[alien8]

Day 5 and the carnage continues. ....No Video Signal Detected....... Can anyone tell me the signal strength needed from the "cable company" A cable tv tech will arrive at my house today, I would like to know just what numbers are acceptable for my 3060 to get/keep/use the signal

What meter is used to check the signal strength, and what is dBf...

Dan

#78511

3.0/Build 18



[This message has been edited by alien8 (edited 11-13-2000).]

 

[Serra]

I don't know the specifics for the 3060, but in general the cable signal at the back of the TV should be greater than 0db. 6db would be really good, but anything between 0-6db should do for normal viewing, so I suspect that the 3060 should be near that range. If you can get better than 6db, thank the cable gods.


Remember that splitters cut the signal, so if you have 6db at the wall and run it through a splitter, that might knock you down to 0db!!!


If you need an amplifier to boost the signal, it should go outside your house before the splitter that feeds the whole house. The signal outside should be between 6db and 10db, the higher the better outside, mine is 13db. If you try to boost a signal at the wall, the signal must be at least 1db or you will end up with too much static. I wouldn't even consider boosting at that wall though.


If the signal is very high at the box (out in the yard) and the signal at the house isn't very good, the cable company can replace the underground line from the box to the house. That might help, but they will be resistant to doing that because it requires another service call in most cases.


If the signal outside the house is good, but the signal inside the house is bad, then maybe you can replace the inside wiring to increase signal strength.


Let me know what they say the signal is. Also, if you can, watch the tech when they take the readings. Normally, the tech will just say, "That signal is fine." and will not tell you the actual reading. I had a tech tell me that a -5db signal was in the normal range. This was at the box in the yard. I told him he should call his supervisor and ask what the reading should be. The supervisor told him it should be 13db....

 

[gbuskirk]

I've considered putting an amplifier in my system. Would I be correct to presume that I'd have to put the amplifier after the splitter that feeds my cable modem? The issue is whether the amplifier would attenuate the signal that the cable modem drives onto the cable.


------------------

The Other Glenn

 

[Serra]

Like I said above, if you need an amp, it should be on the feed line into the house in the cable box. If you put it inside the house, you will amplify the noise and the signal and be no better off.


As for the cable modem, yes, you should NOT amplify the signal going into the modem. They do not, in general, like the stronger signals. Also, your amp has to support the higher bandwidths for the cable modem, so you are best off splitting the signal off then amplifying the rest of house.


If the cable company puts in the amp outside (what you really want anyway) they will split the signal for the cable modem off before the amp.

 

[Amazingly Smooth]

I just want to point out that dB is a relative measure of power. 0dB means nothing without a reference point. More accurately:


x dB = 10*log(Po/Pi) where x is relative power difference of Po and Pi, Po is the output power, Pi is the input power, 10* is used to get the d in dB, log is logarithm base 10.


Some common references are used such as dBm which is relative to 1mW of power (10*log(Po/1mW)). dBc is relative to carrier power. dBf is probably relative to the power of the frequency of interest. By specifying a reference power (such as 1mW) then the number is absolute: 0dBm = 1mW.


So if someone says that they are measuring 6dB of power it doesn't make any sense unless they say 6dB more (or less) power than the carrier.


BTW, a lossless two-way power splitter would give -3dB of power to each line relative to the input power.


