Digital over Aerial - no tv3 or 4

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rjbathgate

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Geek

Topic # 87323 25-Jul-2011 22:44

Hi,

We're in Tauranga, and have just installed a new digital freeview tv, and are having trouble with receiving TV3 and Four.

Channels 1,2 and all others are all good, while 3 and Four, no service.

I seem to remember from the past that TV3 and Four broadcast on either UHF or VHF whilst all others are on the other (VHF or UHF) so am thinking some issue lies here? Or am I barking up the wrong tree?

The TV is returning the following on signal tester:
TV1/2 etc: Strength 10 / Quality 4 / Actual picture, perfect
TV3/Four: Strength 7 / Quality 0-1 / Actual picture, none "No Service" message --> odd that there is a good signal strength still?

There is a masthead amp installed (which is required - turning it off looses TV1/2 reception)

And on analog, TV3 is received just fine and dandy.

Up in the loft the setup is as follows:

VHF and UHF aerials (two separate) --> diplexer --> mast head amp --> tv

The masthead amp input goes into the input marked UHF/VHF.

The diplexer currently has BOTH UHF and VHF inputs connected on the same input (either marked UHF or VHF, cannot remember at moment, but def marked as just one.)

So I have tried separating them, putting on aerial on one and the other across the other (I'm not 100% sure what aerial is UHF and VHF so tried both ways), and neither fixed the problem.

In fact, with it one way round (so with each aerial on it's own diplexer input), we could get TV3/Four but then lost everything else. And the other way around (with each aerial still on it's own diplexer input, but the other way around), we got TV1/2 etc but no 3/Four.

Now, I have it as it was originally setup before I went into the loft, with both aerials going into the ONE diplexer input, and achieve everything bar TV3/Four.

Where do I go from here? Any suggestions and ideas most appreciated.

Thanks in advance
Rob

RunningMan

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Reply # 497862 26-Jul-2011 08:47

The Freeview digital signal is broadcast on UHF only. Unless you still need your old VHF (the larger) antenna, I would disconnect it, along with the diplexer.

Try running the UHF antenna (usually the smaller one) directly in to the TV, and see what happens - if no luck with that, reconnect the amplifier and try again.

Let us know what the outcome is.

simon14

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Reply # 497863 26-Jul-2011 08:48

We have UHF Freeview HD too and all channels used to work fine but now tv3 and Four have no service. Sometimes they come back on but this is very rare.

We are in Auckland so it's not related to location.

For freeview HD, do all channels get broadcast from the same location? (ie, via freeview) Or is it like analogue TV where tv3/4 have their own transmitters in different locations to TVNZ?

I could be wrong but i think it's just a signal issue to mediaworks transmitter.... From what i assume, UHF doesn't need line of sight like digital via a dish, but maybe it's the hills/trees causing loss of signal???

Spyware

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Reply # 497872 26-Jul-2011 09:02

simon14: We have UHF Freeview HD too and all channels used to work fine but now tv3 and Four have no service. Sometimes they come back on but this is very rare.

We are in Auckland so it's not related to location.

For freeview HD, do all channels get broadcast from the same location? (ie, via freeview) Or is it like analogue TV where tv3/4 have their own transmitters in different locations to TVNZ?

I could be wrong but i think it's just a signal issue to mediaworks transmitter.... From what i assume, UHF doesn't need line of sight like digital via a dish, but maybe it's the hills/trees causing loss of signal???

All DVB-T H.264 channels are on same site in 3 muxes using 3 transmitters on 3 frequencies.

Ross

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B1GGLZ

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Reply # 497876 26-Jul-2011 09:18

RunningMan: The Freeview digital signal is broadcast on UHF only. Unless you still need your old VHF (the larger) antenna, I would disconnect it, along with the diplexer.

Try running the UHF antenna (usually the smaller one) directly in to the TV, and see what happens - if no luck with that, reconnect the amplifier and try again.

Let us know what the outcome is.

+1

Remove the VHF aerial completely as it is probably interfering with the UHF antenna's reception if it is close to it. I had this problem doing a recent installation in a fringe area and it sounds as though you are in a fringe reception area. How old is your antenna and co-ax?
Also check the anenna alignment carefully. A few degrees either way can make a big difference.
As above you need a UHF antenna only (in very good condition) with a single straight run of good quality (RG6) co-ax to the TV. Then add the amp if that doesn't work. Old co-ax can cause massive signal degradation.

simon14

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Reply # 497880 26-Jul-2011 09:23

Spyware:
simon14: We have UHF Freeview HD too and all channels used to work fine but now tv3 and Four have no service. Sometimes they come back on but this is very rare.

We are in Auckland so it's not related to location.

For freeview HD, do all channels get broadcast from the same location? (ie, via freeview) Or is it like analogue TV where tv3/4 have their own transmitters in different locations to TVNZ?

