Diagnosing potential signal quality issues

[Freakitchen]

Hi guys,

I'm having a few problems with recordings breaking up on my media setup. It's seemingly random but on certain recordings, the picture on playback breaks up at intervals - blocking up, pausing, then carrying on. Sometimes this crashes playback - i need to skip past the error point and start playback again.

I've got a feeling this is a signal quality issue. I've had to do a passive split on my aerial output in the kitchen/living room to feed a digital LCD in the kitchen. Can't really get away with disconnecting this TV for any period of time to do decent tests for fear of incurring the wrath of the lady of the house

Was wondering if there's something in the logs that would indicate a signal strength issue, if I was able to match it up to a recording that broke up? Would it be worth trying a different MPEG Mux (could this even cause the problems I'm describing?)

The thing that's confusing me at the moment is the fact that Live TV doesn't seem to have the same problems.

Cheers,
FK

[ACTCMS]

You can find some stuff on checking signal quality in this thread... the ScanChannel utility is worth having in your toolkit...

[Freakitchen]

Thanks for that. Don't have much time to do proper tests at the moment unfortunately, but I'm running two simultaneous recordings as we speak having switched to a Cyberlink Mux (1307 I think). Will see how that goes.

[Anthony]

Are you getting your signal from an ATSC antenna, or via cable using QAM?

I have Comcast cable and despite strong signals, I've never been able to record shows reliably. Like you, I can usually "watch" them OK but recordings occasionally turn out a jumbled mess. I battled it for months before giving up and switching to an antenna.

If you're using an antenna, where is it located? I tried a small set top antenna, as well as a larger DB2 style antenna mounted in the attic. While both provided strong signal levels, I frequently had issues with errors and shows dropping out occasionally. Once I mounted the DB2 outdoors, the errors all went away. I guess it was picking up too much interference from the wiring and/or building materials inside the house.

Anthony

[martint123]

I'm sure in one of the logs is a regular interpretation of signal quality - maybe requires a turn-on with a config.xml flag.

I've found TV sets are more sensitive than TV cards - I guess it's the electrical noise in a PC that "deafens" them a bit.

[Freakitchen]

@Anthony, I'm in the UK so obviously things are different over here. I'm using a dual-tuner Nova-T 500 for over-the-air freeview, with an external aerial. There's a splitter in the loft for the 6 TV points in this house, unfortunately I'm having to use this one point for two devices.

[Freakitchen]

Haven't managed to run the signal testing tool yet, but I think I can confirm that this is a signal quality issue. I was recording two channels at the same time tonight, one on ITV4 that lasted an hour, the other on five that only lasted for half an hour. Playing back the hour-long program, there was significant picture & sound breakup for the first half hour, but it was absolutely fine for the second half hour, once the other recording had stopped.

So, my question now is a hardware one if anyone has any experience with aerial amplification; I suppose I need to boost the signal on this socket with a 2-way amplifier. In the loft, the signal from the exterior aerial is amplified and split for six separate sockets in the house. Will I run into any problems amplifying the signal for a second time in the living room? Should I look for an amplifier/splitter with adjustable gain, or without?

[martint123]

The problem is cable losses.
Best possible config is amplified splitter as close to the aerial as possible with separate cables to each outlet.
The problem with a amplifying splitter at the end of one of these cables is that the signal is degraded by the length of coax, so you start amplifying the noise as well. Certainly worth trying though. I got a variable gain, four outlet one from ebay a month or so ago for 8 quid, so not too much lost if it doesn't improve things.

[Freakitchen]

martin, I was under the impression that it was the 2-way passive split that's causing my problems, I was told elsewhere that using this immediately causes a significant loss on each of the two new paths regardless of whether either tuner is on and running.

Figured the best way to diagnose is to bypass this splitter for a while and run some test recordings. If they work fine, presumably I can say that the signal to the wall socket in itself is okay, in which case I guess my only solution here is an amplifier.

[martint123]

Oh yes, a two-way passive splitter will reduce the signal by half as an absolute minimum.

If one tuner works ok with no splitter then yes, that would seem to indicate there is enough signal there to be amplified and split into two (though if it is really borderline, then the splitter could just push it over the edge).

That's on of the problems of digital, there is little warning that the signal is low, before it suddenly disappears - unlike analogue where you can estimate how weak it is by the increasing noise on the picture.