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Interesting failure mode


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26 replies to this topic

#1 OFFLINE   TomCat

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Posted 19 November 2013 - 12:23 AM

I admit up front I have posted regarding this before, but thanks to the gurus here and some testing, I now have further info. I also posted that in the wrong place.

 

Briefly, I have a non-SWM SL5 and 4 HR2x's.

 

The oldest HR20 intermittently loses tuner 1 completely, but only on 103s. A reboot brings it back for a day, a week, whatever. The other tuner does not lose connection, and no other sat loses connection. I have watched shows recorded on this DVR and some of them show brief severe pixellation. Others do not. Signal levels are good; I have 100 on the main spot beam xponder. Except when I have zero on tuner 1. I get a lot of blank recordings, and probably because of this issue. Most of what I record comes from the spot beams on 103s (go figure).

 

I have replaced both BB converters, and if I swap feeds at the back of the DVR, Tuner 1 is still the one missing. The other 3 DVRs never have this issue.

 

Originally I thought since it affected only one sat it was the switch in the LNBF. I planned to replace it with SWM, but now I fear that the problem is really in the DVR, and that going to SWM might even aggravate the problem, so I am holding off on that changeover.

 

A "tuner" is really a number of things, including a heterodyne converter front end to get the signal from L-band to IF, another converter to demodulate it to baseband, a router (the fact that I can swap input cables and tuner 1 is still the one with the issue implies that there is a router that enables either RF input to be routed to either tuner), and demux. The particular symptoms seem to point to the problem being either at the router point or downstream of that. And of course there are two independent tuner paths up to that point (four if you count OTA), and two independent routers/demuxes, for a grand total of two complete tuner paths.

 

Here is another clue; the OTA signal also disappears on tuner 1 on occasion, and it appears that if I lose tuner 1 on sat, I also lose it on OTA. Since that is a separate demod path but is probably routed into the same path just before demux that the sat signals are routed into, that implies that the problem is downstream of demodulation, in the tuner 1 path.

 

But I need the experts' take on this.

 

I also need to hear what you think about whether moving to SWM would improve the issue, make it worse, or probably not affect it one way or another (I sort of think the last choice is most likely).

 

Also, where is the info that marries the database to the HDD? My guess is that it would be on the board with the tuners, but it it is instead on the board that has the power supply and microprossessor, I can get my hands on a spare actually brand-new tuner board, and I could then theoretically swap out the tuner board, keep the PS/microprocessor board, fix this problem, and still be able to play back existing recordings. Probably wishful thinking. Does anyone know?

 

BTW, this is a Pace DVR. Please, no warnings about popping the hood; that boat sailed a long time ago.

 

TIA.


Edited by TomCat, 19 November 2013 - 12:38 AM.

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#2 OFFLINE   inkahauts

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Posted 19 November 2013 - 12:34 AM

Well it might help I go swim but not sure.

The over the air not working is after you have already had a sat channel not work right? I think yet get locked to no signal and your stuck in that mode till you get it back via sat channel but not positive.

Have you noticed any pattern of which channels lose signal? Or is it randomly and any?

Also have you reloaded the software? I didn't see your other thread.

#3 OFFLINE   jimmie57

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Posted 19 November 2013 - 08:06 AM

Based strictly on what you wrote, It sounds like the problem is always on the same receiver and the same tuner. I would replace it because it has a bad tuner.


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#4 OFFLINE   Stuart Sweet

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Posted 19 November 2013 - 08:26 AM

Here's a nice fence-straddler for you: I think it is the tuner and I also think moving to SWM might fix it. It really depends on the nature of the failure. The way SWM is tuned is so different from the way that L-Band is tuned, it's like you have two separate receivers almost.

I personally recommend going to SWM for anyone who has multiple receivers. We're past the "if it ain't broke" phase, SWM isn't just the future at this point. SWM is the present and to an extent the past. It's time to get off legacy wiring. If that doesn't solve your problem, then I would say that you should also swap the receiver.

Unless you are on the protection plan, you're talking about a new 2-year commitment anyway, so why not call DIRECTV and see what they'll offer you for a SWM upgrade and a new receiver. That is, unless you'd rather do the work yourself, which I respect.
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#5 OFFLINE   NR4P

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Posted 19 November 2013 - 08:28 AM

To Stuart's point, you might as well go SWM and then upgrade your equipment since the new equipment is SWM only anyway.

 

I used to have 3 HR20s.  Great boxes during their time.   Now have Genie and HR24 with AM21's.

The HR20's are 2006 vintage.  Time to move on.   I wasn't happy to give up my last HR20 but looking back, very glad I did.  They look old and are big.

