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Old 5-Aug-2010, 8:30 PM   #1
nsjames
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deep fringe ashland OH

So, I've been looking at the plots and RF guides.

I'm located in 44805, exactly between the transmitters of Cleveland and Columbus OH.

I decided that I'd rather shoot for Columbus, since I don't like cleveland sports, and the CLE FOX channel is VHF.

So I've picked up a 91XG antenna for UHF. It will be mounted on the top of my house, approx 35 feet up. My house is on a ridge and is higher than the immediate surroundings. If needed I could get another 10 feet of height, but I would have to make a mast and tripod for the roof.
I'll be using a mast mounted motorola preamp that I've got laying about. 15 DB

Gain from the antenna averages about 14 DB
with the preamp I'm at a total of about 27 DB of gain. I'll be pushing this through about 70 feet of RG6 to a single HDTV, no splitters or splices, save for the power injector for the pre amp.

NM for the Columbus stations with my antenna mounted on the roof is looking to be between 12 and 19.

Is this feasible? I get better NM from the Cleveland channels, but I would prefer the Columbus stations.

I also will assume that with my cable length and weak station signal that I will not run into any signal overload issues at the tuner. WHat's the strongest preamp I should consider if I get signal but it is dodgy? I will buy another preamp if I must, but trying to do this on the cheap with random stuff in my basement. I've read nothing but stellar reviews about the CM 7777 preamp for the deep fringe areas.

Last edited by nsjames; 5-Aug-2010 at 8:32 PM.
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Old 5-Aug-2010, 8:36 PM   #2
nsjames
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forgot my TVFool chart

http://www.tvfool.com/?option=com_wr...9fbe9822a4a30e

stations I care about are from the two antenna locations @ 220 and 218 mag az. so a 15* beam width from the 91xg should get those 4 stations without a rotator correct?
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Old 5-Aug-2010, 11:29 PM   #3
ADTech
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Like living on the edge, eh?

I doubt you will get all four Columbus stations reliably most of the time. I would be pleasantly surprised if you did. I'd suspect okay reception during favorable conditions, but none as soon as the propagation conditions wane.

The beam-width is fine but the forecasted signal powers are pretty marginal.

Preamplifier gain does not add to your noise margin, only the antenna's net gain does that. Instead, the amplifier's noise figure must be subtracted from your calculated NM. If you don't know the Moto's NF, I'd recommend using a pre-amp of known performance such as our PA-18 which I've measured to be between 1.8 and 2.2 dB (frequency dependent) on our 8970A NF meter.

Additionally, all those channels have co-channel interference warnings. You might find that what little desired signal makes it to the antenna gets clobbered by interference.

Good luck and let us know your results.

Antennas Direct Tech Support.

Last edited by ADTech; 5-Aug-2010 at 11:41 PM.
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Old 5-Aug-2010, 11:43 PM   #4
Dave Loudin
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You can't add the amp gain to the antenna gain to determine your overall NM. It amplifies the noise as well as the signal that the antenna picked up. What you're doing is zeroing out the cable loss. So, you add the antenna gain and subtract the amp's noise figure from the NM in the table to see what you have at your receiver.

I think you'll be disappointed in your Columbus reception results. You've got 2-edge and tropo paths, which are notoriously unstable. You'll need at least +15 NM for reliable reception, and I don't see that happening. You will be able to get the Cleveland UHF stations just fine, though. However, for Fox and CBS, you will need to add a VHF antenna.

Good luck!
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Old 6-Aug-2010, 1:44 AM   #5
No static at all
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nsjames,

If I were in your shoes, I would at least try Columbus reception just to see what you get. I agree with the others here that it looks bleak, but sometimes you just get lucky & may get a few of the stations with enough reliability for regular viewing.

I put up a 91XG with similar signal strengths/distance & was pleasantly surprised at the results. With noise margins below -13, 5 stations have decent reliability & 3 more are watchable 50% or more of the time. We ended up using the Winegard 4800 UHF only preamp. It worked noticeably better than the CM7777.

Good luck!!
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Old 6-Aug-2010, 2:39 AM   #6
Billiam
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Originally Posted by No static at all View Post
nsjames,

If I were in your shoes, I would at least try Columbus reception just to see what you get. I agree with the others here that it looks bleak, but sometimes you just get lucky & may get a few of the stations with enough reliability for regular viewing.

I put up a 91XG with similar signal strengths/distance & was pleasantly surprised at the results. With noise margins below -13, 5 stations have decent reliability & 3 more are watchable 50% or more of the time. We ended up using the Winegard 4800 UHF only preamp. It worked noticeably better than the CM7777.

Good luck!!
Second that on the 91XG. I am getting rock solid reception on Channel 15 which is 75 miles away over hilly terrain despite the fact the NM is at about 9.6. The signal strength reads consistently around 70% or even a little higher on this channel!

