their services.

So, I went to radio shack and bought a 30db signal amplifier and a 160" OTA antenna. An initial test showed that it was adequate enough....only a few dropouts on the CBS channel, and I get fox, although the game wasn't in HD.

I'm going to put this in the attic, since that will put it up even higher, and keep it safe from weather and lightning, and whenever I can put anything INSIDE the house, I'd rather do that.

The signal amplifier I got has 2 boxes, which I don't really understand...but they seem to work. The first box has "from antenna" as an input and "to power" as an output. That box has no power connections of any kind. The second box has "from amp" as an input, and "to TV" as an output. That box is the one with the power cord and the gain rheostat. So it seems that the first box, without the power supply, is actually the amp.

Anyway....what I'm wondering is how important it would be to put both of those pieces up in the attic with the antenna. I know the general idea is to amplify the signal close to the source, so that you aren't picking up any interference between the antenna and the amp and amplifying those. I'd rather put the plugged-in thing down in the basement than wiring an outlet in the attic and leaving it up there plugged in and unattended.

The distance from the antenna down to the wiring room is probably about 60 - 80 ft. And of course, I'm using RG6QS the whole way.

Do you think it'd matter to the signal quality if I put one or both of those boxes down in the basement instead of up in the attic near the antenna?

 

[brotsten]

The first box is probably powered via the coax cable from the other unit.

I wouldn't think a 60' to 80' run would need any amplification. You probably need a higher gain antenna, or maybe some aiming. Higher is usually better also.

I saw significant differences in tuners also, what are you using?

Brian

 

[jwilson56]

Well from person experience I would not put the antenna in the attic. You will cut the digital signal down (in the winter even more with the snow on the roof).

OTA is one of those its there or its not. You do not want anything in the path that you can avoid.

 

[BrettS]

Do you think it'd matter to the signal quality if I put one or both of those boxes down in the basement instead of up in the attic near the antenna?

As you guessed, the device without the power cord is the actual amp and the device with the power cord is the power supply. It actually sends the power down the cable to the amp. The amp (no power cord) should be installed as close to the antenna as possible, so that should definitely go in the attic. The power supply can be installed pretty much anywhere down the line (which is why they made it two devices... so the amp can go by the antenna and the power supply can be installed near an outlet).

HTH,
Brett

 

[beelzerob]

Well from person experience I would not put the antenna in the attic. You will cut the digital signal down (in the winter even more with the snow on the roof).

OTA is one of those its there or its not. You do not want anything in the path that you can avoid.

Hmmmm....I didn't think about snow. :blink: When I lived in Hell before, we had our OTA antenna in our "attic" (really just a crawlspace almost), and that was under clay tiles for shingles, and it got great reception still. Would snow on thin asphalt shingles really be any worse? We get snow, but not typically a LOT of snow. When I tested this antenna last weekend, it was sitting on top of a ladder inside the house...so even going through the wall and insulation, it was doing good. Overall, of course, I agree....for OTA, every little bit helps...but I really hate the idea of this huge antenna being outside, for many reasons beyond just the aesthetics.

I should clarify the distances here, too....

Currently the RG6 going up to the attic goes down to our wiring room first in the basement...that's about 80 ft distance. Then from there, it goes another 80 ft to the great room, where it would plug into the TV for tuning.

The amplifying I'm talking about is not so much for the wiring distance, but just to increase the gain on the antenna signal. Without the amp on, and even with this 160" antenna, I don't get any signal.

 

[beelzerob]

As you guessed, the device without the power cord is the actual amp and the device with the power cord is the power supply. It actually sends the power down the cable to the amp. The amp (no power cord) should be installed as close to the antenna as possible, so that should definitely go in the attic. The power supply can be installed pretty much anywhere down the line (which is why they made it two devices... so the amp can go by the antenna and the power supply can be installed near an outlet).

HTH,
Brett

Ok, that's good clarification. That explains why the non-powered box has an indention for being mounted to a mast. I'll put it right next to the antenna.

 

[Steve]

You simply need to just do what works for you. Every situation is different and depends on the atmosphere, path and obstructions between your antenna and transmitter, multipath interference, type of construction, etc, etc. I am about 65 miles from most transmitters and have a VU-90 antenna in the attic under concrete tiles and it works fine. The only bad part is sometimes it can be a pain to test it in the area you need/want it.

 

[Photon]

The reason the amp should go as near as possible to the antenna is so it amplifies just the signal. The lead-in, even coax, will pick up some noise and you don't want to amplify that. Put the amp at the antenna and you maximize signal to noise ratio.

I bought a five-element VHF antenna from Radio Shack in 1976, and it traveled with me for my USAF career. It is now in my garage attic where I have to be careful how I point it or I pick up channel 4 from Michigan, I think Grand Rapids, when I really want the Milwaukee station. Grand Rapids is about 125 miles as the crow flies; WTMJ's tower in Milwaukee is maybe 25 miles.

 

[amirm]

The amplifying I'm talking about is not so much for the wiring distance, but just to increase the gain on the antenna signal. Without the amp on, and even with this 160" antenna, I don't get any signal.

