tigerbangs prescription for deep fringe reception

Tower Guy

I believe that your problem is interference.

CKTM-TV on channel 13 has a signal strength of -80.1 dbm at 23 degrees
WVNY-DT on channel 13 has a signal strength of -98.4 dbm at 164 degrees

In addition to antenna gain, you would need an antenna that has a side lobe pattern 141 degrees off axis that is at least 34 db below the main lobe. It's unlikely to get that with a single yagi antenna.

If you were to stack two identical yagi's side-by-side they can be placed so that the interfering signal would be out of phase. In your case this would be 52.33 inches apart.

It gets more complicated to consider that CFCF on channel 12 is 57.5 db stronger than WVNY's channel 13. A channel 12 notch filter or channel 13 bandpass filter will also be needed.

Intravino

I read on digitalhome.ca that some guys observed that when CFCF 12 was offair ( very rare because they are 24 7/7 ) their signal of WVNY-DT did not improve, anyways a notch filter would not make it worst.

How do you stack two 10y13s together? My 10y13s is on a J tube that is horizontally clamps to my tower.

They have to be exactly 52.33 inches apart?

Where is a good place to purchase a notch or bandpass filter?

You put the output of the two antennas in parallel?

Do you use 300 ohms cable to put the antennas together or 2 balums with 75 ohms coax or a splitter ?

Thanks again for your time,

Intravino

Tower Guy

The stacking distance is critical to null out CKTM. Use two baluns, two equal lengths of RG-6, a two way splitter, and get the balun phasing right by trial and error.

Interference from CKTM will prevent reception of WVNY even when CFCF is off the air.

Filters can be bought from Tinlee in Toronto, Microwave filter in Syracuse, NY or CE filter in Syracuse, NY.

Attached Images

WVNY.PNG (214.3 KB, 22 views)

Intravino

What do you mean by balun phasing?

Also, how would you mount the two 10y13s on a horizontal pole attached to my tower?


Thanks,

Intravino

BrianO

Yes. WCAX is the CBS affiliate in the Plattsburgh-Burlington area and it has been since the 1950's.

Tower Guy

balun phasing is covered here:
http://www.hdtvprimer.com/ANTENNAS/16bay.html
To mount the two antennas I'd use a mast as a cross arm, build two extensions for the ends with another mast cut down to about half a meter, drill two holes in each for TV U-bolts
Look at the picture here:
http://www.kyes.com/antenna/stackluge.html

They have the antennas above the crossarm. I'd do it below.

Intravino

Thanks a lot Tower Guy and also Brian.

That I think his going to be a project for spring.

Thanks Again,

Intravino

rrandolph

I am having trouble receiving the OTA signals. I am close to the transmitters, but there is a ridge in the way and I am surrounded by heavy forest (75' - 100' firs and maples). Should I spend money trying to receive the OTA signals, or is it a lost cause?

I think my antenna does OK considering I currently can pull in frequencies 4 and 39 (if I point the antenna the correct direction for 39 -- there is no close ridge in my way for this station). I would have to raise the antenna well over 100 feet to clear the trees that are near the house. Ghosting and noise are real problems with the analog stations, with the UHF being extremely snowy.

I don't care about 39 long term because I want the Portland PBS station (since it is the same direction as the other stations), but it tells me something about my antenna.

I attached some jpegs showing tvfool maps for frequencies 39 and 46, and a photo showing my antenna being dwarfed by my trees (photo looking towards the transmitters). You can see there is a shadow where I live for

I may order the 7777 and see how things go. If that works, then I will look into antennas that would work well eliminating the reflections. Any opinions?

Longitude: 45.5800
Latitude: -122.8155
134xx NW Old Germantown Rd
Portland, OR 97231
(Zip alone is way off -- use address or longitude and latitude)

Currently transmitting
Call-Sign Network Heading Miles Frequency
KPXG-DT ION 120° 5.9 4 (Currently receive well with antenna pointing many directions)
KOPB-DT PBS 122° 5.2 27 (signal never strong enough to decode)
KPTV-DT FOX 123° 5.2 30 (signal never strong enough to decode)
KOAC-DT PBS 182° 68.6 39 (Can receive if I point my antenna south with occasional drop-out)
KOIN-DT CBS 121° 5.9 40 (signal never strong enough to decode)
KGW-DT NBC 122° 5.2 46 (occasionally get a picture, weak signal)


