High DVB-T Signal but low Quality

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mruane

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Ultimate Geek
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#28884 15-Dec-2008 11:39

Hi

Over the weekend I had trouble with Mt Fitzherbert - Wellington TV3/C4. In my case, the Signal strength was quite high at about 90%+ but the Quality was very low - less than 10%. These figures are what my Panasonic 850Z with Freeview Tuner reported.

Reading Cyril7's response to another poster, advising that Quality is a measure of the Signal to Noise on the transmission, I wondered what could explain a very low Quality level with good signal strength. Does anyone have any idea how this can occur?

During the same period, the remaining transmitters at that site were all delivering good signal strength (i.e. 90%+) and good Quality (also 90%+). So the TV3/C4 transmitter was the only one delivring poor Quality.

Cheers Mike

Quidam

291 posts

Ultimate Geek

#184275 15-Dec-2008 14:20

This is unlikely to be helpful for your particular case, but some time ago I inadvertantly changed a high quality cable with a low quality one.

The results were rather odd, in that some channels were still OK, but others (and I think TV3 was one of them) were not. I theorized it was to do with the ferquency range of the channels as to whether the budget cable was able to handle them or not.

In other words, in the unlikely event you have messed with your cables, take a look at that. It might even be something as simple as a slightly loose connection, or maybe there is some sort of new interference that has just been introduced near your house.

"There is no way to Peace -Peace is the Way" (A. J. Muste)

mruane

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#184297 15-Dec-2008 15:19

Ummm, that actually is helpful! I had changed cables around as I reorganised the living room - it was after that change that the TV3 signal quality diminished. Perhaps I do have a "dodgy" cable. Good suggestion - thanks. I will recheck all of the antenna cabling.

Cheers Mike

richms

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#184355 15-Dec-2008 18:32

Also check you are not looping the RF cable thru something with a modulator that will be affecting the DVB channel

That would lead to it being bad if the VHS or whatever was turned on and crapping over the signal. Authough wellingtons are all on higher channels and modulators are normally between 32 and 38....

Richard rich.ms

Quidam

291 posts

Ultimate Geek

#184383 15-Dec-2008 19:42

Hope you find it. I most definately recommend quad-shielded cabling. The ready-made cables you can buy from Dicks Smith are rubbish and simply don't cut it for UHF DVB-T

"There is no way to Peace -Peace is the Way" (A. J. Muste)

mruane

420 posts

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#184419 15-Dec-2008 23:41

OK, I checked the signal strength and quality again this evening and the Quality is now back up to nearly 100% without any changes to the cabling. I guess this has to be caused through some work at (or near) the transmitter.

@richms, the antenna coax is being fed through an HDR (Hard Disk Recorder) before it reaches the TV so that could be a potential source of RF interference. I am sure the output channel on the HDR is well away from the DVB-T transmiitters I am tuning to, but its something that I will remove from the circuit if I see a repeat of the Quality degradation.

Thanks for the feedback people!

Cheers Mike