Fractal Antenna for DTV Over-the-Airheads

[xmellman]

So, maybe my antenna just isn't cutting it? It's about 14 or 15 years old from Radio Shack. It's one of those mast-mounted units with the fold-out arms. It's gotta be 6' long and 4' across I would guess. It's in my attic above the second story of my house. I would think it would be more than sufficient to pull in these signals. Connected to the antenna is the balun. I have a splitter in the attic - one side goes to the TV upstairs, the other to the one downstairs. The coax cable is pretty long to the downstairs TV. All of that said, I took the converter box and a small hand-held TV up to the attic to eliminate the variables of the cable lengths and the splitter. I hooked the box directly to the antenna with a 6' cable. I think I got a channel or 2 that I am not getting with the splitter and longer cables, but they were weak anyway, so I assumed that the splitter and cable were only giving me a small loss. Any other suggestions?

[SingSing]

The stations at -60 dBm or less are difficult to pull in without an Amplifier.
-60 dBm is 1 nano Watt.

[edDV]

The one station you have line of sight (LOS) is 18. The rest are behind a hill (1Edge, 2 Edge).

You will need a roof mounted antenna or if in attic, a larger antenna. you need an antenna tha covers both upper VHF and UHF up to Ch43 (ABC). A good starting point would be one of the Wineguard 769 series.
There are four sizes from HD-7695 (Red Zone) to HD-7698 (Blue Zone)

http://www.summitsource.com/winegard-hd-7695p-high-definition-vhfuhf-hd769-series-ante...le-p-6788.html

http://www.solidsignal.com/prod_display.asp?PROD=HD7697P

http://www.summitsource.com/winegard-hd7698p-high-definition-vhfuhf-hd769-series-hdtv-...-2-p-7316.html

[edDV]

Lake Oswego always has been a tough TV reception area. You are fighting these hills.

[xmellman]

What a great forum. You people are awesome.

The above image is marked on the east side of LO - I am on the west side (a little to the west of where you see Kruse Way and Boones Ferry Rd. on the map, so, even worse, I have Mt. Sylvania (Mountain Park) smack in my LOS.

It looks like the channels I care about are all in the UHF spectrum. Is there a good UHF-only rig that might work in my attic?

Thanks for all the great help!

[edDV]

http://www.solidsignal.com/prod_display.asp?PROD=AD-91XG

This will get nothing on VHF.

BTW, VHF bends around hills better than UHF.

[SLK001]

The splitter is taking at least half your power. A long cable run can take the other half, leaving you with, well, nothing (JUST KIDDING)! No, a long cable run can consume 2 to 3 dB of what is left, leaving you with very little left. You might want to put a mast mounted amplifier with a built in splitter in your signal path. Twin lead has lower losses than cable, so you might be able to run that instead of a cable.

You might also want to look into getting a higher gain antenna, because of all the parts in the receiving path, the antenna is the most important. An excellent amplifier hooked up to a poor antenna will give you bad results, because you simply can't amplify signals that aren't there.

[usually_quiet]

I looked at post-transition frequency assignments for Portland. These will be VHF again at some point:

KOAC DT PBS 07
KGW- DT NBC 08
KOPB DT PBS 10
KPTV DT FOX 12

Are you not interested in any of them?

[xmellman]

Yes - I am definitely interested in those post-transition VHF stations. This is what I have been really trying to figure out because my VHF reception is already good. Will any of the other "majors" go back to VHF, or is this the final list?

[usually_quiet]

Yes - I am definitely interested in those post-transition VHF stations. This is what I have been really trying to figure out because my VHF reception is already good. Will any of the other "majors" go back to VHF, or is this the final list?

Those were the only ones I saw for the actual Portland market. (I used the RabbitEars website)

If you enter your address at www.tvfool.com again, there is a set of buttons to view your post-transition reception on the same page as for the graphic you posted. That should tell you what you can get in VHF.

[edDV]

Yes - I am definitely interested in those post-transition VHF stations. This is what I have been really trying to figure out because my VHF reception is already good. Will any of the other "majors" go back to VHF, or is this the final list?

I used the final list from rabbit ears, not what is currently on air.

In most markets lower VHF channels (Ch 2-6) are being abandoned due to poor ATSC performance. These only work well over water (e.g. Miami). Only 20 broadcasters out of ~ 1700 chose to remain on Ch 2-6 although those channels are still being used for rural analog translators.

[tmw]

I finally finished my ruckman-style fractal antenna last night, since the transition was supposed to occur (I'm still getting all my analog stations). I used the same RadioShack box and design as his site (4 "stars" with 60 degree bends), using electrical wire to make the fractal things. I made it fit within the box, just for aesthetic reasons.

I find the reception is good considering the size (only 6" x 8"), but still only on par with the rabbit ears. I'll have to post some pictures tonight. I'm only 5 miles away from the major transmitters, so it's not an issue.

I also have an amplified antenna, and found something strange. The amplified antenna worked really well when the power was turned off (possibly because it has really large rabbit ears). However, when I turned on the amplified, the tuner box immediately lost the signal.

I'll post some more details and pictures of the antenna when I get a chance. Does anyone else have experience with similar attempts?

[edDV]

I finally finished my ruckman-style fractal antenna last night, since the transition was supposed to occur (I'm still getting all my analog stations). I used the same RadioShack box and design as his site (4 "stars" with 60 degree bends), using electrical wire to make the fractal things. I made it fit within the box, just for aesthetic reasons.

I find the reception is good considering the size (only 6" x 8"), but still only on par with the rabbit ears. I'll have to post some pictures tonight. I'm only 5 miles away from the major transmitters, so it's not an issue.

I also have an amplified antenna, and found something strange. The amplified antenna worked really well when the power was turned off (possibly because it has really large rabbit ears). However, when I turned on the amplified, the tuner box immediately lost the signal.

I'll post some more details and pictures of the antenna when I get a chance. Does anyone else have experience with similar attempts?

At 5mi you are proably overloading with amp off. RF follows the square law for radiated power attenuation.

[SLK001]

Unless your amplifier is shielded very well, you're probably too close to the transmitters to use it. At 5 miles, you could hang dental floss on the antenna inputs and still get blown away with signal.