 

And the AM21's have better OTA tuners.  Much better multipath rejection.

 

I know you want to nail the problem but going forward the HR20's are just going to be more headache than they are worth.

 

As SS points out, investigate upgrading and then decide.



#6 OFFLINE   JosephB

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Posted 19 November 2013 - 09:17 AM

 (the fact that I can swap input cables and tuner 1 is still the one with the issue implies that there is a router that enables either RF input to be routed to either tuner),

 

That's not working how you think it's working. When you swap the cables, the second input isn't suddenly being routed to tuner 1, it's just that either coax can be selected to carry any satellite/polarization combo. It doesn't send different RF inputs to different tuners. The fact that you can swap them around and you still get the same behavior on the same tuner on the same box only implies, however, that the problem is in the receiver and not in your dish or switch.

 

Like everyone else has suggested, I'd upgrade to a SWM system first and then if you still have problems, replace that receiver.



#7 OFFLINE   carl6

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Posted 19 November 2013 - 01:44 PM

I do agree the problem is in that specific tuner in that specific DVR. You've proven that with the troubleshooting steps you have taken.  SWM may or may not make a difference, but I don't think it would hurt to try.

 

As to swapping out the main board inside the unit, the encryption is a combination of the access card and other components. I have replaced power supplies to recover boxes, but have never tried replacing other boards. If you have the spare parts, and want to give it a try, you have nothing to lose (other than the time and effort to try it).  If you do, let us know what happens.



#8 OFFLINE   TomCat

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Posted 19 November 2013 - 03:22 PM

... When you swap the cables, the second input isn't suddenly being routed to tuner 1, it's just that either coax can be selected to carry any satellite/polarization combo. It doesn't send different RF inputs to different tuners...

 

If I have one cable connected to the first input it shows no connection on tuner 1 and 100% on tuner 2. If I have just the other cable connected it does the same thing. If I connect either cable to the second input it does the same thing.

 

All that implies is that both polarities of 103s are getting to the DVR through either cable. It does send different RF inputs to different tuners if you select something on a different satellite, and even if you select the same transponder on the same sat (which is what I am doing here) it is an identical feed, yet a duplicate feed, It is the same signal but a truly physically different path up to that point. The entire idea of being able to record any two signals from 3 or 5 satellites implies that different RF is sent to different inputs.

 

SWM is different. All 3 sats are sent in 3 separate freq bands down one wire, and each tuner selects what is desired by converting to IF using different LO frequencies and switching polarities. On a DVR futured for SWM but getting a conventional L-band input, that is what the BB converter is for, to move the single 950-1450 L-band signal up to the higher band or down to the lower band, mimicking the behavior of a SWM input.

 

In my case (conventional L-band) the fact that either input can show 100% on just tuner 2 on the same sat indicates that there is a routing capability here, which switches between the two inputs.


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#9 OFFLINE   JosephB

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Posted 19 November 2013 - 04:57 PM

 

 

SWM is different. All 3 sats are sent in 3 separate freq bands down one wire,

 

That's actually not how SWM works. SWM works by selecting a certain transponder and putting it into one of eight frequency bands.

 

To send all three satellites you'd actually need 6 frequency bands (each polarity for each satellite). 



#10 OFFLINE   TomCat

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Posted 19 November 2013 - 08:47 PM

OK, you have spurred me to research this. I thought there was no frequency-agile conversion at the LNBF, but it turns out that there is. Thank you for that clarification.

 

So what I get out of this is that the failure mode I am seeing might be related to the signals sent to the BB converter that tells it to either pass frequency direct or convert. We know the BB converter is good, but it might be getting intermittently-bad signals from the tuner, and passing 103s instead of upconverting it, while the other tuner is operating properly.

 

This raises this question: does the signal sent to the BB converter and to the conventional LNBF differ greatly from the SWM control signal?

 

If so, a change to SWM might fix this. If not, a change to SWM might make the failure permanent or increase the odds of losing recordings on either tuner on that DVR (when on 103s). Not really knowing, my guess would be that it would fix it.

 

I have not been able to Google a definitive explanation of exactly how SWM works frequency-wise or control-wise, only that it creates the 8 100 MHz private bands you spoke of, and assigns that to a particular receiver through that control signal, which I'm guessing must be much different than how the conventional system controls a conventional LNBF.

 

One thing I have not determined is whether I lose recordings with just one program scheduled, but I think I do.

 

I built and operated numerous TVRO sites for cable TV, and operated a satellite uplink truck for over a decade for a news organization, but SWM is somewhat different technology than the pro stuff.


