Stacked TV antennas questions

Combining the coax output of the two antennas into a common splitter, then one coax to the switch should work OK as long as the signals are realatively strong. If not, you can always put an amplifier in the line. Both can be purchased at Radio Shack.

Instead of using a splitter and a switch, you would be better off just running the individual antenna leads to the digital box and TV. Then you would only be switching the TV, and not the TV and switch every time you wanted to change from digital to analog.

Dick - In view of Mingus Mountain

** Posted from **

Although I mentioned that you "could" combine the two antennas into one lead, the reason you may not want to is something called "ghosting." The two antennas will be receiving the same stations, although not from the same direction. Signals can bounce off mountains, etc. and you will get two signals of the same station arriving at your TV at two different times, even though they are of different signal strength. This causes your picture to have a ghost appearance. For that reason, I would run separate coax leads from the two antennas and forget the switch.

Dick

** Posted from **

We're in the Mund's Park area, already have an amplifier inline, Flag Channel 2 comes in REAL strong, but even with the amplifier the repeater stations on Mingus Mountain are usually kinda snowy. Think my antenna is pointed more or less in the general direction of Mingus Mt., but now that I got the azimuth off the TVFool website, I'll have to get back up on the roof and point the antenna a little better. We were up there for the weekend a few weeks ago, brought the digital converter along to try it, was able to pick up digital signals for AZ- TV and Telefutura, hope I can do a little better than that with another antenna.

Jerry

As previously mentioned, combining signals form two antennas onto one downlead will not work in 95% of the cases as there are time differences in signal reception due to pickup of reflections. Even if there are no reflections, pickup of the signal on the back lobe of the antenna pointed away from the desired direction may add or subtract from the main signal.

Greetings Jerry..

Interesting situation but not unlike what has been going on for years in the south SF Bay Area (San Jose). Sutro Tower is towards SF for about 50 miles while KNTV (Channel 11) is the opposite direction right in San Jose - behind you. For several years (many years ago now), KNTV sold a small 2 element antenna that you could mount on your TV mast and point the opposite direction to your normal TV antenna. It worked like a champ and got rid of what Dick calls:

Reference: "Although I mentioned that you "could" combine the two antennas into one lead, the reason you may not want to is something called "ghosting." The two antennas will be receiving the same stations, although not from the same direction."

This is the laymen's term for multipath interference. Two paths instead of a straight line point A => B. That reflection comes in a bit slower than the original signal path, thus the delay results in a "ghosting" affect. This can also be quite noticeable on FM reception. Indeed, as a radio amateur, we can actually use it to our advantage by reflecting our signals off natural points!

Although we tended to use 300 ohm twin lead back in those days, you should be fine with 75 ohm coax. As Dick has mentioned, if you want the trouble and expense of two pieces of coax to run (really un-needed) go for it. Personally, I would either get an inexpensive rotator (programmable now days) with a remote for it and put up a nice single array OR go with two antennas and run the coax between them. I should also mention, a large number of apartment complexes across this country are doing the two antenna (or more) with a single lead in routine.

Cheers, Mr. Mentor

Jerry, be careful listing your actual e-mail address on Usenet, there are folks out here that you REALLY don't want e-mailing you! Just put in something bogus, it will take it! Notice what mine is...

My understanding is that KNTV 11 moved their transmitter site a couple of years ago.

The old site on Mt. Loma Prieta was shut down in 2006. The new transmitter site is on San Bruno Mountain, quite some distance to the north: coordinates 37 deg, 41 min, 07 sec, West Longitude: 122 deg, 26 min, 01 sec.

Back when the NBC affiliation was moved to Channel 11, I had to add a second antenna in order to pick it up properly (our primary antenna i a standard log-periodic/reflector aimed north towards Sutro). I made a single-channel Yagi for Channel 11, aimed it southwards, and merged the signal to the main coax using a "Join-tenna" single-channel combiner. Worked like a charm.

Doesn't work worth beans nowadays, since the Yagi towards Loma Prieta rather than towards Mt. Bruno, and the Join-tenna is blocking the Channel 11 signal coming in from the log-periodic. All we get on 11 is ghosts and snow. I need to go up on the roof, and either re-aim the Yagi, or just jumper out the combiner and use the northwards-pointing log-periodic for all channels - the beamwidth is probably plenty sufficient.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

Greetings Dave..

I did mention many years ago now.. To qualify that, how about back in the 60's & 70's. I see that stations and licenses have moved all around the place. Back in those days KNTV wasn't affiliated with anyone since they were an independent station. Consider,

Heck, I remember when KLIV 1590 (as I recall) in San Jose was playing top 40 rock and roll music - NOT exclusively news at all. In fact, I was one of those 15th callers after hearing a certain song that won me a Coke jacket as I remember. Too many years ago now but I AM curious how many San Jose folks would ever remember KLIV playing top 40 - probably not many these days..

Those small two-element antennas mounted under the larger TV log are still on MANY roofs in San Jose. Granted, probably not in the best of shape but they're there! The twin lead would come from the larger log down to the two-element Yagi, connect to it before going to the TV inside the house. After all the complaints of bad video, KNTV did something about it by offering these antennas - it DID work well! Further, it was a inexpensive solution. They sold them like hotcakes back in those days..

Regarding: "I need to go up on the roof, and either re-aim the Yagi, or just jumper out the combiner and use the northwards-pointing log-periodic for all channels - the beamwidth is probably plenty sufficient."

