Pixelating noise with TW Explorer 8300HDC ... need better amp?

[kool cable]

I'm out in the boonies, literally at the end of line for my local TW cable service ... it was something like a 1/4 mile extension from previous end-point to reach me.

My internet service is OK as is the analog cable TV signal. However, my digital service through a Scientific Atlanta 8300HDC pixelates often on several channels, but not all of them, nor all the time. The weather, time of day, year, etc. seem to have a large effect on the digital signal. The TW service guys never find anything, other than a marginally low signal strength, but "within spec".

I have 100' RG11 run from the road, I've eliminated all the old 900 MHz rated splitters, replacing them with a high-end indoor distribution amp (Electroline) rated to 1000MHz, RG6 then runs to the various rooms. I have good, clean signal for analog & high-speed internet, but I am now wondering if the amp is not fully passing the highest frequency digital signal?

My question is, what is the high-end frequency requirement for an amp to support a Scientific Atlanta Explorer 8300HDC (e.g. what is its frequency range)? Alternately, does anybody know a source to find the frequency vs. digital channel assignments for TW Rochester service? Note: TW support seems unable/unwilling to answer this ... they just want to send a service guy out as an answer to any problem ... problem unresolved after 3 or 4 visits.

Finally, this is my 2nd cable box ... same random pixelating ... is the SA DVR-box simply a poor device for handling marginal digital signals?

Any recommendations? Thanks in advance.

[cablewithaview]

100 foot RG11 to the house and an amp to boot. My question is, is the internet flaking out along with the box? Digital runs out at 7-10db below analog levels and if it's outside of a -12 to +12 window then it would cause some pixel. 100ft loses 3.65db of signal, so if the tap has 18db out, you should have roughly 14.35db at 750 mhz hitting the splitter, then what ever the insertion loss is depending on the splitter/s used. If this is the case, you should be ok. However it does not mean that something can't be wrong causing the data packet to the box to be corrupted. It could be a connector, splice, splitter, amp or the wire itself. I had one the other day that had the same issue, after checking the signal, I had +27 at the box!!! So the system techs came out to find an amp that was set way to high. They corrected the problem and the issue was resolved. You could try a different outlet and TV and see what it does yourself.

The weather does play a part on digital and analog pics, it's easier for the digital to be corrupted if the path of the signal is compromised. Basically the up link of a digital signal, then sent to a satellite base station to be received and put on the system will get inference in between satellites. Every March and October, the sun crossing paths over the equator will also interfere with the path of satellite signals since the sun crosses in between the satellites uplinks and downlinks (very rare and in extreme circumstances). Heavy rain and thick clouds can cause issues as well. All of this effecting the head end site, not the customer home.

Digital, and IP based products are usually above 550 mhz (ch.78), but every system is different. Most operators don't want to discuss channel assignments to much especially for certain services.

In the end, would a Moto or Pace box be any different? No if it's not designed that way.

[kool cable]

Thanks for quick feedback.

A couple of years ago, the local TW had shifted the frequency assignment of the digital broadcast channels such that my existing 900 MHz rated splitters were acting as filters for the channels assigned to 2 ~13. This was not revealed until they sent a tech out to look at the problem. We bypassed the splitters and ran direct to the cable box, and those channels reappeared.

Also, the TW tech measured something on the order of -1 dB at the end of the RG11 run coming into my house, but said the signal level at the pole was "within spec" ... he wouldn't tell me what that was. For some reason, he replaced the indoor amp the previous homeowner had installed with one of TW’s generic amps ... it really made no discernible difference, however. He also patched-in an odd arrangement with the Internet tap ahead of the amp coupled with a -6dB inline attenuator. I suspect the cheap amp did not have a return path for the cable modem. Neither the picture nor Internet speeds were stellar, but they were serviceable. From this point forward, I was determined to not let them waste my time tinkering and to fix this myself.

I replaced the cheap amp-tap-splitter arrangement with an 8-way Electroline distribution amp, +3 dB forward, 0 dB return. This improved things, plus I could now move my cable modem to any room. This is good 90% of the time for digital cable as well.

When the pixelating returned again this summer, I was concerned about the low signal level incoming. I have since added an Electroline frequency compensated amp (+7 dB at low end, +14 dB @ 1000 MHz) outdoors at the head of the RG11 run from the pole. This made the analog picture even better (no more stray noise in picture) and stopped the digital pixelating on all but the lower channels (those that were re-assigned to something above 900 MHz). This is what has me wondering if those frequencies might be close the 1000MHz frequency limit being amplified … I’m not sure of the frequency roll off, but I expect it is a steep above 1000 MHz.

Also, I suspect the signal level coming in from the pole is varying widely with time and conditions ... extremely difficult to trouble-shoot an intermittent condition, particularly attempting to work with the cable-tech's scheduling.

Today, everything is great, all channels, all services, so not much to trouble-shoot via trial & error method. Any recommendations on a signal strength meter? Thanks.

[cablewithaview]

Well with a -1 at the end of a 100 ft RG11 drop makes me a little suspicious of what the level is at the tap. That would roughly be a +5 at the tap, maybe a 2 port 4 tap (basically like a two way splitter) at the very end of the line. At 865 mhz, 4 db of loss, at a 1000mhz, 4.4db loss per 100ft.

As for moving your modem around, sometimes that can cause a problem especially if the original install had the line dedicated. Very seldom does someone move a modem around, but if they do, it will flag as an out of spec and they send us out to find out why it's out of spec because the signal is outside it's limits. Others times we are flagged is if the modem s unplugged. Of course I'll hear something like, "O' my computer is in the shop."