Sacramento, CA - OTA - Page 314

It is quite possible that the receiver's equalizer sees reflections due to VSWR as no different than multipath and corrects for them.

Yes, I saw that. If anyone wants to read it the pertinent part is on page 4.

http://www.tvantenna.tv/papers/pfactorsv.pdf

The problem with this is that it is talking about mismatch loss and how it increases system noise figure. I have no issue with that and it will only affect very weak signals. The paper doesn't say anything about how VSWR might act like multipath.

The only reference to VSWR acting like multipath is a comment made by holl_ands quoted here at the bottom of the page:

http://forum.tvfool.com/showthread.php?t=2884

It's not quantified though.

We've speculated here that high VSWR can act like multipath degrading the SNR of any signal. So far I've been unable to show that is true.

Chuck

If that's the case then VSWR is no issue. I would think though that improving the VSWR like I did would result in at least a small improvement yet I saw nothing.

My question about equalizers is how many reflections can one cancel out? I was under the impression that it was only one, the strongest one.

My problem here is that I don't just have one reflection, I have hundreds of them. In the analog days if I pointed my antennas to the east where the reflections come from, I had strong signals but I couldn't make out what the picture was because there were so many images. The picture was completely trashed. Main path signals were better but still had ghosts. I never tried to watch analog OTA because the pictures were too ghosty. DTV is actually much better producing a perfect picture in a multipath environment as long as the multipath isn't too bad.

Chuck

"My question about equalizers is how many reflections can one cancel out? I was under the impression that it was only one, the strongest one."

I think the equalizer function is the minimize the error between the received training symbols and the stored replica in the receiver. It doesn't focus on the strongest one. Its ability to minimize errors is affected by the implementation used, some are better than others. The error correction will degrade as the amount of multipath interference increases, so multiple reflections due to high VSWR could tax the equalizer resulting in S/N degradation.

VSWR reflections will be very short in time. For example, 100 feet of mismatched coax will have a reflection time of 300 nanoseconds (assuming 0.66 velocity factor). An 8VSB channel equalizer should have no problem with that. The recommended practice is that the equalizer should handle an echo only 0.5 dB down out to 5 microseconds. See table 5.6 in a_74.

http://www.atsc.org/cms/standards/a_74-2010.pdf

Ron

I agree with you 100%. My point was why waste the limited capability of the equalizer with VSWR reflections if you can reduce the reflections with careful antenna interface designs. The equalizer should be spending all its time and bits on real multipath signals which can cause reception problems. Its similar to the degradation of the X.1 channel when the broadcaster keeps adding more and more subchannels.

Is there a discussion somewhere of how the equalizer works? It must have significant limitations considering the amount of trouble multipath causes for reception.

Chuck

This site has a general discussion of equalizers that may answer some of your questions.

http://forum.tvfool.com/showthread.php?t=101

Thanks! I did see this before but got caught up in the DTS examples. I can see why DTS would likely be of limited use here in the foothills.

This might be all the equalizer explanation we're going to get. I take away from this that equalizers are software algorithms and can adapt to many different multipath situations. But to quote from the article:

Apparently we run into this limitation pretty fast.

Chuck

For what it's worth, I installed a Channel Master 2018 within the last year in Roseville, and it works beautifully. It's only about 12 feet in the air mounted on an eve.

http://www.solidsignal.com/pview.asp?p=CM-2018

Dan

Okay. Ended up not having a lot of time to deal with this, but back into it again.

I was able to find the signal strength meter on the TV. The two corresponding numbers between the TV and Tivo are below.

I currently have a clearstream 4 connected to ~30ft cable into a 4-way splitter and then to the TIVO. With the splitter the TIVO gets a much higher SNR versus connecting the cable directly into the TIVO, which seems awfly strange to me. Could a bad cable cause a splitter to actually increase the signal? I don't think so, which is why I believe the TIVO may have a bad tuner.

Readings:
Tivo 21dB to 31dB - jumps around a lot! And 8VSB
TV solid 33+dB may dip to 31 once in a while but generally bounces around 33 and up. 8 VSB

I have since contacted TIVO and went on a rant with them. They are insisting the problem is on my end, but again, when I look at the signal at the TV vs TIVO it's way off and fluctuates way too much.

Is there anyone else in the Roseville, CA area that has a TIVO setup and not fluctuating wildly?

TIVO is sending a replacement unit, so we will see how that works out.

Randy

Let us know what happens. I'd say it's unlikely the problem is on your end if the TV is stable and the TiVo jumps around. I assume you did run the TiVo off the same splitter port as the TV just for a test.

Chuck

There was a notice in the February newletter of the Worldwide TV-FM-DX Association that there was a new low power station in Sacramento. It's KEFM-LD transmitting on channel 6 with 3 kw from Sutter Buttes. Is it on the air yet? The FCC site shows that the station has a construction permit, but it takes them forever to update the database when the station goes on the air, so I'm looking for your input so that I can update my DTV Station List. (Link below)

Thanks.

Larry
SF

No, it's still analog on channel 6.

Chuck

I received the replacement TIVO unit and it's spot on sitting between 32 and 34 dB. Sending other unit back.

Very happy. Thanks to all the tried to assist!

Randy

Need help regarding my set-up. I am using the Leaf Mohu (regular $40 version) indoor antenna and live in Roseville, CA. I cannot pick up ABC (10.1) or PBS at all. Here is my TV fool report and curious what I am doing wrong since I see them on the list of what I should be able to get with an indoor antenna.

http://www.tvfool.com/modeling/tmp/1dda/408/869ca7a/Radar-All.png

Thanks for any help.

