San Francisco, CA - OTA - Page 101

For a couple of years I've struggled with poor and inconsistent reception of 7.1 and sometimes other SF channels despite various antennas, high poles, preamps etc.

I borrowed a signal strength meter with a primitive spectrum analyzer. It shows a high powered interferer at 532.25 Mhz about 30 db higher than channel 7.1. I assume that this has been the source of my troubles and confusion. I have not had a chance to see what direction it is coming from.

Has anyone a clue on what this might be? I'm in the Mountain View area.

Ends Dec 11.

532.25 mhz is the frequency of kgo tv digital
milt

Yes I am aware that it is A frequency that falls within the 6 MHz wide channel that is licensed by the FCC solely to KGO.

It is a 30dB higher interference signal not at the center of the channel and not modulated. It is not coming from KGO unless the whole of the bay area hasn't noticed it.

I can actually receive 7.1 KGO when I place my antenna in a very inconvenient spot (on the floor in front of my balcony door), but then I lose other channels such as 2.1 KTVU. So it's still pretty annoying. I wonder if a pre-amp would help increase the chances of finding a 'sweet spot' where I can get all the channels I want without having to move the antenna all the time?

You're most likely suffering from multipath, which varies from channel to channel because of the different frequencies. A pre-amp will only increase the strength of everything... the main signal and the reflections causing the multipath.

You need to get a directional antenna that blocks the reflections and you'll have much better results. Also, get the antenna as high as you can. Getting it outside will also help. Of course the roof of your home or building will give you the best results.

If you're stuck with using an indoor antenna, just find the best "sweet spot", although that spot might not be the most convenient or most appropriate for room decorating. A friend found the best location for his antenna to be atop his living room lamp. His wife did not approve. LOL

Larry
SF

I'm using the CM4228 mounted on a 10' mast and can pick up all the major networks and most of the minor ones. If you are fighting multipath issues, one thing to try is to angle your antenna up slightly. This changes the sensitivity profile to extend the forward range while reducing sensitivity in the reverse direction. bowtie antennas are pretty directional already but all antennas have some omnidirectional sensitivity. If you have enough room for a 4 bay bowtie like the CM4221 on your balcony, that's probably your best option. If mounting is a problem, then you can buy or build a cinder block stand with like an 8' mast. Assuming of course, that your balcony is facing in the right direction.

Now, since you mention that KGO-DT only comes in with your antenna on the floor (i.e. lower elevation), you might be having a problem with overload. It's possible that KGO is sending a stronger signal than the rest and thus causing the "when I get A, I lose B" situation. Before jumping to the preamp, you really need to figure out what the problem is. I have a pre-amp on my mast but found that if I connect it, most of my stations actually dissapear due to overload. When you put your antenna on the floor and get KGO, what's your signal strength? If KGO has high signal strenght but KTVU has low signal strength, then you might have an overload situation. Compare the signal strength with the antenna in various positions to see if you can find the sweet spot for all. BTW, you might also try pointing your antenna slightly off center as well. That can help with both overload and multipath situations.

Does anyone know what bit rate KPIX uses during HD broadcast?

Here's a spectrum analyzer image I took showing KCBA-DT with interference from KOVR analog, both on channel 13.

http://images.aa6g.org/ch35.jpg

KOVR analog shows up as two big spikes at the video and audio carrier frequencies. Is this similar to what you're seeing except your interference is 2.25 MHz above the bottom of the channel 24?

Assuming this is the case, somewhere nearby there is a device transmitting on 532.25 MHz. The only way to solve it is to track it down. A directional UHF antenna and the spectrum analyzer would get you pointed in the right direction. If you're lucky it will be in your own house.

Chuck

Yes, similar.

The spike is anything from 5-30 db's depending on the antenna (mis)pointing. I can make things sort of work with the antenna slightly off KGO and the spike down to 10 db's. The direction of rotation gives a slight clue that it may be coming from the bay side of 101.

The same spike is on my friends communal townhouse system too. He is quarter mile away. In his case about 10db above KGO. It would seam that receivers can handle that.

I drove around today with a non directional antenna. Very inconclusive but he highest reading was next to Microsoft where they butt against Moffat Field, NASA etc. Got -15 db mV with a six inch wire inside my car. Seamed to be detectable all the way to Palo Alto.

I need to borrow a real spectrum analyzer to eliminate any self generated interference in the cheap spectrum analyzer, but since my receiver agrees with the diagnosis I am pretty sure there really is some interference with significant power.

If you can determine what building it is coming from you can contact the people there and see if you can get it shut off. If not, I'd seriously consider contacting the FCC. Whatever it is, it is not legal. You can't be the only one being affected. Usually the FCC will respond to these sorts of problems.

