Sacramento, CA - OTA - Page 303

No change in signal strength here in Stockton.

KCRA is normal strength here. I would know if it was on the back-up site.

Chuck

I watched this week's episode of Revenge on two different AV receivers this week. One with HDMI, one with an optical cable. In both cases, the audio was really messed up. It seemed like most of the audio was coming out of the rear channels. The audio on most of the ABC shows I watch (Castle, Revenge) have similar issues. I have to cut the rear channel by 10dB.

This has been going on for some time on KXTV-HD during the 10:00-11:00 PM time-frame. Hard to believe that ABC is the cause of the crappy Dolby 5.1 sound. My guess is the smart KXTV technicians go home at 9:59 PM every night leaving either a faulty automated system in place, or perhaps semi-trained monkey).

I think I found out why I haven't been able to receive KCRA for the past few days while the rest of the Walnut Grove stations have been normal. I just received the following post from the SF HDTV Yahoo Group:

"I randomly flipped my workplace's DTV receiver in San Jose to RF 35 today and KGO (ABC) is transmitting there now."

It looks like KGO's translator on Monument Peak in the South Bay is desensing the signal for KCRA here in San Francisco. KCRA has normally been in the 20 to 22 dB range, but has been in the 13 dB range for the past three days. I was hoping that the KGO translator wouldn't affect my KCRA reception, but it looks like is.

Larry
SF

I was afraid this might be the case. The translator made your noise floor go up 8 or 9 dB.

Chuck

Hello,

I could use a little advice. I've recently decided to cut out cable and live off of the antenna, but the transition has not been completely smooth.

I live in South Sacramento and I am trying to use the ancient antenna that came with my home. I get all of the major channels except fine except for KCRA-3. I often get interference on that station with the picture freezing or getting strange artifacts and the audio cutting out.

I think the ancient antenna is pointing slightly southeast when it should be pointing slightly southwest. It appears to be a directional antenna to my untrained eye. There is also coax running all over the place from years of people using the antenna, then installing Dish, DirecTV and Comcast -- all of whom tried to use existing runs -- creating a giant mess of cabling.

The antenna looks a little bent, and the mast it is mounted to is busy rusting out. On the other hand, my roof is a nightmarish deathtrap. It is really tall and peaked, and currently wet and slipper. My brother opined that if I was going to go through the bother of getting up there to turn the antenna to point the right direction, I might want to think about going further.

I was considering junking it all, replacing the antenna and rerunning the coax to my three TVs, but I wasn't sure what I needed as far as antennas went.

I'd love to get more channels, but I don't think I care about that enough to rotate the antenna every time I want to watch Vietnamese bowling from Bakersfield or whatever.

What would be a good antenna for me to purchase that would get me the maximum number of OTA channels with no work after the initial setup? I figured I'd ask the experts before trying to work it out myself.

Thanks in advance for your help. TVfool plot attached.

That's an impressive list of channels that you could likely receive! The problem of course is that they're in many different directions. This comes down to how much effort do want to put into it? The Sacramento stations are extremely strong at your location and you don't need a big antenna. Something like this should work just fine for those:

http://www.solidsignal.com/pview.asp...tenna-(HD7694P)

If you want to have a better chance at more stations on the list you'll need a rotor. You might get stations from other directions with the antenna not pointed at them, but it'll be hit and miss.

From your description it sounds like you'd be best to scrap what you have now and start from scratch. The setup would be simpler. Do not use a preamp. The Sacramento stations are too strong for one.

Personally I don't recommend omni directional or indoor antennas if you have an outdoor option.

Come back if you need more help.

Chuck

So no omni-directional? That was what I figured was the safest route. My logic was that the Sac stations would come in strong regardless and that the omni-directional antenna might more easily pick up San Francisco stations that were coming in from other directions.

Thanks for the advice. I'll probably suffer through the winter and then redo the antenna system when it gets a bit warmer.

I've heard the opinion is that omni-directional antennas receive equally poorly in all directions....

They are low gain and are highly susceptible to multi-path, the bane of digital reception.