I could be wrong but i think it's just a signal issue to mediaworks transmitter.... From what i assume, UHF doesn't need line of sight like digital via a dish, but maybe it's the hills/trees causing loss of signal???

All DVB-T H.264 channels are on same site in 3 muxes using 3 transmitters on 3 frequencies.

Well there goes that theory.

Any other ideas why tv3/4 dont work then?

rjbathgate

47 posts

Geek

Reply # 497898 26-Jul-2011 09:51

B1GGLZ:
RunningMan: The Freeview digital signal is broadcast on UHF only. Unless you still need your old VHF (the larger) antenna, I would disconnect it, along with the diplexer.

Try running the UHF antenna (usually the smaller one) directly in to the TV, and see what happens - if no luck with that, reconnect the amplifier and try again.

Let us know what the outcome is.

+1

Remove the VHF aerial completely as it is probably interfering with the UHF antenna's reception if it is close to it. I had this problem doing a recent installation in a fringe area and it sounds as though you are in a fringe reception area. How old is your antenna and co-ax?
Also check the anenna alignment carefully. A few degrees either way can make a big difference.
As above you need a UHF antenna only (in very good condition) with a single straight run of good quality (RG6) co-ax to the TV. Then add the amp if that doesn't work. Old co-ax can cause massive signal degradation.

Hey

Thanks for the replies.

Re age of co-ax and antenna, not sure sorry, probably at least 10+ years.

Re alignment of antenna, how do I actually check it - what can I check it against?

Off to disconnect VHF and go direct UHF -> TV now and see what happens. Will let u know.

Cheers

rjbathgate

47 posts

Geek

Reply # 497917 26-Jul-2011 10:35

Hi

Removing one aerial = better. Finds 3 and 4 but not perfect reception. This us with amp. Without amp, pretty much nothing.

The aerial to amp is rg59. Should I replace with 60?

Cheees

RunningMan

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Reply # 497933 26-Jul-2011 11:13

If the coax is 10 or so years old, it may well be full of moisture, and no longer working to it's best. Replacing it with RG6 would be a good idea.

As for antenna alignment, it will be trial and error. Try moving it slightly left and right, a few degrees at a time, and see if it gets better.

Was your original (analogue) UHF reception OK?

lonney

85 posts

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Reply # 497950 26-Jul-2011 11:45

DTT coverage in Tauranga is provided from Kopukairua and Te Aroha. Kopukairua is closer so it'll provide a stronger signal, shouldn't hard to figure out where to point your antenna.. - check the coverage maps on http://www.freeviewnz.tv

Like the others say, disconnect the VHF antenna and diplexer.

If it's an old installation check the condition of the UHF antenna, and where the balun is attached (black plastic box that the coax goes into on the antenna), if there any corrosion on the connections or evidence of water, ideally it needs to be cleaned up or replaced.

If you want things to last apply some spay on lanocote to the metal on metal connections so they don't corrode.. Also check that water hasn't gotten into the coax, peal back some of the insulation, if the copper is black (or anything but shiny) throw it in the bin and get some new stuff - RG6 and keep the run as short as possible, more cable = more attenuation.

You shouldn't need a mast head amplifier, unless you're in a deep fringe area, in that case it's just as important to have antenna and cables in top condition. Like any system, it's only as good as the worst part :)

rjbathgate

47 posts

Geek

Reply # 497970 26-Jul-2011 12:27

Hey

Having replaced aerial -> mast head amp with new RG6 and then from masthead straight to TV, we have it all working ok.

All signs are they we do need the amp -- we are in a small depression of land, and our neighbours need one too so...

The strength and quality jump around a bit on the TV's signal tester, but there is no (touch wood, yet) interference on the picture)...

Fingers crossed when the rain comes it still works...

Cheers all for your help
Rob

RunningMan

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Reply # 497983 26-Jul-2011 12:49

Excellent - glad to hear it!

B1GGLZ

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Reply # 498008 26-Jul-2011 13:30

rjbathgate: Hey

Having replaced aerial -> mast head amp with new RG6 and then from masthead straight to TV, we have it all working ok.

All signs are they we do need the amp -- we are in a small depression of land, and our neighbours need one too so...

The strength and quality jump around a bit on the TV's signal tester, but there is no (touch wood, yet) interference on the picture)...

Fingers crossed when the rain comes it still works...

Cheers all for your help
Rob

Great stuff.
Just shows what new good quality co-ax and a new antenna can do.
Exactly same result as I had in a fringe area but I didn't need the amp.
To get exact direction to point have a look for the Transmitter (and yourself) on Google Maps and then point your aerial direct that way. Look for a landmark in line with you and the TX that you can see. Slight variations of direction can make a big difference.
Glad to hear its working OK now.
With new antenna and co-ax hopefully the rain shouldn't be a problem.
By the way, on Freeview you don't (or shouldn't) get interference as it's digital. The picture is either perfect or pixellates and drops out with fluctuations in signal strength or disappears altogether.