QAM, HVR-1600, Amplifier?

[pastro]

I'm not sure what didn't make sense, so if it's still unclear after I respond, ask again. I've jsut spent the last day and a half trying to make progress, but still no luck. I'm ready to tear my hair out. (sorry, frustration is bit9ing hard right now.)

OK, answers: The amp plugs in where it is used. I'm going to answer some more questions with responses to others.

The part that didn't make sense is the signal strength going down. SNR maybe, but signal strength wouldn't go down unless the front end was overloaded.
My digital cable box has a great diagnostic screen that shows the signal strength and input level in dbs not as a signal strength meter with no units, so just to make sure you don't have a digital cable box, is that right?

[dennit]

That seems to confirm a cabling and/or connector issue. Higher frequencies are a lot more sensitive to the cable quality than low frequencies.

Yes, I agree that high frequencies are more susceptible to cabling/connector issues. That's why I spent some time confirming that the SNR drops steadily with freq and testing at the highest freq QAM channel. My problem is that the signal arriving at the house is OK, but I can't distribute it without disturbing the high freq end too far for the QAM digital sets.

More accurately - after a lot of work, I am now able to distribute it, by careful selection of the best splitters and sending half of the incoming signal to my HVR1600, one quarter to my digital TV and the remaining quarter through the amp to 5 remaining non-digital locations (TiVos, kids bedroom and kitchen analog TVs, etc.)

You would think that if my most sensitive digital device (HVR-1600) works fine on the worst channels (high freq) after a 50% splitter, then I should be able to distribute the original signal with a decent amplifier to the 8 locations I need.

That would be a good SNR for over-the-air, but if I remember correctly QAM cable needs to be in the 30's to get a reliable lock.

30 is where the WinTV signal meter changes from yellow (OK) to orange (fair-poor). Green seems to be best, but I never see that. If it drops below 30, I do start to have problems. With the 50% passive split of the original signal, I'm at 30-31 SNR on the worst channel.

Unless the incoming cable runs directly to the wall outlet, you'll still be going through the cable wiring in the house. If the cable company terminates their line on the exterior of your house, try running a direct RG6 cable from that point to the HVR-1600 tuner (even out through a window would work for testing). If your signal quality is better, you'll know you need to update the house wiring. If the signal quality is the same, there's no more you can do on your end and will need to contact the cable company.

Sorry, I was unclear. I ran RG6 direct from the HVR-1600 to the exterior connection to test. No splitting. minimum connectors. Signal is still a function of freq. Best is about 34 at low freq end - worst at the high freq end is about 32 SNR measured by WinTV signal meter. Surely it should be possible to distribute this and stay above 30 - or am I wrong? I need 7 locations, only 2 are digital right now.

Forget the amp for now. It's obviously hurting your signal more than it's helping. I had the same problems with an amplifier, and found improving the cable connections had a greater effect on signal quality than adding an amp.

I came to same conclusion - all the amplifiers (and I tried six, from single output to 4 and eight out), all decreased the SNR significantly for the higher freq end. I had to split first for the digital sets, then amplify the split signal for the analog TVs. I'm not very happy, as everything is marginal, but it seems to be working. I do have some RG59 still in the house, but not in the lines going to the digital sets.

That sounds about right for splitter losses.

That's what I concluded.

If I might ask - what SNR are others seeing direct from the cable company over RG6 to HVR-1600 on the WinTV signal meter, and how much loss do they experience when splitting/distributing the signal? Somewhere I saw someone say that a cable installer claimed "they never see 40," but is mine really low at 33-34?

Right now, I can't even split the signal to feed both the analog and digital inputs of the HVR 1600 - as that drops the signal too far for the digital QAM decoding. It's not a huge problem - I'm mostly interested in GBPVR for QAM digital recording/PVR, but it's annoying.

Thanks for the comments.

[dennit]

The part that didn't make sense is the signal strength going down. SNR maybe, but signal strength wouldn't go down unless the front end was overloaded.

OK. I agree that did not make sense. Originally I tested using the TV, and it is marked "Signal Strength" on a scale of 1-10. I suppose that's some helpful engineer trying not to confuse us with an SNR ratio label.

I also considered that the amplifier might be overloaded, but I figured at least one of the amps tested would not overload. Interesting tidbit - one tested amp was labeled Philips on the box and marked 50-900 Mhz on the amp, but specs on the back of packaging said 50-500MHz. The signals I have trouble with are in the 600 MHz range - if I am reading them right.

My digital cable box has a great diagnostic screen that shows the signal strength and input level in dbs not as a signal strength meter with no units, so just to make sure you don't have a digital cable box, is that right?

I'm using the SNR from the WinTV now. It also shows correctable and uncorrectable errors, as well as SNR, but I don't see a signal strength meter.