You should try (at least initially) to re-aim it and see if that resolves the issue. My bet, it will then work like a charm!! The beam-width on a two-element array is broad as a barn! In fact, if you were to only move it an inch or so right now, it would probably clear up considerably. You're probably picking up multipath off of Loma. Move away from that reflection point, and things will clear up substantially if not totally. My bet will be totally clear video.

Ah, the things we do to avoid purchasing an inexpensive TV antenna rotator..

Cheers, Mr. Mentor

| >Interesting situation but not unlike what has been going on for years | >in the south SF Bay Area (San Jose). Sutro Tower is towards SF for | >about 50 miles while KNTV (Channel 11) is the opposite direction right | >in San Jose - behind you. For several years (many years ago now), KNTV | >sold a small 2 element antenna that you could mount on your TV mast | >and point the opposite direction to your normal TV antenna. | | My understanding is that KNTV 11 moved their transmitter site a couple | of years ago. | | The old site on Mt. Loma Prieta was shut down in 2006. The new | transmitter site is on San Bruno Mountain, quite some distance to the | north: coordinates 37 deg, 41 min, 07 sec, West Longitude: 122 deg,

26 | min, 01 sec. | | Back when the NBC affiliation was moved to Channel 11, I had to add a | second antenna in order to pick it up properly (our primary antenna i | a standard log-periodic/reflector aimed north towards Sutro). I made | a single-channel Yagi for Channel 11, aimed it southwards, and merged | the signal to the main coax using a "Join-tenna" single-channel | combiner. Worked like a charm. | | Doesn't work worth beans nowadays, since the Yagi towards Loma Prieta | rather than towards Mt. Bruno, and the Join-tenna is blocking the | Channel 11 signal coming in from the log-periodic. All we get on 11 | is ghosts and snow. I need to go up on the roof, and either re-aim | the Yagi, or just jumper out the combiner and use the | northwards-pointing log-periodic for all channels - the beamwidth is | probably plenty sufficient. | | -- | Dave Platt AE6EO | Friends of Jade Warrior home page: | I do _not_ wish to receive unsolicited commercial email, and I will | boycott any company which has the gall to send me such ads!

Dave..

I should have mentioned that other than KSFO (560 kHz) in S.F. the local south bay news station back in the earlier days was..

Do you remember what it was?

KXRX was the south bay news radio station. Yes, I realize that it's not even in the state of Calif. these days. Nor does it have any history on its Web site. To be able to rack up some free flight time, my father flew the Peeper-in-the-Piper back in those days with the late Bob Hallman of KNTV Channel 11 weather giving traffic reports as my father flew. Later, Bob got his own license and started flying and reporting on his own. After referencing KNTV history on Wikipedia, I'm amazed to see no mention of Bob on KNTV alumni. I wonder if those records are just lost or the company just doesn't keep historical personnel files. With the transition of owners, I'll bet many a record is either discarded or lost.

This was about the time my father was flying - perhaps a year or so before:

Notice ALL the open space at then San Jose Airport - this was _before_ it became San Jose Municipal Airport.

Cheers, Mr. Mentor

|| >Interesting situation but not unlike what has been going on for | years || >in the south SF Bay Area (San Jose). Sutro Tower is towards SF for || >about 50 miles while KNTV (Channel 11) is the opposite direction | right || >in San Jose - behind you. For several years (many years ago now), | KNTV || >sold a small 2 element antenna that you could mount on your TV mast || >and point the opposite direction to your normal TV antenna. || || My understanding is that KNTV 11 moved their transmitter site a | couple || of years ago. || || The old site on Mt. Loma Prieta was shut down in 2006. The new || transmitter site is on San Bruno Mountain, quite some distance to | the || north: coordinates 37 deg, 41 min, 07 sec, West Longitude: 122 deg, | 26 || min, 01 sec. || || Back when the NBC affiliation was moved to Channel 11, I had to add | a || second antenna in order to pick it up properly (our primary antenna | i || a standard log-periodic/reflector aimed north towards Sutro). I | made || a single-channel Yagi for Channel 11, aimed it southwards, and | merged || the signal to the main coax using a "Join-tenna" single-channel || combiner. Worked like a charm. || || Doesn't work worth beans nowadays, since the Yagi towards Loma | Prieta || rather than towards Mt. Bruno, and the Join-tenna is blocking the || Channel 11 signal coming in from the log-periodic. All we get on

11 || is ghosts and snow. I need to go up on the roof, and either re-aim || the Yagi, or just jumper out the combiner and use the || northwards-pointing log-periodic for all channels - the beamwidth is || probably plenty sufficient. || || -- || Dave Platt | AE6EO || Friends of Jade Warrior home page: | || I do _not_ wish to receive unsolicited commercial email, and I will || boycott any company which has the gall to send me such ads! | |

That's certainly the easiest thing to do.

The Yagi I built is somewhere in the neighborhood of 6 elements... I decided I wanted some real gain and multipath immunity. I scaled down one of the multi-element beam designs from the ARRL handbook by around 10:1.

I was rather amazed when I tried it out. Even down at ground level, with nearby buildings and trees in the way, I got a very clear picture on 11 just by pointing it towards Loma. Up on the roof it works like gangbusters.

It has pretty good front-to-back rejection with deep side lobes, so yeah, I'm just getting a confused mass of multipath backscatter from Loma Prieta, nearby buildings, trees, and so forth.

Swinging it around towards SFO should certaily do the trick.

Oh, I've got one, and we used to use it quite a lot... but they don't play well in a household with two independent TiVo DVRs! We really needed to have "all the signal, all of the time".

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!