Chuck

This is my first post on this just-discovered thread. I have a question (please be gentle as I show my ignorance).

I purchased my first TV since 1979. The Panasonic TH-42PZ700U was just delivered. It is a plasma HDTV.

I live in Kensington in the Berkeley Hills 14.2 miles from Sutro Tower, which is visible across the bay's waters. Over-the-air (OTA) signals are my sole source--and will remain so (I fear).

Trusting what I read about how good OTA is for receiving digital and High-Def TV (and really having no other choice), I hooked the set up to my sagging 20-year-old El Cheapo Radio Shack roof antenna . . . and held my breath.

After reading on this thread about all the problems people hereabouts were having, I didn't have much hope. Also, I had to use a splitter on the coaxial coming from the roof, so that one shorter coaxial cable could go to the VCR and another to the TV. (I had read that my signal would be cut in half. True? That's not my question.)

Well, I'm happy to report that I'm receiving several dozen analog and digital stations. And some are . . . WOW!

I'm receiving more stations than antennaweb.org predicted for the "yellow" antenna, but few or none for the "blue." I'm also receiving more stations than TVFool.com predicted.

I had read here that I should anticipate multipath interference from the lovely hills we have gracing the bay area. But the signals are very clear, except for some slight ghosting on some of the analog stations. (Maybe that's the dreaded MULTIPATH monster.)

Now, to my question. When I first hooked up the TV, almost all the major broadcasters' signals were at 100% on the TV's built-in signal meter. Only one network station (NBC) was lower, and it was 92%. I was in reception heaven!

A couple of days later when I checked again (because channel 5.1 was sputtering and breaking up briefly). This time a couple of channels were still at 100%, but many stations had now dropped to less than 100%. Most were in the 90s, but some had dropped to the 80s.

Question 1: Given this admittedly brief experience, am I to expect that my signal will vary? Why? Weather? Other appliances? The gods? Anything to be done about it?

Question 2: When channel 5.1 had a few brief breakups, I heard a sharp POP! from the TV each time. Is that harmful to the new set? Should I surf away from a station that gives those popping noises?

Dawn--

Congratulations on discovering HDTV and AVS Forum!

1. Yes, your reception is likely to vary somewhat from day to day. You may reduce this by replacing your antenna with a more directional one (or you may not--the gods [or is it poltergeists?] seem to have something to do with this).

2. Your TV set should not suffer any maladies from tuning weak/m.p.-laden signals, so I would only worry about your speakers, which could suffer damage if the POP is rendered at sufficient volume. Realistically, little bad is likely to occur from these.

P.S.: I used to live in El Cerrito, just up The Alameda from you. Great views you have there, as long as the fog isn't in.

It sounds like you've done your homework and you don't sound ignorant at all. No need to apologize for that! LOL

I'm not sure what it is that causes the signal levels to change, but they do. Weather, wet ground and trees, fog... who knows... but you will see some fluctuations.

You're old antenna seems to still be holding in there and doing a decent job, but I think you'd do better if you replaced it with a new one with a little more gain. Everyone around here seems to have very good luck with the Channel Master 4228, which is available at Fry's Electronics. A new antenna with new coax will probably make enough difference so that you won't see that occasional break up.

I have a 4228 and can receive stations that are 35 miles away with no problem, plus a few that are 65 miles away transmitting from Walnut Grove up in the Delta, so it's a good antenna.

As Mr. Peterson said, the only possible harm from those pops would be to your speakers, and only if you had the volume up pretty high.

You guessed right about the multipath. On analog stations it shows up as ghosts. On digital stations it reduces signal quality... which is what your signal readings show. The signal readings don't really show strength for digital, but quality... a combination of strength and clarity. Multipath can reduce the signals, and if it gets real bad your levels will drop way down and your picture will disappear. If you only have a few ghosts, you aren't being bothered by much multipath.

Enjoy your new HDTV!

Larry
SF

This is not a reception issue to the best of my knowledge. I've been seeing this issue with KPIX's digital signal for many months, if not longer. I say it's not a reception issue because I get this problem whether watching the signal OTA or whether watching Dish Network's retransmission of the same signal. It primarily, possibly only, happens during local broadcasts as compared to CBS network broadcasts. The signal freezes momentarily, sometimes displaying a pink screen, and then the sound comes back loudly at first before settling down to the proper level. I've noticed when this happens the audio indication on my A/V receiver briefly switches to Dolby Digital before switching back to the correct Dolby Pro Logic II which is what the receiver diplayed before the signal problem. This problem seems to happen at least once per half hour of local programming as I almost never get through their late local newscast without this problem occurring at least once.