In general, amplifiers should be used to eliminate the effect of the cable. Using them otherwise is liable to overload the input on your receiver and at any rate, they add a lot of noise. So the best place definitly is on the mast near the antenna. The most authoritative web site on HDTV reception is at hdtvprimer.com. The section on antenna basis is specially useful in this context: http://www.hdtvprimer.com/ANTENNAS/basics.html

"Many people think that connecting an external amplifier to the antenna will improve the performance of the antenna. This is usually wrong. Receivers always have more gain than is necessary. (The receiver has an Automatic Gain Control circuit, AGC, which will reduce strong signals. The AGC makes all stations the same strength at the demodulator. When you add a preamplifier, the TV receiver lowers its own gain, usually by an equivalent amount.)



Normally the signal to noise ratio will be set by the receiver’s first transistor. But if an external amplifier is added, the first transistor in that amplifier determines the S/N ratio. (Since the external amp will greatly magnify its own noise as well as the signal, the receiver’s noise becomes insignificant.) Since there is no reason to think the external amp’s first transistor is quieter than the receiver’s first transistor, there is generally no benefit to the S/N ratio from an external amplifier.



But an external amplifier will compensate for signal loss in the cable if the amplifier is mounted at the antenna. Without this amplifier, a weak signal, just above the noise level at the antenna, could sink below the noise level due to loss in the cable, and be useless at the receiver.



RG-6 will lose 1 dB of the signal every 18 feet at channel 52. For a DTV channel, 1 dB can be the difference between dropouts every 15 minutes (probably acceptable) and every 30 seconds (unwatchable). This author recommends a mast-mounted amplifier whenever the cable length exceeds 20 feet. (If you are in a good-signal area or you have no high-numbered UHF channels, you can to an extent ignore this advice.)"

Please follow the link for more info.

I should note however that in practice, these amps do tend to make the reception better even at the end of the line as you noted. But is best to use them as intended per above. Also, radio shack amps are not very good. Read the web site for lower noise products which work better.

And be sure to check out the graph here, on the performance of various antennas: http://www.hdtvprimer.com/ANTENNAS/comparing.html

 

[beelzerob]

Damn...I was afraid that would happen. I'd go buy a huge expensive antenna only to find there's something better out there online....

*sigh*

Good thing I kept all the packaging and radio shack takes returns.

Well, the winegard PR-8800 looks good, and it's half the price of the one I bought. Being smaller in size, it would make it alot easier to mount in the attic.

 

[electriclight]

beelzerob, do you have any VHF stations (chan 2-12) that you want to receive? The PR-8800 is UHF only where as the 160" RS that you have is a VHF/UHF hybrid. So, you might just want that 160" giant.

 

[amirm]

Another wonderful tool is located here: http://www.tvfool.com/index.php?option=com...r&Itemid=29

Put in your address and it gives you a table and graph of the stations and how strong they are. Further, you can select the button for post Feb 2009 when some of the stations return their UHF spectrum and go back to VHF. To the extent you don't care about the few that will do that, then a UHF-only antenna would do.

Also, some UHF antennas have reasonable reception for high VHF channels (e.g. db-8 styles). You can see this in the graphs at the link I provided earlier.

The tvfool output also shows you the direction you need to aim your antenna (note the bit about magnetic vs true north).

 

[mdesmarais]

beelzerob, do you have any VHF stations (chan 2-12) that you want to receive? The PR-8800 is UHF only where as the 160" RS that you have is a VHF/UHF hybrid. So, you might just want that 160" giant.

I was going to ask this question too. In my area, it is all UHF. I have a big square antenna, flat as a board. I use this site-

http://www.antennaweb.org/aw/welcome.aspx

to determine size and point, and stations available. As far as I know, it is the authority. I ended up with a large directional, but did not need the advised pre-amp. Mine is mounted on the roof.

 

[beelzerob]

I was going to ask this question too. In my area, it is all UHF. I have a big square antenna, flat as a board. I use this site-

http://www.antennaweb.org/aw/welcome.aspx

to determine size and point, and stations available. As far as I know, it is the authority. I ended up with a large directional, but did not need the advised pre-amp. Mine is mounted on the roof.

I've been to antennaweb quite a few times to get to this point. It helps knowing which way to point the thing. However, even antennaweb doesn't list all the channels I'm seeing. It says CBS is channel 10 and not digital, but I was watching HD Football on CBS 10.1 this last weekend.

I have no idea if I need VHF...I only care about HD channels, so if VHF won't be used for HD channels, then no worries. The antennaweb site doesn't list any digital channels as using VHF, but like I said, it doesn't list all the channels I know exist.

I'll check out that other site listed (tvfool) tonight and see what it says.

Thanks for all the help, guys! I hate stuff like this.....where it's never ever as easy as "well, what's the best one??".

 

[beelzerob]

Well, tvfool at least lists the 10.1 CBS channel. But I can't tell from that if any of them are VHF vs. UHF.

Geez...I'm not sure I want to go through the hassle of returning this big-ass antenna if I can't be fairly certain the new one I get will be BETTER. The charts on the hdtvprimer site are kinda helpful.

*grumble*