Sacramento, CA - OTA - Page 313

Crazy TV Conditions Tonight

Ducting to Salinas is so strong here right now that KQET on Fremont Peak which is co-channel with KOVR is preventing KOVR from being decoded even with a pair of 91XGs pointed to Walnut Grove! That's rather amazing since KQET only has a couple KW ERP in this direction from 115 miles away. So I've given up and am watching Salinas tonight.

Chuck

Chuck... You seem to have a really good shot at the stations from Fremont Peak and Mt. Toro and with ducting you get some amazing reception for the distance!

As I noted on the SF OTA thread, conditions here in San Francisco, have generally been rather poor lately. Only KMAX 31 and KQCA 58 have been coming in solid here from Walnut Grove, and I haven't seen the two VHF channels from there for several days. They've been down in the 13-14 dB SNR range.

KEMO 50 from Mt. St. Helena, on the other hand, has been booming in here with a much better than average signal. They've been holding at 28 to 29 dB lately. How to KEMO and KION, both RF 32, compare in strength up there?

Larry
SF

KEMO is fairly consistent running about in the 20 - 25 dB range most of the time. KION has huge swings in signal from not decodable to 32 dB. When it's strong it over powers KEMO and I can't receive KEMO at all. When it's weak KEMO causes it problems.

I saw something new today.... KBFK Bakersfield on RF 33 for a very brief time. After some research I discovered that I actually saw KBFK virtual 58.2 being rebroadcast on KBAK Bakersfield on RF 33.2. That's 219 miles. I think that's the first digital station I've seen from Bakersfield. I have seen analog stations before the transition from Bakersfield. The transmitter site down there is over 7000'.

Chuck

Edit: Captured KBAK/KBFX this morning.


Edited by Calaveras - 12/8/12 at 7:48am

Nice catch, Chuck!

Larry
SF

Monday 12-10 was a good day here. All the Chico -Redding stations were in the 90s here and even KRCR -7 was coming in solid for a time with only a UHF antenna.

Amazing that you saw KBAK. Their antenna is well to the east of the valley and all the peaks in between would block a direct signal. Must have been an inversion that hit you just right.

I can work a two meter repeater north of Bakersfield, but it's on the west side of the valley and has a direct signal path. I don't hear the degree of path fluctuation on signals to the south that I get on the Chico signals. Chico is near 100% when the ducting is in and gone when it's not.

KSBW is the only Salinas station I sometimes receive and I have never seen it over 65. I used to get analog channel 2 from Salinas but haven't seen it recently. Is it still on?

The most consistent Bay Area station here is KOFY-20, about 95% of the time. It beats out KCRA-3 for consistent viewing. I think I need an antenna on a portable pole to walk around and find the best antenna spots. I receive different channels on two different antennas mounted fifty feet apart at about the same height probably due to the tall pine trees here.

Ernie
Daffodil Hill, Amador County

Yes, KOTR is still on but they changed their antenna direction and lowered their power awhile back so they're much weaker.

Chuck

"RetroTV" has moved from KCNS 38.5 San Francisco to KTNC 42.4 Concord, which transmits from atop Mt. Diablo, so it should now be available to everyone in the Sacramento/Stockton/Modesto market. (It replaces the color bars they've been transmitting for several months on 42.4.)

Larry
SF

Signal strength indicator on HDTV models?

I'm getting close to my next TV purchase. Among those I've obtained or worked on in the past, there are a variety of S-meters. Some have an almost useless bar graph indicator, like on your cell phone, while at the other end you have 0-100 digital meters that allow fine tuning of your antenna.

I only want a set with the latter, or some variation of that quality. Are they found in particular brands? I know of a 6-year old Sharp that has it. Do all Sharps? Others? Which ones have only the rough bar graph, or anything else that doesn't really cut it?

Tks,
--Ron

I don't know about every TV but I've never heard of any that have only have a real signal strength meter. All that I've heard of or have personal experience with have a signal quality meter. I know someone with a Sharp and it too has a signal quality meter.