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#11 OFFLINE   peds48

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Posted 19 November 2013 - 09:07 PM

That's actually not how SWM works. SWM works by selecting a certain transponder and putting it into one of eight frequency bands.

 

To send all three satellites you'd actually need 6 frequency bands (each polarity for each satellite). 

Actually from some DirecTV "official" training videos, just the specific channel selected is send down the cable to be decrypted and decoded by the receiver.


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#12 OFFLINE   inkahauts

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Posted 19 November 2013 - 11:18 PM

Actually from some DirecTV "official" training videos, just the specific channel selected is send down the cable to be decrypted and decoded by the receiver.

 

Well that's hilarious, because it sends down a transponder, not a channel.  To funny they don't have that right...



#13 OFFLINE   inkahauts

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Posted 19 November 2013 - 11:19 PM

OK, you have spurred me to research this. I thought there was no frequency-agile conversion at the LNBF, but it turns out that there is. Thank you for that clarification.

 

So what I get out of this is that the failure mode I am seeing might be related to the signals sent to the BB converter that tells it to either pass frequency direct or convert. We know the BB converter is good, but it might be getting intermittently-bad signals from the tuner, and passing 103s instead of upconverting it, while the other tuner is operating properly.

 

This raises this question: does the signal sent to the BB converter and to the conventional LNBF differ greatly from the SWM control signal?

 

If so, a change to SWM might fix this. If not, a change to SWM might make the failure permanent or increase the odds of losing recordings on either tuner on that DVR (when on 103s). Not really knowing, my guess would be that it would fix it.

 

I have not been able to Google a definitive explanation of exactly how SWM works frequency-wise or control-wise, only that it creates the 8 100 MHz private bands you spoke of, and assigns that to a particular receiver through that control signal, which I'm guessing must be much different than how the conventional system controls a conventional LNBF.

 

One thing I have not determined is whether I lose recordings with just one program scheduled, but I think I do.

 

I built and operated numerous TVRO sites for cable TV, and operated a satellite uplink truck for over a decade for a news organization, but SWM is somewhat different technology than the pro stuff.

 

What do you mean by lose recordings or just scheduled?  



#14 OFFLINE   slice1900

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Posted 19 November 2013 - 11:41 PM

Well that's hilarious, because it sends down a transponder, not a channel.  To funny they don't have that right...

 

 

All installers really need to know is that when a SWM receiver tunes a channel, the channel is delivered in the SWM "channel" assigned to it. It's probably not them "not having it right" but rather trying to simplify things and avoid creating confusion by providing unnecessary detail that isn't required for them to do their jobs.


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#15 OFFLINE   inkahauts

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Posted 20 November 2013 - 12:35 AM

All installers really need to know is that when a SWM receiver tunes a channel, the channel is delivered in the SWM "channel" assigned to it. It's probably not them "not having it right" but rather trying to simplify things and avoid creating confusion by providing unnecessary detail that isn't required for them to do their jobs.

Oh I know, but still, its funny they tell he techs the wrong thing.  I think that is the wrong way to do it myself, but hey, the trained may not even know he wrote it wrong either.



#16 OFFLINE   JosephB

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Posted 20 November 2013 - 07:44 AM

OK, you have spurred me to research this. I thought there was no frequency-agile conversion at the LNBF, but it turns out that there is. Thank you for that clarification.

 

So what I get out of this is that the failure mode I am seeing might be related to the signals sent to the BB converter that tells it to either pass frequency direct or convert. We know the BB converter is good, but it might be getting intermittently-bad signals from the tuner, and passing 103s instead of upconverting it, while the other tuner is operating properly.

 

This raises this question: does the signal sent to the BB converter and to the conventional LNBF differ greatly from the SWM control signal?

 

If so, a change to SWM might fix this. If not, a change to SWM might make the failure permanent or increase the odds of losing recordings on either tuner on that DVR (when on 103s). Not really knowing, my guess would be that it would fix it.

 

I have not been able to Google a definitive explanation of exactly how SWM works frequency-wise or control-wise, only that it creates the 8 100 MHz private bands you spoke of, and assigns that to a particular receiver through that control signal, which I'm guessing must be much different than how the conventional system controls a conventional LNBF.

 

One thing I have not determined is whether I lose recordings with just one program scheduled, but I think I do.

 

I built and operated numerous TVRO sites for cable TV, and operated a satellite uplink truck for over a decade for a news organization, but SWM is somewhat different technology than the pro stuff.

 

I'm not 100% sure on the BBC, but I don't think it gets any control data from the receiver. I think it just passively up/down converts the targeted frequency range when it's seen on the cable. The selection is done by the receiver sending the correct voltage/tone combination to the LNB/switch. 