Is there a good website that explains the woes of fringe digital reception.... and why digital/8vsb doesn't work like the good ol analog days of snowy/ghosty picture yet very watchable? I tried to google it real quick but didn't come up with much.
I've had two people this week ask for my help; but I wanted them to know what they're up against before I provide any help. They're both older gents and probably used to the good ol analog days of receiving a bounced signal off the hill etc...
Thanks, Bob C

Most deep fringe folks didn't realize just how bad that snowy picture was, but they were still glad to have it....

This is the best page I know of but it probably doesn't provide the information you'd like in a concise manner:

http://www.hdtvprimer.com/

I'll take a stab at answering your question but I'm not sure I'll be successful.

The analog world is pretty easy to understand. A TV picture ranged from perfect studio quality reception to so snowy you could barely make out the picture. Signal to noise ratio was represented in the picture by how much snow and/or ghosts you saw.

8VSB is an analog modulation scheme that has to deal with noise too. What you're really asking about is the ATSC encoding scheme. This consists of data compression, data randomization, and a couple levels of error correction. This data stream is used to modulate the 8VSB signal. In order for this to work and the TV tuner to be able decode a picture and sound, there can only be just so much noise. The maximum level of noise that the system was designed to handle occurs at 15.2 dB signal to noise. At lower SNRs the entire encoding scheme breaks down and the TV cannot produce a picture or sound. The system was designed to produce a perfect picture and sound or none at all.

You almost always hear that since it's digital TV, it either works or it doesn't work, like the digital concept of 1 or 0. That's not the case. It's the ATSC data encoding scheme that causes this "digital like" behavior.

To illustrate this a bit further, I used to receive NOAA low orbiting weather satellites that used BPSK modulation - another digital modulation scheme. This data was very simple, no data compression and no error correcting. It did contain formatting data. When the SNR was too low, some of the bits were received in error due to noise. The resulting pixels assembled from that data would be the wrong brightness values. It looked just like noise. A weak signal could produce a very noisy image, similar to analog TV. To obtain a noise-free image, the SNR needed to be high enough so that noise had no impact on the data decoding. A picture would be produced until the receiver lost carrier phase lock otherwise it just assumed the data was correct.

I'm going to try to explain how noise affects digital modulation, but specifically 8VSB. 8VSB is amplitude modulation and transmits 8 discrete amplitudes. In this system each amplitude represents 3 bits of digital data which are called Symbols. Symbols represent digital 000 - 111. There is never any actual digital 1's and 0's transmitted like you think of it in a computer. It's an analog representation of a digital number. If the SNR is very high, the received amplitude will be the same as the transmitted amplitude. As the SNR goes down, noise begins to randomly alter the received amplitude. There's a small range of amplitudes (think of it as a window) that will still decode the same digital number. Even high SNRs above 20 dB do not produce a perfect received amplitude. As the SNR continues to drop, some symbols will appear out of the correct amplitude range and be decoded as a symbol different from what was transmitted. This is a bit error although it's actually an error of 3 bits. If there are not too many errors, the ATSC system can use its built in error correction to fix these and still produce a perfect picture. At some point there are too many errors to be fixed and the system collapses. An SNR of 15.2 dB is generally the lowest SNR where all the errors can be fixed.

Because of the complexity of the ATSC encoding system, it needs virtually perfect data for it to work. This is the reason why it cannot just fade into the noise like NTSC could.

Multipath acts very much like lowering the SNR. Some of it can be corrected but much of it cannot.

I hope this was helpful, but I don't make any guarantees.

Chuck

Calaveras wrote: Multipath acts very much like lowering the SNR.

Here's an added note to his interesting explanation:

How good your reception is depends on how well your tuner handles multipath. The older receivers were very poor at handling multipath, but over time they have improved immensely. I have an old Sony XBR2 from 2001 that sits in the corner of the office here, but is seldom turned on, because the receiver in it is so bad. Using the same antenna input as my newest receiver, a Panasonic plasma from last year, the old Sony gets less than half the stations as the newer Panasonic. Signals that lock perfectly on the new set, show up as "No Signal" on the old set.

Larry
SF

About 1:30PM today, LWN on 7.3 from Redding and What has been LWN on 10.2 from Sacramento were showing different programming. Has 10.2 changed to something else?