Every Sony I know of has a diagnostic screen that has an AGC reading. AGC is a real signal strength meter although it reads in reverse, i.e. the lower the number the stronger the signal. The AGC gives a reading as long as it can phase lock on the pilot carrier which appears to be down to 13 dB SNR or so. That gives a signal strength reading on stations that are slightly too weak to decode. With my setup, the strongest signals I receive give an AGC reading of 29 and weakest decodable signals around 65. Some very weak signals read as high as 72. I have verified against my spectrum analyzer that you can peak your antenna with the AGC meter. It can read a difference of about 1 dB.

If you were to choose a Sony you should be able to ask on one of the owner's threads about the diagnostic screen. The diagnostic screen on my Sony reads RF channel, Frequency, Uncorrected Errors, SNR, AGC and a few other things.

The only thing I wish Sony had included was a signal quality reading on the main screen Display info so you could have that by pushing only one button. The diagnostic screen is buried down in the menu system.

Chuck

It has been quite a while since I have posted here. First, I should thank everyone for their help. We've been running strong with the antenna and are exceedingly happy. The late summer months were a bit of a bear at times, but we haven't seen any issues since... well, until today. I was trying to watch the Today show on channel 3.1 and the entire channel (along with 58.1) went out for about 20 minutes or so. As I type, things are still a little spotty. Were there tower issues today?

Thanks,
Roy

P.S. I built an awesome HTPC that is working great!!! It's our Blu-Ray, TV tuner, DVR, and Roku all in one.

Probably inversion issues which are becoming very strong as of last night. There's not much you can do about it. This morning it was 43 degrees at my house at 2500' while some valley locations were seeing upper 20's. This is going to continue for awhile. We haven't had a lot of this so far this winter season.

I'm seeing very good signals from Walnut Grove at the present time. Salinas is also roaring in with some signals as much as 20 dB above average.

Chuck
Edited by Calaveras - 1/16/13 at 3:15pm

Thanks.

If this has been common of late, then I am lucky. I haven't seen it until today. Good!!!

Seeing you were seeing some activity yesterday, I thought I'd take a look today.

As I've reported in the past, if the signals from the South Bay (Mt. Allison and Monument Peak) are up, the signals from Walnut Grove are usually down. That's the story today. KAXT 1 is normally about 17-18 dB SNR; today they're 23.76 dB. KMAX 31 is normally 24-25 dB; today it's 18.62 dB... and the ONLY signal I'm receiving from Walnut Grove. Channels 6, 10, 13 and 58 are all below the cliff edge today.

KEMO 50, normally about 28 dB is down to 23 dB today.

What's it look like up your way today, Chuck?

Larry
SF

Most of what I've been seeing here has been negative, some dropouts of the Walnut Grove stations, and little enhancement of anything else. Salinas is good this morning but not exceptional. We certainly are having inversions since it was in the low 50's all night while the valley dropped to the upper 20's/low 30's.

Chuck

Re: Signal Strengh indicators in HDTVs

Chuck, thanks for that. Roger the AGC reading relating directly to signal strength. As for "strength" vs. "quality," aren't they functionally the same with DTV? You gotta have sufficient strength to form a watchable picture (quality). Okay, that's semantics....

Back to the TVs. I checked 3 that I could easily get to, and the Sharp has an easy-to-use 0-100 indicator that reacts in real time--moving the antenna changes the reading. My 2007-vintage Samsung has a really poor bar graph that actually appears to have only 3 states: GOOD, FAIR, or BAD. Worthless for fine-tuning an antenna. My 3-year old Vizio in the office gives a numeric 0-100 indication, but you have to drill deep through the menu to find it.

--Ron

Not at all.

The theoretical dynamic range of a digital signal might approach 80 dB differential between the weakest and the strongest that the tuner can decode. If the "quality" of the signal is good enough regardless of the power level, the decoded digital information is the same and the resulting picture is identical.