[crossnet]

I had a similar problem and called my cable company (COX) to get recommendations so I could buy an amp. To my surprise, they insisted on making a service call and they installed a high quality remotely powered unit at no expense to me. Great service and well worth the call.

emr

[dennit]

I had a similar problem and called my cable company (COX) to get recommendations so I could buy an amp. To my surprise, they insisted on making a service call and they installed a high quality remotely powered unit at no expense to me. Great service and well worth the call.

I've got a service call in now, but they seemed kind of doubtful that it was their problem. Do you have any idea what the SNR was before/after they installed the amp?

[pastro]

My cable box needs about 30dbs to have a chance at receiving the signal, 33 or better works with no errors. I had a bad time with mine also and eventually replaced the feed from the outside of my house to my distribution amp. Gained about 5 dBs of SNR.
Signal wise I have around +3dBs.

Putting a remote amp on the old cable worked and improved the snr from 27 to 34, but I had all sorts of interference problems from local channels, replacing the cable fixed that.

[dennit]

My cable box needs about 30dbs to have a chance at receiving the signal, 33 or better works with no errors.

That matches my testing. If I could just distribute my incoming signal, I'd be OK.

Putting a remote amp on the old cable worked and improved the snr from 27 to 34, but I had all sorts of interference problems from local channels, replacing the cable fixed that.

Hmmm. On the high freq. end the amps all made things much worse for me. I'd love to improve SNR with a decent amp. I'm not sure how I'd tell if I've got a problem with local channel interference. I considered buying some RG6q quad shield, but didn't think it would really help.

[pastro]

That matches my testing. If I could just distribute my incoming signal, I'd be OK.



Hmmm. On the high freq. end the amps all made things much worse for me. I'd love to improve SNR with a decent amp. I'm not sure how I'd tell if I've got a problem with local channel interference. I considered buying some RG6q quad shield, but didn't think it would really help.

In my case,wherever there was a local channel I would see wavy lines on the picture, or worst case a ghost of the other channel.

Surpisingly I bought a 10dB remote powered radio shack amp and it worked well above 600Mhz. However the cable modem doesn't work with an Amp in the circuit so I had to use a 2:1 splitter at the house input.
When the cable guy came out we took all the amps out and figured out the homerun from the outside sucked and replacing that helped loads.

Definitely get the cable guy to measure signal and snr at the street, your house connection and at the TV in question. That will help debug this quickly.

[Anthony]

I am now able to distribute it, by careful selection of the best splitters and sending half of the incoming signal to my HVR1600, one quarter to my digital TV and the remaining quarter through the amp to 5 remaining non-digital locations

Yep, I had to do about the same thing. I split my incoming signal in half. One side of that split gets split again, one side going to my cable modem, then I split the other side between my two HVR-1600 analog tuners.

The other half of the first split, goes to a 3-way splitter that sends lines to the TV's in our house (one digital, two analog).

The digital tuners in my HVR-1600's are connected to an outdoor DB2 style antenna run through a single 2-way splitter.

30 is where the WinTV signal meter changes from yellow (OK) to orange (fair-poor). Green seems to be best, but I never see that. If it drops below 30, I do start to have problems. With the 50% passive split of the original signal, I'm at 30-31 SNR on the worst channel.

Yep, that sounds about what I was thinking. With over the air broadcasts, I'm in the green range with about 22-24 SNR (don't recall the exact transition point), but I usually average around 28 SNR. I get perfect reception at that level.

When I fussed with QAM cable, I never got out of the orange range (I was right around 30 SNR I think). The cable tech came out and verified my signal level was "better than most" (whatever that meant), and charged me for a service call. But I never could get it to work. On the other hand, my Samsung TV never has a signal problem, despite running through three different splitters at the time.

For what it's worth, I also tried an "HD HomeRun" and an "OnAir GT" digital tuner, and neither of those would lock on to my cable signal either.

Like I said, I wasted a couple of months battling the QAM situation and got nowhere. Nothing I tried had any real effect on the final recordings. My cable company doesn't really offer any stations via QAM that I couldn't pick up with an antenna, so I switched to over-the-air and haven't had a single problem since I mounted my DB2 style antenna outside.

all the amplifiers (and I tried six, from single output to 4 and eight out), all decreased the SNR significantly for the higher freq end.

You could try an amplifier rated for satellite signals, I think they're rated to 2ghz, but you may tradeoff the low frequency signals with those?

Somewhere during my research, I heard that the HVR-1600 had a problem with Comcast cable in particular, and a fix was on the way. But I haven't heard anything more about it since then.

Anthony

[dennit]

Anthony, thanks for this info. It helps to know that I might do better with OTA than QAM. I'll do some research on DB2 antennas (I haven't looked at OTA much). I am on Comcast, so that was good info, too. Perhaps there is some patch or upgrade for the 1600 to deal with QAM on Comcast.