Combiner for two antennas

[tom baker]

I don't have cable - but have an antenna and get good reception from Seattle. I want to add one station from Tacoma which is off about 45 degrees. The stations used to be VHF and UHF but not sure now with the conversion to digital what frequencies are anymore. Is there a combiner I can get to work with the two antennas?
Will I need an amplifier due to more signal loss?
I would prefer good quality gear and not the stuff from "Radio Hut".
Thanks

 

[iwire]

How about an old school antenna rotator?

 

[sgunsel]

I'd try aiming the antenna midway between the two directions and see what happens. Maybe move it a bit either way for best results. Most antennas are not too directional and will receive from more than one direction if not separated by too much, 45 degrees might be OK. If both signals are relatively stong, you should get both OK. I have a fairly large TV antenna on my roof and it will bring in stations within 45 degrees separation.

If you can't get both from one direction, try aiming diectly at Tacoma and see if it comes in OK. I'd try this next as it is simpler and more reliable than another antenna, plus you will at least determine if reception is even feasible. If you add a second antenna, an unamplified splitter/combiner will introduce loss.

If still no luck, you need a bigger/higher antenna, better coaxial cable, an antenna amplifier (at the antenna), or all of these. You will happiest with one antenna.

Only the low VHF channels are gone. Your antenna should continue to work as well as it did.

 

[hillbilly1]

Channel Master 7777 amplifier has dual inputs for two antennas, though they are actually one for VHF, and the other for UHF, you just don't get as much gain trying to get UHF on the VHF input, use that input on the stronger stations. Some of the digital channels are on VHF, but most are on UHF. You can get the amp from Crutchfield.com or Fry's Electronics if theres one near you. The bow tie fringe UHF antennas work the best.
http://www.frys.com/product/5820193?site=sr:SEARCH:MAIN_RSLT_PG

http://www.frys.com/product/5989664?site=sr:SEARCH:MAIN_RSLT_PG

 

[egnlsn]

To combine an antenna for a single channel coming from a different direction, you should use a Channel Master JoinTenna for that single channel. It has a broadband input that passes everything BUT that one channel, and an input that passes just that one channel.

 

[hurk27]

Our area is between two TV viewing areas, South bend and Chicago, we have been using UHF kicker antennas for ever here because of this, common is a highly directional high gain UHF Yagi pointed at South bend and a all band VHF-UHF Yagi pointed at the south side of Chicago generally these are just combined at the mast and sent down one coax, some are amplified but for the most part un-necessary if a good quality high gain Yagi is used.

Prier to digital analogue signals were being transmitted for very high powered transmitters (50KW-3MW UHF) because it didn't take much interference to cause a bad picture, any noise or RFI in the area of the receiver would be affected, also buildings hills and even trees would cause ghost and picture fading in and out, amplifying the signal would in most cases just amplify the noise and problems as the video part of the transmission was AM (amplitude modulation) and was very subject to noise, while the audio was being sent by using FM (frequency shift modulation) which you can amplify and clear up to a point.

Now for digital:
Digital eliminated all these problems along with requiring high powered transmitters, since the receiver is only looking for 1's and 0's noise is no longer that much of a problem with error correcting, correcting the stream as it is being sent, two things interference is almost non-existent, and amplifiers are very effective if bringing up the signal to a usable level, transmitter power has been reduced to about 1 tenth of the normal stations output, but its surprising how far you can receive a digital signal with not much of an antenna, my sister has a tower that was put up back in the day of analogue when it was very hard to get even a clean signal from Chicago, now with digital she receives stations from all over, Detroit, Grand Rapids, Indy, and more, she has a rotor of course, I think we counted 145 stations in all, where before in analogue we might had 27 stations.

So after saying all of this, depending upon the distance between the transmitter and receiver and how many obstructions, using a good wide band yagi pointed between the two stations might bring in both stations if the gain is not to high, higher gain yagi's will have a smaller frontal lobe which will narrow the receiving area, if the signal level still causes image freezes then try a good adjustable gain amplifier I would suggest something with between 10-20db gain, if the distance to the transmitter is still to far or has hills or mountain blocking it, then you might have to break down and do a dual antenna set up with higher gain antennas pointed right at each transmitter, Google Earth has almost all transmitters located so you can get a direction using the measuring tool, if you need help finding them in GE let me know.