 

In a SWM system there are actually 9 channels. The 8 in the "normal" range which carry a transponder each, and a ninth in the 5mhz range which is used by all receivers to send control commands to the LNB/switch. So, the control mechanism in SWM is more complicated than legacy, which is sending voltages and tones down the line.


Edited by JosephB, 20 November 2013 - 07:46 AM.


#17 OFFLINE   TomCat

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Posted 20 November 2013 - 01:40 PM

What do you mean by lose recordings or just scheduled?  

 The failure mode has been that I attempt to play back recordings and they immediately jump to the "do you want to delete" screen. Sometimes there is a warning that part of a show did not record, probably when it cuts out during the recording instead of before the recording. I have not seen this on any live recording, just those scheduled by SL. But I don't do live recordings.

 

What I don't know is whether I lose a recording if there is no simultaneous recording on the other tuner, or whether it is always when there are two simultaneous. It does seem that if the DVR attempts to record but there is no signal delivered to the tuner, that it is not smart enough to try using the other available tuner. I guess that would be expecting too much.


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#18 OFFLINE   TomCat

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Posted 20 November 2013 - 02:01 PM

Well that's hilarious, because it sends down a transponder, not a channel.  To funny they don't have that right...

 

Actually that terminology is more accurate. Channel is correct, and transponder is not correct.

 

A transponder is a physical microwave repeater/converter inside the satellite, a receive radio, frequency converter, and transmit radio all designed to work together. Physical hardware. A channel, in this case, is anything carved out of spectrum to accommodate a DVB-modulated carrier that is converted from a transponder's frequency to a frequency centered on one of the 8 video channels available in SWM. Once converted, it has no recognizable resemblance to the transponder or the transponder frequency it came from, other than the data info is the same.

 

The signal on the downlink frequency of the transponder is converted to one of those 8 frequencies just before being ported out of the LNB, and the control signal handshakes with the LNB and then tells the receiver which SWM channel it is on so that it can change its LO to allow that channel to be converted to IF. The control signal is at 2.3 MHz while the video channels occupy 970-1870. That implies 8 video channels separated by guard bands of ~14 MHz on average.

 

The transponders? They are still up in space ~23,000 miles away.


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#19 OFFLINE   slice1900

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Posted 20 November 2013 - 02:46 PM

I'm not 100% sure on the BBC, but I don't think it gets any control data from the receiver. I think it just passively up/down converts the targeted frequency range when it's seen on the cable. The selection is done by the receiver sending the correct voltage/tone combination to the LNB/switch. 

 

In a SWM system there are actually 9 channels. The 8 in the "normal" range which carry a transponder each, and a ninth in the 5mhz range which is used by all receivers to send control commands to the LNB/switch. So, the control mechanism in SWM is more complicated than legacy, which is sending voltages and tones down the line.

 

 

The BBC uses nonstandard Diseq signaling. The receiver sends a signal to activate a 2400 MHz LO in the BBC to invert the signal. That makes the B band that is fed from the LNB at 250-750 MHz (which the tuner can't reach, only being able to tune 950-2150 MHz) available at 1650-2150 MHz.


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#20 OFFLINE   slice1900

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Posted 20 November 2013 - 02:50 PM

Actually that terminology is more accurate. Channel is correct, and transponder is not correct.

 

A transponder is a physical microwave repeater/converter inside the satellite, a receive radio, frequency converter, and transmit radio all designed to work together. Physical hardware. A channel, in this case, is anything carved out of spectrum to accommodate a DVB-modulated carrier that is converted from a transponder's frequency to a frequency centered on one of the 8 video channels available in SWM. Once converted, it has no recognizable resemblance to the transponder or the transponder frequency it came from, other than the data info is the same.

 

The signal on the downlink frequency of the transponder is converted to one of those 8 frequencies just before being ported out of the LNB, and the control signal handshakes with the LNB and then tells the receiver which SWM channel it is on so that it can change its LO to allow that channel to be converted to IF. The control signal is at 2.3 MHz while the video channels occupy 970-1870. That implies 8 video channels separated by guard bands of ~14 MHz on average.

 

The transponders? They are still up in space ~23,000 miles away.

 

 

Perhaps calling them "transponders" isn't strictly accurate, but the transponder signal that includes the desired channel a receiver tunes to is carried unchanged (except for frequency) on the wire at one of 8 frequency bands separated by 102.06 MHz. The "guard band" is more like 70 MHz, not sure where you're getting 14 MHz. The transponders Directv uses are either 24 or 36 MHz wide.


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