TV stations broadcast on VHF / UHF bands ...... They always have since the beginning of OTA tv
So any indoor antenna must cover VHF & UHF bands (VHF is the rabbit ears and rod elements) UHF is the loop, & bowtie part of the antenna.
The same antenna used in 1950 > is the same antenna you use today.

The Muho leaf is a type of UHF bowtie antenna embedded in thin Credit card type plastic..... So VHF performance cannot be expected.... and is just chance if it happens.
For VHF channels, KVIE on ch 9, and KXTV on ch 10. You must use a VHF antenna.
Don't be fooled by marketing buzzwords and promises. Antennas are simple metal devices designed for a specific radio frequency.
So this is why you are experiencing these issues.

Terk HDTVi/HDTVa is a good indoor antenna that has both rabbit ears for VHF and a very good arrow shaped element for UHF. A very good choice for indoor antennas, sold at Fry's and online vendors. Better choice than those flat panels.

Thanks for the feedback. Is there any thin panel that works for UHF/VHF? I want to hide behind tv or out of sight since this is middle of the room and the terk looks like it would be tough to not be an eye sore. Thanks again.

The Leaf may work for you for KVIE and KXTV. However, VHF signals are prone to fail due to electrical noise. Having the antenna behind the televisions is one of the worst places for it to be located. It doesn't matter if the UHF channels are showing up from the exact same location. The Leaf needs to be moved away from the television. Then turn off all things that use electricity except the television and see if you can get 6 & 10. The correct location/aim/height for your VHF channels can be different from the UHF ones. Good Luck.

There are some that claim they work like this one:

http://www.solidsignal.com/pview.asp?mc=03&p=HDBLADE100&d=Solid-Signal-HDBLADE-Indoor-Digital-Flat-Indoor-TV-Antenna-(HDBLADE)&c=TV%20Antennas%20-%20Indoor%20Only&sku=610370580509

I make no guarantee it'll work for you. Mounting right behind the TV is a bad idea because it may get interference from the TV itself, especially on VHF.

Chuck

Not as much as KVIE's bug-infested, overcompressed picture though!

I've had my antenna right behind my TV and most channels come in well all things considered, even 6 and 10. Whether there's anything to watch on them is a different story (there is a VERY special place in hell for *PBS stations* that use on-screen bugs!)

Which antenna are you using behind your TV?

Here's my input for those looking for a good indoor antenna. I just got the new LEAF antenna for use with my USB DTV receiver on my laptop and I was quite pleased with the results it produces. I receive all of the Sutro, Mt. San Bruno and South Bay stations (except the low power ones), plus 42 from Mt. Diablo and 68 from Novato, so it has a good 35 mile range. I see signals below the cliff edge for some of the low power stations, 22 and 50, but I get nothing from the Walnut Grove stations.

Larry

For what it's worth, I installed a Channel Master 2018 within the last year in Roseville, and it works beautifully. It's only about 12 feet in the air mounted on an eve.

http://www.solidsignal.com/pview.asp?p=CM-2018

I'd be surprised if any indoor antenna works decently from 40 miles out.

Dan

I'm surprised when an indoor antenna works anywhere....

Programming cable or satellite remote to TV (technical)

Slightly off-topic for this forum, but I suspect someone here knows the answer to this: I was troubleshooting a nice Sharp HDTV with an unresponsive Sharp remote. No reaction whatever to any commands from the remote. The batteries were replaced and the IR ports on both the remote and the TV were carefully cleaned, with no help. The button controls on the cabinet worked fine.

I noticed that in trying to program a separate U-verse remote to it, the procedure included the following:

1. Enter one or more of the codes from the list provided with the remote that corresponds with the TV brand, Sharp in this case. I did.
2. The "TV" LED on the remote will respond with one long flash if a code that's not right for that TV is entered, and 3 short flashes when you enter the correct code for that specific TV. I had that exact experience -- a few long flashes, then the 3 short ones on one of the codes.

My question: how does the U-verse remote know that the code was correct for that TV? There's nothing in the remote itself to *receive* anything from the TV -- it only transmits commands. So what would cause the "TV" light on the remote to give me a "yes, that's the right code for this particular set" indication?

I was trying to make another remote work with the set in order to prove the trouble in the original Sharp remote, or in the TV. It ultimately turned out to be the IR receiver in the TV. But I still don't understand how a cable or satellite remote can know when the right code for a specific set has been entered and accepted.

According to what I found on-line for programming the U-verse remote, it will blink 3 times for any correct code associated with the brand of TV you selected. If the remote won't operate the TV it says to try another code from the list. It would appear that it doesn't know.

http://www.att.com/esupport/article.jsp?sid=KB407920&cv=803&title=Program%20your%20U-verse%20remote%20via%20the%20TV%20setup%20tool#fbid=5ACLgjKo_ql

I assume that since your TV IR receiver was bad you were not able to verify that the remote controlled the TV.

Chuck

I've got the $10 RCA antenna from Wal-Mart. I had another kind before, and 6, 10 and 19 were usually the hardest stations to get. This one gets them in most of the time, was actually able to watch the news on channel 10 a few days ago with no dropouts. Still can't get low-power channel 49.

All of the codes tried were for the correct brand, Sharp. One and only one of them gave the "right code for this specific model" response (3 blinks). I'm struggling to fathom how that's possible -- what tells the remote that I've entered the correct code, out of many Sharp codes, for that particular Sharp model?

And yes, I verified that the Sharp remote was okay by trying it on another Sharp TV, which worked fine.

--Ron