I've never heard anyone else mention this problem before so I thought I'd chime in here to see if anyone else is seeing this. Anyone? Presumably this is an issue similar to what's going on with KGO's digital signal. There I see frequent picture breakups sometimes clearly displaying six quadrants on the screen. These breakups also frequently feature the color green being displayed in portions of the screen. I say these problems are related because they appear to be transmission problems rather than reception problems. Errors encoded in their transmission streams? Any thoughts from others regarding these two problems would be greatly appreciated.

bobli--

AFAIK, I've not seen either of the problems that you describe, but that may be because I seldom watch local programming on 5 or 7. But if you're seeing it regularly on 7.1 network programs then I'm pretty sure that you have either a reception or local hardware problem.

In case anybody has been wondering why they can't get anything from the sutro tower this morning, they are down and trying to fix some kind of problem. they hope to be up and runnin g sometime this afternoon.

Last night as I was channel surfing and enjoying my first days with my first digital TV (Panasonic TH-42PZ700U), I happened onto channel 7.1 and there was a very clear image of a split picture with the two halves reversed. (The right half was on the left and the left half on the right. Kinda cool really.)

My first thought was, "Oh! Oh! New set; big problem." I surfed away to other channels, which were all OK, then came back to 7.1, which was still split and reversed. After a bit of back and forth, the screen went faded blue and the "Channel Not Available" message appeared.

When I surfed away and came back to 7.1 in a few minutes, all was normal. The built-in Signal Meter even read !00%. It was an ABC program ("Boston Legal"), not a local program.

Question: Is this sort of image black magic something to be expected with OTA digital? Is there a remedy?

I'm using a sagging 20-plus-year-old El Cheapo Radio Shack rooftop antenna with maybe a 25-foot run of coaxial cable that then connects to a little digital splitter, which splits the signal to the TV and to the old VCR.

Have seen the KPIX local program momentary freeze for quite awhile, maybe over a year.
I see it on comcast ch. 705 when I watch peoples court and judge Judy. Must be a
problem with the equipment. I would think CBS could afford to fix it. Does anyone see
the problem on analog 5?

Only when the gremlins have taken over in the broadcast control room. Right, Larry?
The same one that we had back in the 1950s when NTSC TV was still new and we saw: "Technical difficulties. Please stand by."

Yeah, it's a problem with equipment...but whose? Can you record these freezes for analysis with TSReader or some such tool?

DawnSun: I've never seen the kind of reversed image problem that happened on KGO 7.1 last night during Boston Legal before. I first saw it on DirecTV from the satellite and then checked OTA, both through the DirecTV receiver/DVR and via the antenna connection on my TV. The problem was in all three (digital) places, but there was no such problem on the old NTSC channel 7. I too tuned to some other channels for a while and the problem had been resolved by the time I tuned back to 7.1.

I don't think this kind of thing is common. It's probably due to some kind of equipment problem at KGO.

WHEW! Thank you, Ron HD.

I'm happy to hear that someone else saw the same thing. When one has a brand new set--and technology (new to me)--as I do, one suspects that every problem encountered is a flaw in his new equipment or his lack of understanding how to manipulate it.

I'm still tip toeing through the first 100 hours of plasma break-in, not strickly required, I know, but I'm just obsessive enough to follow the recommended protocols--to a point. At least I didn't get the break-in DVD!

Thank you, too, TPeterson, for the good-humored reassurance.

WHEW! Thank you, Ron HD.

I'm happy to hear that someone else saw the same thing. When one has a brand new set--and technology (new to me)--as I do, one suspects that every problem encountered is a flaw in his new equipment or his lack of understanding how to manipulate it.

I'm still tip toeing through the first 100 hours of plasma break-in, not strickly required, I know, but I'm just obsessive enough to follow the recommended protocols--to a point. At least I didn't get the break-in DVD!

Thank you, too, TPeterson, for the good-humored reassurance.

You're sure right about that! I'm sure they were fighting one of those gremlins there at KGO when you guys were seeing those backward images. If I had seen that, I wouldn't have had any idea what to do. "Maintenance!!" LOL

FYI, for the newcomers, I used to work as a Technical Director in KGO's Master Control before I retired. It's hard to believe, but this Saturday will be the 4th anniversary of my retirement! How time flies!

DawnSun... you're apt to see lots of weird stuff when watching your new TV... and much of it will be a problem at the station. It's gotten so things are running pretty smoothly lately here in SF, but there are still occasional problems.

I've seen that pink screen and then the audio level change on KPIX, too, but only when watching via Dish Network. I haven't seen it when viewing the OTA signal. I watch 5 mostly via the satellite though, because it's one of the two Sutro stations I have troubles with. KRON is the other one. Multipath is killing me on those two channels... a major problem when you're just 3/4 of a mile from Sutro. The signals are too strong! 2, 7, 9, 20, 32, 38, 44 and 66 are all okay.