10.2 is still LWN. Different affiliates have different programming.

A possible solution to temperature inversion and multipath issues with Sacramento and Bay Area DTV reception? By late 2012 a new tuner may become commercially available that will greatly improve reception of current OTA HDTV broadcasts and eliminate multipath problems by using multiple receiving antennas, well beyond the 2.5 dB gain possible by ganging two antennas together today:

Could new "SuperTV" reception technology change the Mobile DTV equation?
Dec 1, 2011 4:41 PM, By Phil Kurz
http://broadcastengineering.com/RF/n...-DTV-12012011/

"SuperTV technology using four car antennas makes possible reception of legacy ATSC from a moving vehicle. Although ATSC A/53 was designed for reception of 8-VSB by a TV antenna mounted some 30 feet overhead on a rooftop, SuperTV combines signals from multiple antennas to achieve ground-level reception capable of defeating both Doppler effects and multipath problems that normally would prevent reception of conventional DTV signals in a moving car, said Karamchedu. With two antennas and the MRC technology, the company has seen antenna gain as high as 7dB, and with four it has achieved 12dB of antenna gain, he added.

"With our breakthrough SuperTV technology, for the first time our customers can enhance picture reception quality by simply adding more antennas” said Dr. Lin Yang, Legend Silicon http://www.legendsilicon.com/ co-founder, CTO and inventor of single-carrier MRC diversity technology in a company press release.

"A minimum signal-to-noise ratio of 15.2dB is still required for legacy reception — regardless of the receive antenna configuration," he added."


See:

U.S. Patent Application 20110026579
NOVEL EQUALIZER FOR SINGLE CARRIER TERRESTRIAL DTV RECEIVER
http://www.freepatentsonline.com/20110026579.pdf

U.S. Patent Application 20110080526
MULTIPLE TUNER TERRESTRIAL DTV RECEIVER FOR INDOOR AND MOBILE USERS
http://www.freepatentsonline.com/20110058526.pdf

U.S. Patent Application 20110058600
MULTIPLE TUNER ATSC TERRESTRIAL DTV RECEIVER FOR INDOOR AND MOBILE USERS
http://www.freepatentsonline.com/20110058600.pdf

The Icom 2820 D-Star digital transceiver uses diversity reception with two antennas. Most users don't install the second antenna as the ones who do claim they can't notice a difference. In the areas where DV reception might be improved, it's almost impossible to tell when diversity is helping. Not quite sure how they are combining the signals to measure "gain" in the TV application. I was under the impression that diversity filled in the holes when the first antenna is blocked, yet the signal is reaching the second antenna.

The Icom "diversity" is NOT anything like Legend Silicon's single-carrier MRC diversity technology. All Icom does is switch antennas. MRC diversity technology is a complex mathematical algorithm that eliminates signal noise by comparing, processing, and combining the signals and datastreams separately received by two or more tuners through separate antennas. See:

U.S. Patent Application 20110026579
NOVEL EQUALIZER FOR SINGLE CARRIER TERRESTRIAL DTV RECEIVER
http://www.freepatentsonline.com/20110026579.pdf

IC-2820H Dual Band FM Transceiver
http://www.icomamerica.com/en/produc...h/default.aspx
"Diversity receive capability
If you have two antennas, diversity receive* capability is useful for mobile operation where the received signal strength changes continuously. Within a single band, the radio compares signal strength from each antenna and chooses the better signal to maintain good sound and receive quality."

Also see:
Advantages of Diversity implementation on mobile & portable TV receivers
http://www.dibcom.info/Images/Upload...y4p_B_0805.pdf

For those interested in the details of TV station changes, here is another summary of what's happened in recent weeks in the San Francisco-San Jose, Sacramento-Stockton and Salinas-Monterey markets:

RF 7 K07ZK Monterey - new station has been approved for channel 7 running 300 watts from Mt. Toro
RF 21 KMUV Monterey - analog station on channel 23 has been approved to go digital on channel 21 with 1 kW from Fremont Peak. Station has applied for increase in power to 4.5 kW.
RF 27 KBTV 8 Sacramento - has been granted a change of channel from channel 51 to channel 27
RF 27 KTSF 26 San Francisco - has been granted a power increase to 858 kW
RF 33 KDJT 33 Salinas - station has been approved to go digital with 9.2 kW from Fremont Peak
RF 40 KMMC 40 San Francisco - station has requested power increase from 3.2 to 6 kW. Previous request for increase to 44 kW was rejected.
RF 42 KAXT 1 San Jose/San Francisco - station has been granted a power increase to 1.5 kW

Source: AVS Forum, W9WI monthly updates and FCC website

Larry
SF

Correction:

RF 42 KAXT 1 San Jose/San Francisco - station has been granted a power increase to 15 kW, not 1.5 kW

Larry
SF

KMAX is on the backup transmitter.

I figured they must be on the backup transmitter. I'm getting no signal here in San Francisco when their signal is normally in the 22 to 25 dB range. Same thing happens when KOVR goes on the back up. I think it's actually the same transmitter for both.

Found an interesting thing with my repositioned antennas. I now get 9, 10, 13 and 31 all with pretty decent signals, 17 db and higher, with my CM4228 pointed in the direction of 320 degrees. I must be getting a good bounce off of the hills. Doesn't work for any of the other Walnut Grove stations, though, and it doesn't work for the 10 element VHF/4228 combo located about 12 feet away.

Larry
SF

We use a common backup transmitter and antenna, which operates at 388 KW ERP, for both KOVR and KMAX. As I have said in the past, there is no power directed towards the SF market.

The particular day Chuck mentioned was the day we installed our new studio-to-transmitter ink.

Bob

Here's an interesting article that discusses many of the problems encountered in DTV transmission which are behind unreliable Bay Area and Sacramento DTV reception as it relates to DTV transmission standards. It also demonstrates why Congress and the FCC blew it by prematurely adopting the indequate, legacy ATSC 8-VSB standard in rushing to satisfy the grab for broadcast spectrum by AT&T, Verizon, Sprint, and Obama's Blackberry, forcing the American public and broadcasters to rush out and invest in already outdated and inadequate DTV and HDTV equipment and converter boxes:

Does China Have the Best Digital Television Standard on the Planet?
By Raj Karamchedu, Chief Operating Officer, Legend Silicon
First Published May 2009
http://www.legendsilicon.com/?t=1&m=3&v=,176


TDS-OFDM (Time Domain Synchronous - Orthogonal Frequency Division Multiplexing)



Technical Features
■ Advanced signal processing technology in the time-frequency domain.
■ Guard interval used for multi path protection as well as frame identification, signal acquisition, carrier recovery, symbol timing recovery and channel estimation.
■ Pseudorandom Number (PN) sequence stream is defined in the time domain, and the Discrete Fourier Transform (DFT) data stream is defined in the frequency domain. The two streams are then multiplexed in the time domain, enabling Time Domain Synchronization (TDS).
■ The PN sequence uses spread spectrum technology for fast signal acquisition and tracking capabilities, enabling fast channel changing for digital television.
■ The PN sequence provides signal strength information, which can be used to acquire the strongest signal through receiver adjustment and antenna orientation.

From http://www.legendsilicon.com/?t=1&m=1&v=17

I have several Directv HD Receivers in the house, 3 DVR's and one HD receiver. On all the receivers today and yesterday, when the image is panned or there is motion on the screen there is a considerable amount of smearing and pixelation. I had Directv out to the house today to run two new cables for a new receiver and he could not find anything obvious. The signal strength was strong on several receivers and he also re-cabled the existing connections and added a new cable run and a multiswitch. Please note the problem was there before he did any work.

My outdoor antenna has a much better signal on the local channels so this appears to be a Directv issue. Any ideas what may be going on?
wussery is online now Report Post

Way back in April Smoke_signal made a detailed post about the antenna gain of the Sacramento stations and the reception problems of stations with the highest gain antennas. Since that time I've tried to stay aware of which stations have the largest signal swings and the most dropouts under varying conditions. It's very hard to take actual data on this as just about any station can be affected by conditions, i.e., temperature inversions. But after months you do get an idea of which stations have the most problems. I compiled a list of the stations and the vertical beamwidth of their antennas. I was able to track down all the manufacturer specs from the individual station's FCC applications for their original DTV construction permits. KXTV is the only one I couldn't find and I think this is because they're using their old analog antenna and the original permit is not on-line and the antenna is too old to find in the manufacturer's current catalog. I approximated using a similar current model.

