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622 OTA Overload/Multipath Problem


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31 replies to this topic

#21 OFFLINE   TechniKal

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Posted 20 March 2007 - 10:54 AM

The thing I'm most curious about is why does it impact the 622 more than other tuners, and why does it impact FOX channels more than other OTA networks?

I can't imagine Dish has a proprietary tuner in the box. Near as I can tell, it's the same Broadcom 'tuner on a chip' solution tons of other OEMs are using - but for some reason it's a problem in the 622.

And why is it usually FOX that's having an issue? Do most FOX stations use the same broadcasting hardware?

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#22 OFFLINE   boylehome

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Posted 20 March 2007 - 12:04 PM

The thing I'm most curious about is why does it impact the 622 more than other tuners, and why does it impact FOX channels more than other OTA networks?

I can't imagine Dish has a proprietary tuner in the box. Near as I can tell, it's the same Broadcom 'tuner on a chip' solution tons of other OEMs are using - but for some reason it's a problem in the 622.

And why is it usually FOX that's having an issue? Do most FOX stations use the same broadcasting hardware?


When will Axcera get their exciter/modulator problem fixed? I think that the problems are closely related to their product. Here, the problem just keeps getting worse. Last weeks attempt to fix has now made it so the attenuation doesn't work very well. I know that other stations state that they don't have the same equipment, I wonder if they are being truthful?

It would be nice if E* could get the ATSC tuners for the Vip 622/211 to work like other tuners that work well with the problem signal.

#23 OFFLINE   mraub

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Posted 20 March 2007 - 12:43 PM

By the way, the staition I first posted about is a CBS affiliate, not Fox.

MIKE

#24 OFFLINE   Mr.72

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Posted 20 March 2007 - 12:45 PM

OK, has anyone actually opened up the 622 to see which chip/chipset is doing the ATSC tuner/receiver role?

I suspect maybe it's the BCM97395, in which case this thing requires tuner chips (like Broadcom BCM3418 or maybe something else) as well as the first device in the chain, the "LNA" aka "Low Noise Amplifier". You can see the basic topology of this particular Broadcom chip here:

http://www.ortodoxis...a48wpowr1ky.pdf

So as in any transmission technology, be it analog, digital or whatever, you have to have an amplifier. This amplifier is not likely integrated into the Broadcom chip, but Broadcom may want to sell you one. However, that amplifier has to be accompanied by a host of other components (even if it is a Broadcom amplifier but you kow there are a zillion op amps on the market that would do this job) including capacitors and resistors, PCB layout, power supply, decoupling, etc. Analog amplifier design, especially at RF frequencies, is far more art than it is science. If there is distortion causing this problem, this is where it is.

Speaking of that, a host of other design problems could be causing this including oscillation, build problem (like substitute, say, a .1uF capacitor in place of a 100pf capacitor which is not detectable with computerized QC board analysis tools), power supply switching noise, clock leakage, localized RFI inside the enclosure coupled from adjacent circuitry, ringing, etc. So it may very well not be distortion, but since there are problems with multiple frequencies (different channels around the country) it makes me think it may not be one of these issues since they would be frequency-specific. Also, it's not just Fox, although it is commonly Fox. I wonder if the 720p signal may be exacerbating or exposing the problem. I really don't know anything about the data encoding of HDTV.

#25 OFFLINE   Todd H

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Posted 21 March 2007 - 05:34 AM

I have trouble with my 622 and OTA as well. When I use the tuner in my television, I can pick up a couple of stations. But when I use the tuner in my 622, scan for locals, and add them then I have problems. I can turn it to one of the OTA stations on the 622 and get a black screen. About 10 seconds later my 622 locks up and needs a reboot. Even after the reboot if I turn it to one of my OTA stations it locks up.

#26 OFFLINE   Mike D-CO5

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Posted 21 March 2007 - 06:27 AM

Anytime I go into the locals menu and add or rescan or anything related to the locals menu, I get a black screen on any ota station and then I have to reboot or it will reboot itself. It is definately software related and it needs to be fixed. THis has happened everytime I go into this menu for over a year now.

#27 OFFLINE   dak0ta11

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Posted 21 March 2007 - 06:45 AM

I am experiencing the same issue. I went in and re-scanned my locals yesterday. Box slowly died, then rebooted. It only happens when I "play" around with my ota channels.

#28 OFFLINE   Todd H

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Posted 21 March 2007 - 07:35 AM

Hope E* is listening because it definitely sounds like some kind of bug.

#29 OFFLINE   David_Levin

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Posted 21 March 2007 - 07:49 AM

I have some long cable runs and splits, so was using a powered splitter from Radio Shack. It made the signal worse.

I then tried an amplifier with a switchable FM Trap. One channel (UHF 19) woud not lock unless the FM trap was enabled. With this configuration the amp brought up the signal strength 5-10 points.
Bye Bye 921
Now playing with 2x 622s.

#30 OFFLINE   RandallA

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Posted 21 March 2007 - 08:10 AM

I have some long cable runs and splits, so was using a powered splitter from Radio Shack. It made the signal worse.

I then tried an amplifier with a switchable FM Trap. One channel (UHF 19) woud not lock unless the FM trap was enabled. With this configuration the amp brought up the signal strength 5-10 points.


I deleted it a couple of sub-channels and a few seconds later all I got was a black screen. I had to reboot the receiver to get the picture back. Definitely something wrong with the software.

#31 OFFLINE   ChuckA

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Posted 21 March 2007 - 08:34 AM

This was reported months ago. E* is aware the OTA screen can cause a re-boot. I expect it is already addressed in the up comming software release. But, as we hear so often, we'll just have to wait and see.
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#32 OFFLINE   Mr.72

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Posted 21 March 2007 - 08:53 AM

I would be surprised of the OTA-channel-scan-crash is related to the reception problems we are talking about here.

One thing is very clear: OTA is not the priority feature of the 622. When you buy a TV with an ATSC tuner in it, OTA is indeed the priority.

It's kind of like people saying, hey when I try to take that corner at 60mph in my mini-van, it slides off the road and crashes. But when I try it with my Ferrari, it holds on just fine. What's wrong with the mini-van?




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