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-   -   Chances of receiving RF15? (http://forum.tvfool.com/showthread.php?t=15293)

eggman531916 18-Feb-2015 8:50 PM

Chances of receiving RF15?
 
Hello everyone. My question is what are my chances of receiving RF channel 15? I'm working on building a DBGH to attempt this. I'm also using an Antennacraft 10G222 preamp, and the line is split to three TV sets. I'm not sure about the accuracy of the TV fool report, as I probably shouldn't be getting RF 34, but, there it is coming in pretty decently. Also, I would like to pull in RF 27 to the north, but was wondering if that would be a lost cause.
Tvfool report at 18ft. (where my vert. stacked 9.5x9 8bay is placed currently, but blocked in the direction of RF15 by buildings)
http://www.tvfool.com/?option=com_wr...2c1590068cf19b

Tvfool report at 40ft. (where the antenna will be placed in the spring)
http://www.tvfool.com/?option=com_wr...2c158c608f1451

Tower Guy 18-Feb-2015 9:07 PM

The links do not point to a valid radar report.

eggman531916 18-Feb-2015 9:22 PM

Sorry about that Tower Guy. Let me try that again.
Here's the first one at 18ft.
http://www.tvfool.com/?option=com_wr...cd3f7debb7a4de

And the second one at 40ft.
http://www.tvfool.com/?option=com_wr...cd3fe9a60251ab

Tower Guy 19-Feb-2015 1:39 PM

WPSU is running two transmitters on channel 15 simultaneously. When running such a distributed transmission system there are areas where the two signals interfere with each other. You are in one such location. For you, the two signals are 47 degrees apart.

For reliable reception of WPSU you will need an antenna that has at least 10 db gain at one or the other of the two signals and a rejection of the other signal of roughly 25 db. Two widely available high performance antennas are the 91XG and the DB8e, both of them have side lobes in the -10 db range at 47 degrees on channel 15. That won't work.

To get 25 db rejection at 47 degrees you'd need to stack two identical antennas at the critical distance to null the interfering channel 15. You can find that distance on the chart here http://www.hdtvprimer.com/antennas/ganging.html The first null occurs on two antennas 17.5 inches apart. The second null occurs with antennas 50" apart.

I would not stack a pair of DB8e antennas due to cost and windload considerations. A pair of 91XGs could be stacked 50" part. For a smaller, more reasonable antenna, a pair of 43XG antennas stacked 18" apart with the two reflectors touching would reject the second transmitter roughly the same amount as a pair of 91XG antennas.

The key to the installation is a rooftop installation with the fewest number of trees in the direction of the transmitter that you would like to pick up. The small difference in the two NM values for the two WPSU transmitters says that either one could be best for you.

eggman531916 20-Feb-2015 3:29 AM

One last question.
 
Thank you Tower Guy. To be honest, with the low NM values, I wasn't even sure if I could pick them up. I'm not sure how low these values go and have a reasonable shot at receiving signal. I get a snowy RF 29 analogue from State College with my current set up, and if I input 27 on the TV, it gives me the "Retrieving Data" message. I figure I may give it a shot once the weather clears up a bit. Anyways, I have one last question. My bedroom TV has a really horrible tuner in it. Granted, it's about 100' run off of a split line. Do you think it would be a good idea to put a small, inline amp on that line only to boost the signal? I have on set of channels (WJAC and its subchannels) that consistently drop on that TV only. Normally, I don't even consider amplifying an already amplified signal, but I keep reading about people who run signal through a series of amps on the forums and was wondering if that may be an option.

Tower Guy 20-Feb-2015 12:48 PM

To see if additional amplification would help, move the TV set to a location with a shorter coax run or temporarily bypass your splitter. If it improves, the line amp will help. If not, the tuner probably has less ability to deal with multi path and an amp won't fix that.

GroundUrMast 20-Feb-2015 5:55 PM

Agreeing with TG, An amplifier can not distinguish between desirable signal and noise or interference... It will amplify all the signals present at the input of the amp. Then, amplifiers will add a small amount of noise and distortion of their own. Amplifiers can not / do not 'pull' signal from the air, antenna or coax... They 'push' signal + noise + interference + distortion through the loss of cable and splitters on the output side of the amp. If you drive an amplifier with too strong a signal, the distortion problem becomes extreme, leaving you with less or even no reception.


Signal quality and signal strength are not the same thing. Reliable reception starts with the correct type of antenna, it's location and aim. If the antenna is not located where it can intercept a clean signal, it doesn't matter how much you amplify the low quality signal...

Consider, would polluted water be any more healthful to drink if you delivered it to the tap at a higher pressure?

eggman531916 20-Feb-2015 8:44 PM

Thank you Tower Guy and GroundUrMast. I may move the TV and give that a shot. The one thing I did do at its current location was to run the signal through an Analog-Digital box. When I did that, the signal was loud and clear with no drops. That's why I wondered about adding an in-line amp. I have to admit, I've been reading through the forums here and at digitalhome.ca over the last couple of months and have learned alot. Again, thank you all very much.

GroundUrMast 20-Feb-2015 8:58 PM

To be sure we understand, what was the make & model of the 'Analog-Digital box'?

eggman531916 21-Feb-2015 3:34 AM

My apologies. Digital to analog converter.... I had it backwards. It's a Magnavox Model No. TB110MW9. It's the only thing I own that has some sort of signal strength meter on it. When I hooked it up to the TV in question, it gave me the same signal strength on all channels as it did when I hooked it up to the (better?) TV (Viore) in the living room, which is directly underneath (almost identical in cable run length) the problem TV (RCA).


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