Antenna advice

mahohmei

DTVUSA Jr. Member
#1
I'm trying to get the big five local channels: ABC, CBS, Fox, NBC, and PBS. According to tvfool.com, all five of these stations are between 19.8 and 24.8 miles from my house, LOS, and have power ratings between -27.7 and -34.1 dBm. I'd like to receive the channels on my TiVo Premiere.

I'm using an AntennaCraft 5MS921 "flying saucer" omnidirectional antenna atop a 10' mast, so the antenna site about 8' above the chimney, which is the highest point in my one-floor single-family house. We're in a 1-acre-lot subdivision, surrounded by trees that dwarf my house and antenna.

The wiring from the antenna to the TV is, I'd estimate, around 100 feet total. From the antenna, it goes through one F-coupler where I moved the antenna further up and didn't want to rip out the nail-in brick coax clamps, one F grounding block, one Leviton coax surge protector, and the antenna power injector.

As we stand right now:

- Two of the channels come in clearly,
- One of the channels comes in, but keeps cutting in and out, resulting in pixelation.
- One of the channels shows that there's something, but the TiVo can't get a picture.
- One of the channels doesn't come in at all, and the TiVo shows zero signal.

As an experiement, I bought a 15 dBm antenna amplifier from RadioShack, and it _did_ provide improvement on the channel that cuts in and out now--previously, it wouldn't even show.

Is there something I'm missing here or a way to improve this? For appearance reasons, if I am to have an outdoor antenna, it has to be a "flying saucer", but I'll put any ugly multi-element antenna I want in the attic. Our roof is plywood with asphalt shingles, and the attic gable ends are wood.

Any input is welcome here.

Thanks!
 
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#5
As much as I would like to hate the UFO antenna. I do think it should work at your location. The Antennacraft 5MS921 has a built in amplifier if the coax does not pass power as could happen with a bad connector, coax, or power supply the antenna will not work. As strong as signals are predicted to be at your location amplifier overload is a possibility if the amplifier is working. The other possibility would be some kind of severe signal blockage or multi-path caused by near by buildings or trees. I would to suspect that there is a problem with coax, power supply, power injector, the amplifier itself, or amplifier overload. Keep in mind in order for that antenna to work there can be nothing in line between the power injector and the antenna that might block power. With signals as strong as predicted amplifier overload is possible, and some reception is possible even with an un-powered or dead amplifier blocking signal.
Antenna suggestions based upon you TV fool report.
Stellar Labs HDTV 40 Mile Yagi Television Antenna | 30-2410 (302410) | Stellar Labs
Stellar Labs HDTV 30 Mile Bowtie Television Antenna | 30-2420 (302420) | Stellar Labs
Steve
 
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mahohmei

DTVUSA Jr. Member
#7
The thought just came to me that the coax coming in from the antenna goes through a coaxial grounding block, which is solidly connected to ground (10 AWG copper wire taking a 70' trip to a pipe clamp on the electric meter conduit). This grounding block is *between* the DC power injector and the antenna. Could the grounding block be getting in the way?

I did all the compression connectors on the cables myself, and they're all solid.

Also, our neighborhood has a *lot* of trees. All higher than my house. Massive trees in every direction.
 

MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#8
all your major networks are to the NE, except PBS 32, which is to the SW, almost 180 degrees apart (CW 24 is near there, too). All strong, green signals and UHF

I don't think we need any amplification here, you have enough signal strength. I would suggest one of the hinged 8 bay antennas like Antennas Direct DB8e or Stellar Labs 30-2430 with one section pointed NE and the other pointed SW. Yea, it's a lot bigger than the Omni, but it will do the job.
 
#9
The 5MS921 is an antenna I personally would not recommend. They are used a lot in my area I've not talked to anyone using one since the digital transition. In the past I was told by both users of the antenna, and a Radio Shack employee that they work very poorly. Looking at your TV fool report showing the very strong signals led me to believe there is something wrong with the antenna, related hardware, antenna placement, or nearby blockage of signal. The grounding block does not block DC voltage on the coax. There are two warnings in the instructions about not placing splitters, amplifiers, or other devices in the coax between the antenna and the power injector. I've learned from experience to use an ohm meter to check coax for end to end continuity, and shorts before installing. I prefer to use an analog meter as I'm not trying to make an exact measurement of resistance just a simple test of continuity. A single strand of incorrectly misplaced coax braid can kill the whole cable. I know to always check my own work, but until recently I've always trusted the pre-made cables. I now know that was a mistake. I approached posting on this thread with first offer advice on trying to make what you have work, then offer other ideas on what might work. Using a home brew antenna approach is a very good idea. It is possible to build a very good bidirectional UHF antenna out of simple hardware store parts from plans that are not difficult to find. The ones that come to mind are the Gray Hoverman, Kosmic SuperQuad, and Mclapp 4 bay. When properly constructed following the proven dimensions, and using no reflector these designs offer good bidirectional gain which can be useful in some areas.
http://www.dtvusaforum.com/dtv-hdtv...9-kosmic-antennas-superquad-4-bay-bowtie.html
DIY TV Antennas 4 bays, 2 bays, Kits and more
Single Bay Gray-Hoverman (SBGH) Antenna : DIY TV Antennas
Techorator - A blog about tech and more: Homemade $20 super antenna out of paper and tape!
Elements should be mounted on suitable plastic not wood. Mounting directly on wood can degrade performance, and not all plastics are RF transparent. I have personally has very good luck using the simple Mclapp 2 bay. It is easy to build and in some locations is all the antenna that is needed.
2 Bay Kit
No manufacturer has seen the need to offer a good, reasonably priced, compact bidirectional antenna, but they do persist in marketing some very low gain, claim to be omni antennas. Most are not truly omni.
MrPogi's suggestion should work in your location. I have no idea how assembly of the 8 bay antennas in a 180 degree configuration will go. I based my original antenna suggestions on size, price, predicted strong signals, and the possibility of the receiving the strong PBS signal off the back side.
Steve
 

MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#10
You could also mount two 4-bay antennas back-to back and couple them with a simple splitter (rated for outdoor use, of course). Another option, since the signals are strong, is to remove the reflector from one of the many available 4-bay antennas. This will involve unscrewing, cutting, or drilling out of the screws, bolts, or rivets holding the reflector on - a very simple modification.
 

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