Here's a list from widest beamwidth to narrowest.

Station / Beamwidth-Degrees

KVIE /10.75
KXTV / 4.2
KOVR / 3.0
KSPX / 2.5
KTXL / 2.25
KTFK / 1.75
KMAX-KCRA-KQCA / 1.2

As predicted, my observation is that the KCRA trio has the largest swings in signal strength and the most dropout problems. I have never observed a dropout on KVIE and the signal swings are limited to just a few dB under the most adverse conditions. Much of the time there seems to be little affect if any on it.

All the other stations experience dropouts at times. There's been a couple of bad nights over the last week with the very strong inversions we've had. One night last week the low temperature here was 50 F with a freeze warning in the valley.

KOVR is the best of the UHF stations but it's not immune from dropouts. KSPX is a close second along with KTXL. I don't watch KTFK but it seems to be close to KOVR which is a surprise.

KXTV has a lot of multipath so I get some dropouts on it but it takes really adverse conditions.

I wonder what other people who have less than perfect reception are experiencing? What are the most problematic stations? I especially wonder how KVIE and the KCRA trio compare to here. Is this just a foothill problem and no one else experiences it?

Chuck

Update: Last night (12/27) was classic. There was a dip in conditions in the early evening. KQCA was gone. KCRA was on the cliff. KMAX was barely hanging on. KVIE was completely unaffected. KXTV & KSPX slightly affected. The others somewhere in the middle.

Update 2: There's no figuring out this inversion stuff. Last night (12/29) around 10 pm all the station were nominal SNRs except KVIE which was down 6 dB! Still didn't drop out.

The Walnut Grove stations all vary in strength here in San Francisco, some by as much at 6 or 7 dB. All of the UHF stations seem to vary up and down together and by the same amount. If KOVR drops 3 dB, for example, KCRA, KMAX and KQCA do too.

The two VHF stations don't seem to be affected as much. KVIE usually follows the up and down trend of the UHF stations, but usually not by as much. If they go up 3 dB, KVIE might go up one or two dB. KXTV varies the least. While it will change and does follow the ups and downs of the other stations, the change is usually very small.

KVIE, KXTV and KOVR occasionally drop below the cliff edge, while KMAX and KQCA stay above it. KMAX is the strongest station with a normal signal of 23-24 dB, followed by KQCA at about 21 dB, KOVR at 19, KVIE at 18 and KXTV at 17. I have never received KTFK or KSPX , but their signal pattern doesn't favor the Bay Area. There's a local low power station, KMMC, on channel 40, so there's no chance of receiving KTXL.

KCRA used to be like KMAX and KQCA, but since the KGO translator has come on the air on channel 35, it is below the cliff edge except for times when signals are coming in really well, then it might peak at about 16 dB.

Larry
SF

[quote=Calaveras;21400150]

I wonder what other people who have less than perfect reception are experiencing? What are the most problematic stations? I especially wonder how KVIE and the KCRA trio compare to here. Is this just a foothill problem and no one else experiences it?

KVIE is bullet-proof here. Always on. 20-65 signal.
KXTV has some dropouts. And the antenna must be aimed exactly. The issues are usually because the wind kicked the antenna a few degrees off.
Exact antenna aim ... and antenna pre-amp are the only way those 2 stations work here.

I am in a blocked location ... from Walnut Grove.
Mt. Diablo is the first signal blocker on the path from Walnut Grove.
Then the Alamo, Danville, Castro Valley hills as the second layer of signal blocking rock.
As a result, no UHF tv stations .. from Walnut Grove
The VHF -vs- UHF signal ... clearly shows UHF cannot go over Hills & Mountains
Then add the multipath and its DOA.

Before UHF Digital tv, 13 -KOVR & 3 -KCRA were the signal leaders here.
Talk about a "new" channel line - up. .... (Or station drop)