Post February Transition (all the local stations will be broadcasting from the same set of towers).
Call-Sign Network Heading Miles Frequency
KGW-DT NBC 122° 5.2 8
KOPB-DT PBS 122° 5.2 10
KPTV-DT FOX 123° 5.2 12
KOIN-DT CBS 121° 5.9 40
KATU-DT ABC 121° 5.9 43

Attached Images

	tvfool_freq39.jpg (37.9 KB, 29 views)
	tvfool_freq46.jpg (32.5 KB, 25 views)
	house_photo.jpg (151.6 KB, 30 views)

tigerbangs

Under NO circumstances order a preamplifier: your TV signals are WAY too strong at your location. You appear to have a Radio Shack VU-75 which has almost no ability to reject multipath. You need to replace the antenna and caling with newer and more directional equipment to solve your issues. I cannot tell from the orientation of your antenna if you have aimed it in the right direction, but all of your channels come within a couple of degrees of one another, so you shouldn't need to rotate the antenna if you have everything working well. Since multipath is an issue in your location, I suggest that you consider a very directional VHF antenna like a Winegard YA-1713 plis a high-quality, very directional yagi-type UHF antenna like an AntennasDirect XG-43 or an XG-91. Use new coaxal cable and new bauln transformers. Join the antennas together into one coaxial cable using a UHF-VHF joiner like a Winegard CA-7700, and be sure to aim the antennas VERY carefully: this should solve your problem.

__________________
Real men don't use indoor antennas; neither do real women!

hoopitup2000

rrandolph,

My situation is very similar to yours.(18 stations within 6 miles, a ridge between us, lots of huge mature trees right in front of the antenna) I've done exactly what Tigerbangs has suggested for you and it works wonders. The multipath is so bad here that the only good reception I was ever able to get before was by laying an antenna right on the ground. This unamplified system far exceeds my expectations with the antenna just 12 feet above the roofline.

jbabb

OK finally got all the components installed for my system. I use an Antenna Craft U8000 with a wine guard 4800 pre amp. it is installed at the top of a 30 ft tower. install a channel master rotator also as I have stations 360 degrees of me. my zip code is 28327 is there anything else I can do to tweak and improve my reception I am still getting some drop out on some stations.
wwmb 21 is one of the channels I want but can't seem to get the channel show up but get only an intermittent signal. same for the sub channel 21.2 which is CW PLUS and has some good shows.

Attached Images

	Radar-Digital2.png (118.1 KB, 13 views)
	Radar-All2.png (122.8 KB, 7 views)

hoopitup2000

jbabb,

I see 2 things that are causing problems for you

1. You have "way" too many strong signals for the Winegard 4800. Things may improve after the analog shutdown; but it's still more pre-amp than you need. If you are only running 1 TV & less than 100 feet of RG-6, you may not even need a pre-amp.

2. You have a lot of adjacent channel issues. I personally would have chosen the more selective 91-XG for your situation; since you have a rotor.

Can you try bypassing the pre-amp and see what happens? Try your analog stations, and let us what you see.(Any ghosting, or interference)

jbabb

I get no analog at all with this antenna it's pretty much all snow and has been this way with other antennas UHF/VHF as well that's why I have always gotten my locals from Dish. but figured if I can get more off air why pay for it.it picks up 39 digital channels some better than others. but thought I would try to see if I could get them all to come in, I have 6 ft of quad shield from the antenna to the pre amp 100ft of quad shield coax from the top of the tower at the pre amp to the power injector in the house then 2 ft to the converter box and 2ft to the dvr and then 2 ft to the tv for a total of 112 ft of coax .

hoopitup2000

I was basing my comments on your zip code center; pre-transition results. After looking at your exact address post transition; you look to be OK with the 4800 for digtal reception.

I think the 91-XG would be the only thing that would substantially improve you results for the marginal stations you are going for. The U800 is only rated as having 12 db of gain.

rrandolph

Thanks for the answers -- you've given me hope!

The Antennas Direct website doesn't have too much technical info on their antennas. I am assuming that the XG91 will be slightly better at receiving the main signal relative to the multipath, and thus the extra money for that one would be worth it?

I looked for the coupler, but the Winegard 7700 and 7750 are discontinued. They make a CC7870, but it has a 3.5db loss. Is there something else you would recommend, or should I go with the CC7870?