 

[hurk27]

Tom I did some playing around in GE today, thought I would post the results, not being sure where your are, I went by your location.

Start point 47?33.956'N 122?38.882'W
Channel, degrees from start point, miles from start point, ground eleavation at tower.
31 ,71.85? ,14.59m , 430'
38
48
_______________________________________________________________
39 ,70.89? ,14.38 ,415'
_______________________________________________________________
33 ,97.37? ,32.01 ,2827'
42
44
50
_______________________________________________________________
27 ,162.27? ,20.80 ,412'
_______________________________________________________________
13 ,259.38? ,7.02 ,1677'
_______________________________________________________________
14 ,260.56? ,7.54 ,1663'

does this help?

 

[hurk27]

I found 5 more stations you shouldn't have a problem with reciving:

Channel, direction from start, miles from start, ground elevation at tower

9, 77.62?, 16.18, 412'
11 These are ones I missed in Seattle
25
_____________________________________________________________
19, 353.47?, 77.42, 2395'
35,
_____________________________________________________________

The two channels up north (19,35) on Orcas Island are on a high hill of 2395 feet, so at 77.42 miles they should be availble to you with no problem.

 

[grich]

Lots of good suggestions here...you will find patience and experimentation will make it work.

Here's a link to a chart with the area stations, their virtual channel numbers, and the actual "physical" channel they are transmitting on...
http://members.shaw.ca/nwbroadcasters/digitaltv.htm

Some thoughts:

Try the simplest first...aim the antenna between the target stations and see if you can get everything.

Make sure your antenna is in good order...a decent VHF/UHF yagi mounted outdoors is still the best in my opinion (it appears the Sea/Tac market has some VHF stations.) RG/6 for the coax, as mentioned.

Having a rotor would allow you to spin around north and perhaps see what's happening with the Canucks . It would be the best to have full control over things, especially with the terrain, but will the wife want to turn the antenna? :roll: I can't get her to watch HD cable because it involves an extra step...

Try to avoid amplifiers unless you absolutely need them...strong local signals can overload them and cause grief.

If you want to go with two combined antennas, try a simple combiner first, but you may have problems caused by signal reflections being picked up by the off-axis antenna and screwing up the main signal. If you do have trouble and only one station interests you in Tacoma, the Jointenna option is a good one to avoid the reflection problems. If you search the AVS Forums you can find crazies who have stacked together two or more antennas in different directions and combined them with multiple filters to pull in stations from Des Moines, Waterloo and Cedar Rapids, Iowa. Des Moines can be a tough market because one station still operates on channel 5 (!?), and 8, 11 and 13 are also used.

Others I know use two coax feeds and switch them at the TV...not the best if there is more than one TV to feed.

Channel Master and Winegard are both good brands.

 

[GeorgeB]

Google Earth has almost all transmitters located so you can get a direction using the measuring tool, if you need help finding them in GE let me know.

There is a site which does far more than GE for this need ... go to TVFool (www.tvfool.com) where you can put your location in (to the nearest foot, almost) and get expected signal strength and direction. You can select a station and see signal strength shaded by mountains and other natural phenomena. GE is, I think, used for some displays.

For those of us who enjoy technology including RF and broadcast, you really should look at the AudioVideoScience forums. I read my local area thread and the DTV thread. I also scan the Technical forum. Links are

http://www.avsforum.com/avs-vb/showthread.php?t=322947 for Greenville SC
http://www.avsforum.com/avs-vb/showthread.php?t=823166 for DTV
http://www.avsforum.com/avs-vb/forumdisplay.php?f=25 for technical

The area threads seem to have 1-3 posts a day average, DTV about the same now that the transition is mostly complete. The tech one is more active (of course it is a forum, not a single thread) with perhaps 15 or 20 a day.

A young man at UVA maintains a website http://www.rabbitears.info/ with more fantastic support for our technology disease <g>.

ENJOY!

 

[tom baker]

All - Thanks for your help and Hurk27 for the maps. I had no idea that the transmitters were on google earth.
My wife will thank you when I get this to work as the station in Tacoma has shows she likes!