Poor reception on SOME channels

[Stuntman]

For some reason my PVR-250's are having trouble on some of Adelphia's recently added channels.. the weird thing is that all these channels work perfectly when viewed through all the TV's and VCR's in the house.. but when I look at them in SAGE they look like they are being very poorly encoded.. MOST channels on SAGE look perfect.. just a handful in the upper 60's.. I tried new Hauppauge drivers, numerous reboots.. tried pulling apart all my coax connections and tightening them back down..

It is possible though... and I would love some input..

In order to get cable to all places in my house I have it split from the main line many times.. I have the main line split 3 ways and each of those lines is split twice.. Is it possible that the PVR-250's just aren't getting enough signal? Would it be better to put a signal booster in that setup someplace? Perhaps it would be better to split the main 4 times (1 each to my 2 250's) rather than splitting the 1 line I bring to it into 2..

Any ideas.. anybody share how they split their lines up?

Thanks!

[lotusvball]

I had this same problem and what I did to correct this was move my two pvr 250 cards to different PCI slots. I made sure that they were not in slots side by side of each other. This cleared the problem right up.

[Stuntman]

My cards are already separated by a couple PCI slots... I'm going to try a signal booster made by Motorola which is supposed to help on lines that have too much going on.. I checked my signal strength at my cable modem and it shows it at -19db which is BELOW the minimum of -15db that the specs call for.. so if it is low, I'd guess much of the rest of the house is low.. we'll see!

[SPHurley]

Cable channels above ch62 are >450Mhz. Many cables companies build their systems to go to 450 and are now pushing them well beyond. They may still have some compensation to dial into their system. Higher channels = more loss. Make sure if you buy an amplifier that its spec's go well beyond 450Mhz.

Steve

[mls]

Originally posted by Stuntman
I'm going to try a signal booster made by Motorola which is supposed to help on lines that have too much going on.. I checked my signal strength at my cable modem and it shows it at -19db which is BELOW the minimum of -15db that the specs call for.. so if it is low, I'd guess much of the rest of the house is low.. we'll see!

If you are adding a cable amp before the cable modem be sure to get one that allows bi-directional signal feed (so the modem can feed back out, but there will still be some slight loss going that way).

Also, since those normally do not amplify outgoing singals make sure the cable modem is connected to the first splitter in the line or else its outgoing level will be reduced by the extra amount of each splitters loss in line with it.

Oddly, about a week ago, I had a discussion about this with a friend who has worked in TV repair and apartment cable wiring for many years.

His recommendation was instead of using multiple splitters one after another to use just ONE bigger splitter at the source. That way all lines get an equal signal level (and equal loss from the source). Then just put an amplifier ahead of that splitter with a gain rating to make up for that splitter loss.

Of course if you have one line only 3 feet long and another 100 feet the longer line would add more loss and may require an additional amp of its own.

As a side note... 2 way splitters usually have 3.5 db loss, 3 way about 5.5 db, 4 way about 7.5 db, and a 6 way about 12 db loss.

If you stack splitters one after another, just add up each ones loss to get an idea of how much gain you would need for an amp at the head end of the line.

However, with multiple splitters in line like that and kan amp you could end up with too strong of signal from the first splitter output that could cause overload problems there. Then you might actually need to add attenuators for those lines.

Best way would be to use only one larger splitter instead of stacking multiple ones.

Hey, my friend should know, he's set up to feed 100 TV's in their display room lol.

Hope that helps clean up your end.

[Opus4]

So... I guess my cable repair guy was wrong to tell me that it didn't matter where the splitters were put & in which order? He told me that it didn't matter where/how I split to go from 1 cable input to 5 outputs; the single source signal was still split 5 ways & those 5 outputs would all be even. I don't know whether it will change how I have things set up, but now I'm curious for more clarification.

- Andy

[mls]

Technically, any time you split a cable signal in two you would (logically) only get half the signal level to each output. However, there is also a slight additional loss in the splitter itself.

Half the signal level is a 3db loss. With the additional loss of the splitter itself that normally ends up as about a 3.5db loss to each output.

If you connect a second 2-way splitter to that, it would add another 3.5db loss to the 3.5db loss already from the first splitter.

In other words, anything connected to the 2nd 2-way splitter would have somewhat less than 1/4 of the original signal left, while the other output of the first splitter would have slightly less than 1/2 the original signal strength.

BTW: This also applies going the reverse direction. If you try and put a cable modem on the 2nd splitter feeding back out thru another one before it you will end up with slightly less than 1/4 of the outgoing cable modem signal making back out (our about 7db loss going that way).

This is why the cable modem should always be connected to the very first splitter. Otherwise there may not be enough signal for the modem to connect out properly (even if there may still be enough coming in).

Hope this helps clear up some of the confusion (as well as your cable signals). I know it all sounds confusing... I've just gotten used to how it all works after about 20 years dabbling with computers, reparing TV's, stringing cables, and a bit of Amatuer radio along the way.

Hmm, speaking of needing a terminator to stop things from leaking out... think I just leaked out how old I might be lol.

[SPHurley]

You can buy Pico Macom on line. www.picomacom.com Check out the CDA series of amps. It available as two-way amped and two-way forward amp only. Its also avalable as a one port, two,four. Yes the amp should go first in line. All amps will add some noise to the siginal. The key is to put the amp in lne while the signal to noise is still good. On very large systems splitters are only used to split the main trunks. From there we use directional couplers to minimize the loss on the trunk and keep the isolation between the customer and the main trunk as high as possible. And yes you MUST terminate all unused ports on a splitter. Leaving them open can cause ghosting and other problems.

Steve

[mls]

There's also one other thing to watch out for with splitters. There are still a few older splitters floating around that only pass 5 - 500MHz frequencies.

Most cable systems have gone far beyound that range now, so make sure your splitter(s) are rated to handle 5 - 1000MHz.

I had accidently put one of those older splitters in-line here and all the higher channels turned to snow.

Also, the incoming feed for my cable modem is at 681MHz, so of course my modem would not work either.

There's a LOT of other things to be considered rather than just screwing a bunch of cables together.

SIDE NOTE: Thanks for the tip and website link for the amplifiers Steve.

[Stuntman]

I put the line coming from the Cable company into the amp, and from the amp to the first splitter. I used the following from Motorola.
http://broadband.motorola.com/consum...ignal_booster/

My cable modem went from a -19db to a -9db and the channel issue I was having with Sage seems to have gone away. It might just be my imagination, but it seems now that the white balance or contrast is out of whack on some of those stations.. the whites are too white.. could this be due to the booster?

Thanks everybody!