The three stations on Mt. San Bruno, 11, 26 and 65, are far enough away that I don't have any problems with them. I only get three out of the four stations from the Fremont hills. 14, 36 and 48 are okay, but 54 is really weak and hardily ever comes in. 47 from Novato has a good signal.

I cannot get the stations further north...22 in Rohnert Park and 50 in Santa Rosa, nor 42 from Mt. Diablo. 42 analog is fine, but I can't get the digital.

I can get one station from Sacramento in here solid 100% of the time... KMAX 31... at a 68 to 70 reading. I have never been able to receive any of the other digital stations from up there though.

All of this is with a Channel Master 4228.

Everyone have a wonderful Christmas! Enjoy your HD!

Larry
SF

Thanks Larry.

Although I receive the main broadcast channels with my 20-year-old roof antenna, I'd like very much to receive channel 54 and 22, both PBS which is the main source of TV for us. And maybe there are other stations I don't know about.

According to antennaweb.org, channel 54 is at compass bearing 127 degrees, while the Sutro stations are at 207 degrees. (Channel 11 is at 194 and 65 is at 141--and I get both.)

Question 1: With a directional antenna such as Channel Master 4228, would I have a more reliable signal and possibly more stations? I would only be able to aim it in one direction, of course.

Oh dear! I just (11:55 a.m.) turned on the TV to be able to report accurately to you what channels I can receive with the old roof antenna. Suddenly this morning I can't receive most of the digital channels!

No image for any of the digital channels connected to 2, 4, 5, 7, 9, 20, 32, or 44. I do receive the digital channels connected to 11, 26, 43, 65, 66, and 68. Also, I can receive all the analog channels. All these channels were there last night.

Question 2: Does this mean one of the towers is out for digital only? Or did the storm last night do something to my antenna? Or is this sort of thing also to be expected?

Double post: Oh, sorry about the double post earlier. My firewall doesn't like AVS Forum, so I have to disable it to do anything, even change pages! A drag, and I must get rid of that firewall and download another (free) one.

There appears to be some kind of problem at Sutro tower, which is where all these channels originate. Someone over at DBS Talk reported that there may have been an incident with a backhoe cutting some cables -- exactly why this would cause all the DTV stations to go off is unclear. I guess all we can do is STAY TUNED!

There was a notice yesterday from Red Dana to her KQED DTV newsletter folk saying that the Sutro DTV stations were off the air for some (undefined) "maintenance". She said that they hoped to have them back on the air by 5 p.m. last evening. I suppose that their being off again today means that they didn't finish whatever the maintenance job was yesterday.

It looks like all the Sutro DTV stations are working again.

First, a note about the shut down of the digital stations at Sutro. The reason they have to go off the air occasionally is because they don't have any alternate antennas yet. When they have to do work high up on the tower the analog stations switch to their alternate antennas down low ( See Sutro Tower diagram: http://www.larrykenney.com/sutrotwr.html ) and the digital stations have to be shut down. The RF would fry anyone working up there.

It would be nice if the stations would let the public know about these shut downs in advance. They're informed, in advance, by Sutro Tower management, so they could put something on their web site about it. There are enough people using digital tuners now that a shut down affects a lot of viewers. It would keep people from wondering if something's gone wrong with their new HDTV!

Red Dana of KQED occasionally sends out a notice about the shut downs to those who have signed up for their digital TV announcements, but it's usually after the fact.

This will surely all change after the analog shut down when the antennas for the analog stations are removed and there's room for alternate antennas for the digital transmitters. There will be lots of changes to the antennas up there. The VHF antennas for channels 2, 4, 5 and 9 will no longer be needed, and I suspect that they will be replaced with permanent UHF antennas for these stations' digital transmitters in place of the combined antenna arrangement now being used. Channel 7 will be the only station that will be operating on VHF from Sutro Tower after the analog shut down. All of the other stations on Sutro will be on UHF.

Now on to DawnSun's other questions...

The CM 4228 is quite directional, so you'd need to use a rotor if you wanted to receive KTEH 54 and KRCB 22. I don't know if you'd be able to get them or not, because neither one has a very strong signal. Does antennaweb.org show them in your list? I can't get them here in San Francisco. KICU 36 and KTEH 54 transmit from the same tower on Monument Peak east of Fremont. I get 36 with no problem, but 54 is NOT received about 95% of the time. 54.1 has exactly the same programming as 9.1, though, so no big loss. I've never received 22 from Rohnert Park.

Larry
SF