NoStaticAtAll. How much better is the 4800 pre amp when compared to the 7777? Did you see across the board improvement in signal strength on every channel? Or were you able to pick up more stations with the 4800 than you have with the 7777?
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Old 6-Aug-2010, 6:13 AM   #7
John Candle
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Reception

Might try http://www.researchcomms.com/hdtv.html , to squeeze out that last bit of noise margin in your favor
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Old 6-Aug-2010, 12:24 PM   #8
No static at all
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Originally Posted by Billiam View Post
How much better is the 4800 pre amp when compared to the 7777? Did you see across the board improvement in signal strength on every channel? Or were you able to pick up more stations with the 4800 than you have with the 7777?
No new stations, but the 4800 helped to reduce dropouts with stations right on the digital cliff.
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Old 6-Aug-2010, 1:11 PM   #9
Dave Loudin
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Originally Posted by Billiam View Post
Second that on the 91XG. I am getting rock solid reception on Channel 15 which is 75 miles away over hilly terrain despite the fact the NM is at about 9.6. The signal strength reads consistently around 70% or even a little higher on this channel!
Every path is different, which is why checking the path profile (by clicking on a station's listing in TVFool) is pretty handy. In his case, the ridges seem to be right at the path midpoint, which puts him beyond the radio horizon for Columbus. He has to rely on the generosity of Mother Nature to bend signals over. The modelling of the path for signal strength at broadcast reliability indicates no reception.

Is your NM + or - 9.6? Is this with antenna gain/preamp noise figure or without?
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Old 6-Aug-2010, 1:24 PM   #10
Billiam
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Originally Posted by Dave Loudin View Post
Every path is different, which is why checking the path profile (by clicking on a station's listing in TVFool) is pretty handy. In his case, the ridges seem to be right at the path midpoint, which puts him beyond the radio horizon for Columbus. He has to rely on the generosity of Mother Nature to bend signals over. The modelling of the path for signal strength at broadcast reliability indicates no reception.

Is your NM + or - 9.6? Is this with antenna gain/preamp noise figure or without?
2 edge plus 9.6. So it is in the red.

After viewing his TV Fool report the odds of obtaining reliable reception of any of the Columbus stations is slim. Occasionally there are exceptions to the rule though. I have a friend north of Minneapolis, MN that is getting reliable reception of a Wisconsin station that is 2 edge and showing a minus 8 or so NM.
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Old 6-Aug-2010, 3:20 PM   #11
nsjames
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Originally Posted by ADTech View Post
Like living on the edge, eh?
Yeah I do, I like playing with dangerous toys too.
Nice to see that Antennas Direct has a rep on here though.
My antenna arrived today, I was amazed that the box was so small. Packing isn't great inside, but I suppose that it is just a bunch of metal parts. It appears undamaged despite the abuse FedEx gave the box.
Quote:
Originally Posted by Dave Loudin View Post
You can't add the amp gain to the antenna gain to determine your overall NM.

You will be able to get the Cleveland UHF stations just fine, though. However, for Fox and CBS, you will need to add a VHF antenna.

Good luck!
Yeah I don't know what I was thinking when I was adding up the gain. I guess I didn't equate the NM to a SNR number.

I'm positive I can get the Cleveland stations, I just don't want them.

I will point it at columbus and see what happens. If I can't get them reliable I will go after the cleveland stations and add a VHF antenna and combiner. I may pick up a rotator later down the line so I can get the Columbus statons on good days, and swing it over to the Cleveland stations on the bad.

Another quick question, what kind of signal meters will work for the HDTV bands? I've got a basic satellite signal meter from when I was doing Direcway installs, it's self powered, so I may give that a whirl.

Last edited by nsjames; 6-Aug-2010 at 3:23 PM.
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Old 6-Aug-2010, 5:45 PM   #12
Tower Guy
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Originally Posted by nsjames View Post
Another quick question, what kind of signal meters will work for the HDTV bands? I've got a basic satellite signal meter from when I was doing Direcway installs, it's self powered, so I may give that a whirl.
In addition to the meter in your TV set, you can find these on ebay:

http://www.sadelco.com/default.asp?p...&nproductid=56

Right now they're listed at $495. I got mine for $295, but then had to buy a new battery charger from Sadelco.
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Old 6-Aug-2010, 6:58 PM   #13
nsjames
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those are a bit out of my budget for something I'm likely to use once.

I'll hook the accutrac up to it, but it's likely not going to work.

I'l just use the signal meter built into the set. Hopefully it doesn't suck.
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Old 7-Aug-2010, 11:00 PM   #14
nsjames
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well, it didn't work out like I had hoped. I was able to get about a 30% raw signal strength, but could never get anything more than 8% on the error correction signal quality meter.

I swung it to Cleveland and got 100% on the UHF signals. I even managed to pickup WMFD, the local mansfield channel in the opposite direction, and the Akron PBS channels. I'll pick up a VHF panel and a combiner to round out my Cleveland channel lineup. Sucks, but I guess that's what the terrain dealt me.

I may try to make a VHF panel, it doesn't look that dificult. Otherwise someone recommend me a cheap VHF only antenna.

Last edited by nsjames; 7-Aug-2010 at 11:02 PM.
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Old 8-Aug-2010, 3:51 AM   #15
Tower Guy
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Originally Posted by nsjames View Post
Otherwise someone recommend me a cheap VHF only antenna.
Y5-7-13

http://www.solidsignal.com/pview.asp...u=716079000987
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