Cheers


------------------

~~~~~~~~~~~~~~~~~~~~~~~~~

ReplayTV -- The only one that had firewire...


[This message has been edited by Amazingly Smooth (edited 11-13-2000).]

 

[Serra]

Yes, "So if someone says that they are measuring 6dB of power it doesn't make any sense unless they say 6dB more (or less) power than the carrier."

That is correct, so what I should have said was, the tech meter will read between 0 and 6db when he puts it on the line. They will do several different frequencies, but around channel 2, the meter should say 6db. I don't know what their reference is but I assume it is a carrier signal.

 

[billmcf]

I believe that the 0 dB reference is 1 microvolt. Because the reference level is standard across the industry, CATV people just say dB instead of dBuV.


[This message has been edited by billmcf (edited 11-13-2000).]

 

[alien8]

Thank you all for replying to my question. I see the answer will be harder to obtain than I thought. I was hopeing to buy the "meter" at radio shak or Frys, then climb the pole, write down the number... then check the number again in the attic. Moving thru my house, connection to connection, checking the dB drop as I go.

I see now that unless I have some referance point (#) to start with (ie

the cable companies dB# @ that pole location), I would be unsuccessful.

 

[Serra]

A good meter would run you about $1000.00, so it might just be better to let the tech do it. http://www.avsforum.com/ubb/smile.gif

 

[gbuskirk]

There's a pretty good video distribution tutorial at: http://www.hometech.com/learn/video.html


------------------

The Other Glenn

 

[Serra]

Andy5000,

Yes, there are amps with splitters built in, but you could just amp the signal between the first two splitters. That would boost the signal before the split into the house and would most likely remove the loss from the extra splitter for the cable modem.

 

[alien8]

Day 7.

Still have the problem of getting/keeping the signal. After a half hour or less of RF input (ant/catv) the 3060 craps out, then nothing.

Thanks for the link Glenn.

Dan

#78511

 

[alien8]

Uncle Blaine, hope your synching problem stays cured. When I downloaded 3.0 I thought my problems would be over, but it didn't help.

Going to replace my 3060, and if things don't change, then the battle

with the cable company restarts. The saga continues.....no joy in mudville.

Dan

 

[uncleblaine]

I don't know that it is always so simple as low signal strenth. I know absolutely nothing about the synching signals within the signal but was told initially by both Panasonic and Replay that my problem was signal strength. At one point I even used an amp on the RF input which worked for a couple of weeks before back to the blue screen. After many frustrated phone calls to my cable people a tech came out and tested the signal. At the time neither Panasonic nor Replay could tell me a minimum threshold but the meter showed me at 9db which I was told by P and RTV should be plenty. Finally, one of the Replay CSRs suggested the vcr idea as he had done it for OTA channels at his house to help "synch" the signal. It worked. He also mentioned that the only other possible solution he could think of was a time-base correcter. Interestingly, the blue screen nearly always showed up on the lower (non-digital) channels. I know all the output of the Explorer 2000 is analog but for some reason the "digital" channels very seldom showed no signal but the lower "analog" channels did. As I said, so far with 3.0 everything is just ducky. I'm hoping it stays so as it would be very hard to convince myself to take advantage of this new Mercata deal if I had to buy another vcr as well! http://www.avsforum.com/ubb/biggrin.gif


[This message has been edited by uncleblaine (edited 11-15-2000).]

 

[uncleblaine]

Sounds like the problem I initially had with my Showstopper. Try running your signal through a vcr and then to the Replay. It supposedly "synchs" the signal better. I had to run this way for several months after much todo over signal strength. I'd get the blue screen, reboot, and it could be fine for anywhere from an hour to a couple weeks but it always came back. It seems strength never was the problem. It was a synching issue. However, I was told this should be fixed with 3.0 and I have removed the vcr now and so far (1 week) it is working without it. Might be worth a shot. It's not the ideal situation but it's better than the blue screen.

 

[toots]

Quote:

Originally posted by uncleblaine: I know all the output of the Explorer 2000 is analog but for some reason the "digital" channels very seldom showed no signal but the lower "analog" channels did.

Very easy to believe.


On the analog channels, it's just passing the existing analog signal (and all its sync woes) along to your RTV. On digital channels, the decoder box has to generate an analog signal, and most importantly, the analog sync locally. So, for the purposes of the digital channels, it's a moral equivalent to having a time base corrector in your decoder box.

 

[Minnesotan]

I'm a mere mortal (PC and network support specialist by trade, former A/V and video salesman, newsfilm intern, and student producer/director of TV studio production work). While clearly unafraid of the technology, I am also definitely not an engineer.


This forum is a great place for techs to debate whether signal strength, video synch, or timing errors are the culprit that make DVRs occasionally cough up blood over a signal problem that would be handled in stride by a VCR.


But my primary concern, as a (A) consumer and (B) ReplayTV fanatic who wants to see this product achieve market penetration, is: Will the manufacturer please respond to this debate and explain what is going wrong, and what is on the drawing board to correct it? That would give me a great deal more confidence in continuing to recommend ReplayTV to my friends. THANKS.


Jerry

 

[uncleblaine]

Thanks Toots. Makes much more sense to me now.


Minnesotan,


I agree with you entirely. Obviously, I didn't understand what was behind this anomoly myself. I only posted the details of my situation hoping it might somehow help Alien. I share your goal that this be addressed so Joe Consumer will never see it. However, in my initial dealings with Panasonic and Replay as well as my first posts on this forum about it I didn't get much more than an "it works with the vcr, why aren't you happy" attitude. At least not from Panasonic or Replay. Maybe there just aren't enough people having the problem to warrant action. Maybe in a large percentage of cases with similar symptoms it really IS just a signal strength issue the cable companies need to address. I don't know. Don't get me wrong. I love my Showstopper and I want another Replay unit. However, I do believe that the tolerance levels of the Replay (Showstopper at least) need to be addressed before they will get the kind of penetration we all would like to see. I had confidence in the beginning that a solution could be found for the problem or my unit would have been returned. A confidence (or stupidity?)that many consumers would not have had. By the time my confidence ran out, it was too late to return it. After screaming at nearly anyone who would listen about my $600 doorstop the vcr solution was found. I did not believe it should be a forever fix and with 3.0 it is no longer an issue. I'm glad it got to that point and wouldn't give the thing up now even if I end up having to go back to using the vcr. I just don't think most consumers would go through the hassles and disappointments long enough to get "addicted" as I did. It would have simply been returned and all the friends and neighbors would have been told how not only could I not manipulate TV with Replay, I couldn't even watch it.

 

[alien8]

uncleblaine,minnesotan have "hit the nail on the head".

My purchase was a christmass gift for a pair of 75year olds, who would have totally folded under the stress of a non-working unit.

7 days,7 RTV techs + 2 upper level techs, 3 cable techs, lurking in AVS, is way more than the average joe will tolerate.

More isn't always better...

Dan


[This message has been edited by alien8 (edited 11-17-2000).]


[This message has been edited by alien8 (edited 11-17-2000).]

 

[JANVideo]

This problem will have to be fixed the same way the phantom macrovision broadcast signal will have to be fixed. I have the same problem with one of my cable channels. The channel has a very fast "glitch" in the signal, either horizontal or vertical sync loss or distortion, I don't know which one at this time. The only way to see what is happening is to record the same show on a VCR direct from the cable or antenna (not from the DVR) at the same time the problem is showing up on the DVR. This means splitting the signal so it feeds both units at the same time (if you don't already have this kind of setup). Then you have to examine the video tape with a rather expensive oscilloscope or other type of video analyzer to catch the problem. This is what Replay is doing with the macrovision problem (if they ever get a tape from a customer).


This will also show the status of the sync pulses from the channel. This may not be a signal strength problem at all. It may be a simple gating type of noise that is messing up the sync signals. On my system, some of my cable channels are sometimes a little snowy, indicating poor signal strength, yet I never have a problem with the Showstopper ever losing the signal. This only happens with the one channel I have that has a random glitch in the video portion of the signal (including the sync). I also have never seen the phantom macrovision blue screen on any of my channels.


Joel N.