Signal Strength and Signal Quality are different but interrelated things. Signal Strength is just that, the absolute level of the signal, unaffected by noise or mutipath. Signal Quality is identical to Signal-to-Noise Ratio and is dependent on signal strength, noise and multipath. With a signal strength around -65 dBm the DTV signal can achieve better than 30 dB SNR (100% on most SQ meters), essentially as good as it can get. But that's where the relationship ends. Noise/interference and multipath (which acts like both noise and interference) lower the SNR on even a much stronger signal.

All those 0-100 meters are signal quality meters. In most cases the SNR and the Signal Strength will peak in the same antenna direction. In that situation the signal quality meter is fine. The problem people run into all the time are signals that won't decode. When that happens the signal quality meter is useless. Most people assume that if the signal won't decode it's because it is too weak but in many cases with poor antennas the problem is really multipath. A signal strength meter would indicate if the signal is strong enough even when it won't decode.

A Signal Strength meter and a Signal Quality meter go hand in hand to troubleshoot reception issues.

Chuck

Hello all.

I live in Roseville and decided to cut the cord. I purchased a Tivo Premium 4 with a ClearStream 4 from Antenna's direct. I ended up calling out someone to help with the setup, but I still have problems. From what I can tell I should be getting close to 100% based on what I have read about others in the Roseville area.

When I check the signal strength through the Tivo, especially with 3.1 and 40.1 it's a really low signal. On 40.1 it would fluctuate from 60+ down to 30. I had a preamp installed and removed it improving the signal, but still would get pixelation.

When I connected a 4 way splitter the signals went up to around 80%, but 40.1 is still only around 60 to 70, which is much better, but I fear it may start dropping out.

From the splitter I connect directly to the TV and through the Tivo, so when I see problems on Tivo I switch to directly to TV and the TV never has a problem.

Do I have something configured incorrectly, or could I have a problem with the Tivo unit? If it could be a problem with the Tivo unit how can I convince Tivo support that the unit is the problem?

Frustrating.

Thanks.

Randy
Randy@sacandbeyond.com

There are numerous reports that the series 4 OTA tuner is not as good as the series 3. It appears that the signal quality is down about 3-4 dB from one report I read. Since I've been reading about this for over a year, I'm sure TiVo support knows about it.

If you removed a preamp and the signal quality went up, then the tuner is probably being overloaded by the preamp. Does this happen with both the TiVo and the TV tuner?

When you say that the signal quality went up when adding a 4-way splitter, was this when you had the preamp connected or disconnected? Unless your signals are very weak (unlikely), there should be no change in signal quality when adding a splitter.

Chuck

I don't know if it's happening with the TV since I don't have a way of measuring the signal like on the Tivo. The preamp is not installed with the 4-way splitter and the signals are quite high when compared to connecting straight to the device.

I really want to understand why the signal is going up with the splitter versus a straight connection. I'm trying to get the best possible signal possible, but I'm struggling since cause and effect seems to not be what it should be.

The only thing I haven't done is ground the antenna. Do you think that might make a difference?

Thanks for responding, I appreciate it.

Randy

I don't know what's going on with the TiVo since I don't have one and what I've read isn't all that helpful. If the TiVo has only one meter then it's a Signal Quality meter and not a Signal Strength meter. A higher reading simply means the signal quality (signal-to-noise ratio) is higher, not that the signal is actually stronger. I can't really say why this is happening when you add a 4 way splitter.

Doesn't your TV have a Signal Quality meter? Almost every one does. Does the signal quality on the TV go up too when you add the splitter?

Chuck

Isn't the Clearstream4 UHF only?

I know that's not entirely pertinent to the problem.

Since the channels he's having trouble with are UHF, it probably isn't an issue. The C4 is not blind to VHF, it's just severely nearsighted.

Mose likely, if the problem is restricted to only to stations, he's getting multi-path and a relocation of the antenna is probably in order.


This can happen with multi-path. The signal power of the reflected signal's out of phase power is reduced at the tuner and decodability is improved.

I really don't think this is true. I've never heard of it and never personally experienced it. If it was possible then there would be all kinds of schemes available to try to reduce multipath. If you could cite some examples of how to purposely do this I have plenty of stations with multipath to try it on.

