Problem with UHF/VHF Aeiral

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cldlr76

289 posts

Ultimate Geek

#60865 4-May-2010 18:12

Hi,

I have UHF and VHF aeirals which is going through a dipelxer into one feed and then into the house. Problem is I can't pick up Freeview HD, or Prime or Maori TV, but the VHF channels get picked up ok.
When I bypass the diplexer and go straight from the UHF aeiral I can pick up Freeview HD, and Maori TV but not Prime. I have also tried another diplexer but that didn't fix the problem either. Is it possible the UHF signal is only just strong enough to get Freeview but when mixed with VHF the signal quality drops to below whats required, and therefore I'm screwed?

And in case you are wondering why I want/need both VHF and UHF, the TV's in the bedrooms don't have Freeview tuners and I don't want to buy boxes for every other TV.

Cheers

richms

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#326586 4-May-2010 19:08

Diplexers lose about 2dB on each of their passthrus.

Also it may be an amplifier too if it was installed by sky ages ago. Post a pic of inside it and we will know for sure. Those only amplified the UHF so if there is no power supply then you get virtually nothing out of them.

Richard rich.ms

cldlr76

289 posts

Ultimate Geek

#326589 4-May-2010 19:19

I won't be able to get on the roof until Friday now. It did have a gain control knob, which just continually turned and didn't feel like it was actually doing anything. There is no power supply though.

Is there something else I could use to mix the 2 signals?

richms

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#326599 4-May-2010 19:57

If there is a gain control then it has an amp and needs power.

Otherwise just swap it out for a passive diplexer, but if there was an amp installed in the old days of sky UHF then the signal is probably weak there anyway, but dvb-t needs less signal than analog needs to be clear, so a passive one may be ok for you.

GME Kingray power supplies often come up on trademe for cheap, otherwise try just joining them together and see what happens

Richard rich.ms

cldlr76

289 posts

Ultimate Geek

#326608 4-May-2010 20:07

When you say just join them do you mean with the passive diplexer or some other way

richms

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#326635 4-May-2010 21:01

I mean try just twisting them together and see what you get till you can get a proper diplexer. mismatch shouldnt be too bad because the antennas are totally different, may get a bit of ghosting on the VHF stuff because of what the UHF gets but that better than no freeviewhd till stuff arrives.

Richard rich.ms

cldlr76

289 posts

Ultimate Geek

#326642 4-May-2010 21:12

Cool thanks for that I'll give that a go.

cldlr76

289 posts

Ultimate Geek

#328683 10-May-2010 19:54

I tried mixing the signal with a indoor mixer I had lying around and I still get nothing. The UHF aerial is towards the bottom of the pole so I might swap the VHF and UHF around and put the UHF on top instead and see if that makes a difference.

Out of interest can anyone tell me if I should be able to get a decent signal in Torbay, close to the deep creek reserve if you know the area.

kiwisat

147 posts

Master Geek

#328723 10-May-2010 22:57

You are very close to the Forrest Hill transmitter, but you need to polarize your antenna to vertical for maximum gain. The transmitter is at the top of Forrest Hill beside the water tank. I would suggest you run a single cable directly from your UHF antenna, split it at the antenna to send one leg to the diplexer for the rest of the house, and the second leg direct to your Freeview. You should have heaps of signal where you are.

richms

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#328727 10-May-2010 23:08

I didnt know there was another one in forest hill. Not on any maps I have seen, but I havent driven past the water resovar up there for ages.

Best bet IMO would be the pine hill site, its horizontal and pretty easy to see, just look where all the others are pointing too.

I dont think you will have too much luck with the skytower from all that way up.

Richard rich.ms

kiwisat

147 posts

Master Geek

#328733 10-May-2010 23:29

Yes correct, H and Pine (forest, woods, etc, senior moment) Hill. Main point is he is very close to it.