Mains interference: Digital TV problems

On Sat, 10 Jun 2006 13:38:33 GMT, Dave Ryman Gave us:

My "off air" HDTV reception is fine using a set top antenna. Try one. You mat find that your in wall post wire installation of your antenna feed has some "RF holes" in it. At least big enough to let the noise from an AC appliance affect it.

Rabbit ears work great on my HDTV off air tuner.

Roy L. Fuchs wrote in news: snipped-for-privacy@4ax.com:

I don't think we'd get enough gain from such an aerial - our geography is such that an aerial on the ground floor probably won't be high enough.

On Sat, 10 Jun 2006 19:29:02 GMT, Dave Ryman Gave us:

OK, then is the coaxial cable run from you antenna to your tuner a "home run"? That is a single cable run, with no breaks (unions) in it. You have at least ONE as you are getting it from a wall outlet. If you have enough slack in the wall, remove the wall plate, and bring the cable out "flying lead" style.

Each break costs a couple db.

Roy L. Fuchs wrote in news: snipped-for-privacy@4ax.com:

(snip)

That's interesting - mind you, I always thought that standard coax connectors were a bit hopeless. Any thoughts on BNC connectors?

Looks like I'm going to try replacing the whole length of cable - wish me luck!

Thanks for all the advice.

its also bullshit. conector loss might be about .1 dB.... granted having as few splices as possible is a good thing.

mind you, I always thought that standard coax

check the easy stuff first.... look for an open balun on the antenna.

"TimPerry" wrote in news:mbCdnQUolIUf7xbZnZ2dnUVZ snipped-for-privacy@adelphia.com:

(snip)

Just looked "balun" up. Our aerial is a new one. Am I right in assuming that, in our case, the balun is the small plastic box on it within which the coax attaches? If so, ours is fine. If I'm talking B*llocks, then someone please let me know!

restating the problem:

" We have the now common set-top box for digital terrestrial TV and radio.

We get a lot of intereference: Picture break-up and loud clicks in the sound. Sometimes making a programme unwatchable. We have managed to reduce this: The aerial has been upgraded, and there's a filter on the mains socket supplying the AV equipment.

However, we get serious problems when we have a fan running, the washing machine is on, or we run the hot tap (It's one of those that turns on a heater to heat the water as you use it)."

to me this sounds like some kind of ground loop issue.

just try this: get 2 low cost baluns. they have an F connector at one end and 2 spade terminals at the other. solder or bolt the spade lugs to the matching lug on the other balun. this gives you a 75 ohm F connector at each end. add a short male - male cable and insert at the receiver.

if this does not help then you can proceed to more drastic and expensive measures.

Dave,

I assume you are in the UK.

It's possible that the signal strength of the digital signal is marginal - which would cause the symptoms which you describe.

The digital transmitters run at much lower powers (~10kW ERP) as opposed to the analogue transmitters (can be up to 1MW ERP) and although you may be getting a satisfactory analogue signal the digital signal may well be near to the receiver's threshold.

John

On Sun, 11 Jun 2006 00:52:11 GMT, Dave Ryman Gave us:

Standard F are fine done properly, and you will end up with more breaks in the line with BNC as you'll have to convert back and forth to hook up to all standard gear.

Yes, you must cut (prepare) all of your fittings carefully as well.

On Sun, 11 Jun 2006 05:12:22 -0000, "John" Gave us:

It all comes down to bit-error-rate with digital. Once it gets above ten percent, anomalies start to appear. Picture gets artifacts, sound drops out... entire image goes blank, no sound.

Roy L. Fuchs wrote in news: snipped-for-privacy@4ax.com:

By F-connector, I assume you mean the metal connectors that screw onto the shielding and outer insulation of the coax, and have the wire sliding into a centre pin. I have actually found one of these now that has a grub screw to make contact with the main centre wire: The standard ones here in the UK usually just depend on the wire making contact by sliding into centre pin - very hit and miss. I trust the average water pipe connector more - and that's saying something!

Thanks for that.

"TimPerry" wrote in news:9vedndrrue5uChbZnZ2dnUVZ snipped-for-privacy@adelphia.com:

That sounds like it's worth a try. I've being researching baluns, and my head now hurts.

Thanks.

"John" wrote in news:cLqdnQRV0 snipped-for-privacy@pipex.net:

Yep, in the UK. I suspected the power used to transmit digital was poor, but didn't realise it was just 10% of the analogue signal - no wonder there's problems! And they want to turn the analogue off in a few years: They must have shares in the companies that make aerials, coax and connectors.

I live in a margin area and the digital signal does tend to drop in and out exactly as you described in your OP. It's also weather dependent - the hotter summer months are worse than the cooler winter/spring/autumn.

I would firstly check all your connectors and ensure the centre of the coax is soldered to the centre pin of the plug (for our US readers we don't use F type connectors for Terrestrial TV, they're only found on satellite equipment).

Then if the connections are sound, try to get the aerial checked by someone who is competent - look for someone who is a member of the CAI Confederation of Aerial Installers.

Like you I'm also wondering about the analogue turn-off. Hopefully they may be able to up the power of the digital transmitters once the analogue TXs are turned off and the spectrum is freed up.

John

"John" wrote in news: snipped-for-privacy@pipex.net:

(snip)

I wouldn't bank on it - the whole thing seems to have been done on the cheap with no real thought for the viewers - logos on-screen which risk burning-in on your TV screen, a useless program guide, and equally useless Teletext.

Thank god for DVDs!

i had assumed that you had a solid signal except for the interfearance problem.

another possibility is to add a inline amplifier at the antenna. this boosts the signal a bit. it is then attenuated by the length of coax. a inline section is added at the receiver end to power the amplifier.

it looks something like this

i understand you have to license TVs in the UK. would that apply to the digital box too?

CAI membership doesn't count for much. Their members give *very* variable service. Some of the best aerial installation companies out there are not members so go by recommendation and read up on the subject. If it costs more than £100 just to get a decent aerial signal you may as well go FreeSat.

See uk.tech.digital-tv where this would be more on-topic.

-- Adrian C

I always considered CAI installers as being in the upper part of the quality range - perhaps mistakenly.

For a marginal area Freesat is probably the way to go. I've also heard some horror stories about Sky's installers but that's for another thread.

Good Luck

John

On Sun, 11 Jun 2006 13:07:28 GMT, Dave Ryman Gave us:

Not really. A digital signal is easier to retain all of the signal due to the fact that a lot of FEC gets sent with the signal.

I use a regular antenna. I only miss on one local station. I actually used to get it from 20 miles farther away... over hills.