Chuck

Here is my 2 cents. If the tuner impedance does not match the cable impedance then there is reflections back to the antenna. If the antenna/balun impedance does not match the cable impedance then there is another reflection back to the tuner, etc. These multi-reflections may stress the equalizer in the receiver resulting in a lower signal quality. However, having a splitter acts like a x dB pad reducing the magnitude of the reflections on each pass. Less stress on the equalizer results in a higher quality signal.

I tried to read up on this a little and the opinion out there is that a high SWR can lower the SNR as the result of reflections on the coax but it's hard to get it quantified.

Here's a little test I just ran. I connected my TV to the antenna with the coax center conductor only, no shield connection. I picked a strong UHF signal and a strong VHF signal because all signals are highly attenuated when I do this. There was no decrease in SNR due to the shield being disconnected. Certainly this would make the SWR very bad and reflections high.

Sometimes it's helpful to think of extreme situations when I can't quantify the effects. My portable DTV has a very short antenna that must have a very high SWR. When I had this TV in a good location its signal quality meter showed high readings on the Sacramento stations using just the whip. Also we know a lot of people are using UHF antennas to receive VHF stations successfully. If high antenna SWR was a significant factor in SNR then these antennas wouldn't be able to receive any VHF stations.

At this point I cannot reconcile the theory I'm reading with real world results. The OP was having trouble with UHF stations, not VHF stations and his antenna is a UHF only antenna. It seems pretty unlikely that SWR would be causing a problem on UHF and not on VHF.

Chuck

I am preparing a move from my home in Rancho Cordova to area near I-80 and Greenback the home i am buying appears to have antenna restrictions and although that sucks that is OK, however I noticed I have a large smokestack for my fireplace that I will never use conventionally (if I do it will be electric) what kind of antenna could i make to top the stack that will disguise, shield and give me omnidirectional reception for tv and radio thanks BUD

For the most part the FCC has preempted CC&Rs for TV antennas and small satellite dishes. You can put up on your own property what is required for OTA reception with some limitations.

http://www.fcc.gov/guides/over-air-reception-devices-rule

Chuck

A little more on VSWR....

I spent half the morning measuring VSWR on my own setup. I discovered that it is not very good. The diplexer, filter, power inserter and several jumper cables all conspire to push the VSWR up to 3:1 at some frequencies. The transmission cable itself is quite good measuring around 1.2:1. As a test I bypassed as many of the offending components as possible and compared some SNRs that the TV gave. I tried weak signals on VHF and UHF barely above the cliff and stronger signals with SNRs limited by multipath. In all cases the SNRs were exactly the same reading to 0.1 dB.

Despite the discussions about this that I read, this seems to be a complete non-issue. I don't know why the theory isn't translating to reality but if measured data disagrees with theory then there's something wrong with the theory.

I found a few papers detailing the affects of VSWR on transmitted SNR with very nice graphs showing a typical broadcast station. I could find no corresponding data on the receive end. There were convincing arguments for the existence of VSWR effects on SNR but no numbers. My guess is that the effects are too small to be noticed in the typical consumer setup.

At this point I wouldn't tell anyone to worry about VSWR. It's an unnecessary confusion factor for people who already can't figure out why they have reception problems. Almost no one can measure it and antenna specs don't mention it. The only place I've even seen it for TV antennas is from computer modeling and then only as Mismatch Loss which is derived from VSWR.

Chuck

Thanks for taking the time to run experiments.

A paper by Charles W. Rhodes does discuss VSWR effects on received SNR.

"Planning Factors for Fixed and Portable DTTV Reception"

He ran experiments at different VSWR levels and he saw SNR degradation as the VSWR increased. He made the following recommendation:

"What should be the effective noise figure for service planning? The FCC has recommended 7 dB for the UHF band and 10 dB for the VHF band. These values do not include the effect of the impedance mismatch between the antenna and the front-end of the receiver. Given our previous analysis and current experiments, we believe that effective noise figure for single-conversion receivers, including the VSWR effect of practical antennas, be raised from 7 dB to12 dB for all bands."