Extreme fringe reception -6 DB to -19 DB

bluenote · 5-Sep-2014, 12:40 AM

Hey guys

I have an attic mounted crap combo antenna and I get all the canadian stations that are available and the closer US stations. But I'm interested in getting seattle and other us stations that are ~ 110 miles away with 2edge interference. (And some others are tropo).

Can anyone recommend antenna(s) to do this? If I can't get a decent # the project probably isn't worth doing so I'm really hemming and hawing and wondering what will be possible.

I'm also a little confused about stacking. It seems like I should be able to add the gains of two identical antennas together, but I've read that the max increase would be another 3 DB for doubling the antenna. !!!

Anyways, please give me your best advice on how many of the grey US ONLY stations that I might be able to get. There's also a slight wrinkle in the channel distribution, with 2 being VHF-HI and the rest UHF.

Here's my tvfool, done at 40 feet which would be about 10 feet up off my roof.

http://www.tvfool.com/?option=com_wr...d243dfaa8edffe

Thanks for any suggestions!!

GroundUrMast · 5-Sep-2014, 1:17 AM

A doubling of power expressed in decibels is nominally 3 dB. If each antenna is identical and receiving identical amounts of signal power and in matched phase and you can combine the outputs of each without loss then the combined power of the two would be 3 dB greater than one antenna alone. In practice, that's a lot of 'ands' in a row... 2 to 2.5 dB net gain is considered a good result.

I can't see you achieving reliable reception from Seattle... there's the primary problem of extremely weak signals compounded by co-channel and/or adjacent channel interference in most cases. Then there are no doubt some FM signals that would be potential sources of harmonic interference.

You need to be able to add the noise margin of the signal in the air together with the net gain of the antenna minus any balun and cable losses ahead of any active device such as a preamp. (Amplifier gain does not add to the antenna gain, because it amplifies noise received by the antenna while adding some of it's own noise. If the antenna can't get the job done, an amp won't fix it.) If the number is positive, you are getting to a point that may produce reception. But the NM figure listed in your report does not account for the effects of co-channel, adjacent channel, FM or any other source of interference. Also, at that distance, atmospheric conditions are going to govern a great deal of the path. As a result you're going to see a wide range of path loss variation as the weather changes. Sometimes the atmospheric conditions will be in your favor... but at least as often, not. On any given day the real and predicted NM on such a path could differ by well more than 10 dB.

If you still want to try, I'd get a big 7-69 combo or a big UHF panel and H-VHF Yagi... A preamp that tolerates strong signals and an FMI filter.

Winegard HD7698P and Antennacraft HBU-55 are a couple of combos to look at.

The DB8E + Y10713 pair is a another off the shelf solution for entry level DX'ers.

Another option is to roll y'er own... The GH10N3 comes to mind... and then there is the stuff of legend, the Rhombic.

Tower Guy · 5-Sep-2014, 1:51 AM

The only commercially available antenna with sufficient gain is the Sitco MU-192-38. That antenna is essentially 16 yagis cut to channel 38. It would get ABC and CBS and perhaps NBC. Expect it to cost over a grand.

5-Sep-2014, 6:58 PM

+=>

Here is a way to do it to receive the long distance Tv stations that can not be received with a Tv antenna.

http://www.tablotv.com.

The Tablo receiver is installed at a location that is easier to receive the Tv stations , close to the transmitters in the USA.

The receiver is at a relatives house or friends house.

The Tablo Receiver Streams Over The Internet to your internet connection or portable internet device.

--------------------------------------------

For reception of the close easy to receive , Canada / USA , Tv stations , install and Test reception with a.

http://www.channelmasterstore.com.

CM3000HD antenna installed above the Peak of the Roof in such a manner that reception is not , obstructed , impeded , blocked , buy the , attic , roof , building , in all directions.

As with any omnidirectional antenna , omnidirectional antennas are not 100 precent omnidirectional and will most likely need to be rotated to find the spot of best reception.

---------------

http://www.saveandreplay.com.

http://www.trentondistributors.com.

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Do not hide the CM3000HD antenna , hiding Tv antennas is a good way to have less reception.

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A antenna system amplifier will most likely not be required.

bluenote · 7-Sep-2014, 8:22 PM

Hi Gents

Thanks for weighing in and the suggestions. @GroundUrMast that was a very complete rundown, thank you. I'm going to take some time and mull it over considering the possible borderline results.

Unfortunately I'm not very interested in some kind of remote-viewing setup, because a) bandwidth considerations both ways, and b) I already have an extremely integrated HTPC setup and using the Tablo or other similar standalone app would be a downgrade.

thanks for the info guys!

stvcmty · 8-Sep-2014, 6:17 PM

Quote:

Originally Posted by GroundUrMast

You need to be able to add the noise margin of the signal in the air together with the net gain of the antenna minus any balun and cable losses ahead of any active device such as a preamp. (Amplifier gain does not add to the antenna gain, because it amplifies noise received by the antenna while adding some of it's own noise. If the antenna can't get the job done, an amp won't fix it.) If the number is positive, you are getting to a point that may produce reception. But the NM figure listed in your report does not account for the effects of co-channel, adjacent channel, FM or any other source of interference. Also, at that distance, atmospheric conditions are going to govern a great deal of the path. As a result you're going to see a wide range of path loss variation as the weather changes. Sometimes the atmospheric conditions will be in your favor... but at least as often, not. On any given day the real and predicted NM on such a path could differ by well more than 10 dB.

For 100+ mile reception (which is DXing), fractions of signal make all the difference. Pre-amps add noise. Cable has losses. To avoid adding noise while avoiding cable loss, the tuner could be placed at the antenna. Then either a data stream or a video/audio signal is brought into the house; both survive long cable runs better than a weak signal from an antenna.

There are at least two ways that can be done:

1. Put a silicon dust HDHR in a weather proof enclosure up with the antenna. Run power and network to it.
2. Put a tuner box in a weather proof enclosure up with the antenna. Run power, and IR control to it; run video and audio from it. For HD, the best bet would likely be component which can be run through RG6 with RCA-F adapters. For SD, the CH3/4 modulator output could be brought down on coax. Audio could be run on coax with RCA-F adapters, as could composite video.

The advantage of that is other than a short coax jumper from the antenna (or balun) to the tuner, there is not noise being added by an amp and no loss from a long cable run. (A disadvantage is a potentially expensive piece of equipment is on the mast which could be a lightning rod.) The noise of any active electronics in close proximity to the antenna could be picked up by the antenna, so a shielded enclosure may be advisable.

You are probably not going to reliably get stations from 110 miles away 24-7-365. The best to hope for is seasonal luck and/or time of day luck. I have a station WBOC 85 miles away. It is co channeled pretty bad in my area. It is also 70 degrees off axis from where my antenna points. In the summer late at night and early in the morning it comes in well enough to watch. Something about the atmosphere is causing the RF21 signal to come in loud and clear even though the predicted NM is -11.3. A NM is -11.3 is quite doable, but WBOC is still coming in with off axis loss and preamp noise; my antenna should be 15 to30dB down on CH 21 70 degrees off axis.