TV3 signal strength

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turb

881 posts

Ultimate Geek

#116274 23-Apr-2013 20:18

I've got a DSE UHF aerial on the roof, connected to the old VHF coax cable, located in Devonport.

I've tried pointing it at Waiatarua and also the sky tower (using the correct polarity each time). On each transmitter the signal strength is about 30% less on the "TV3" mux. Overall the sky tower gives me a better signal (maybe because I can align it by eye).

The poor signal is a problem as I get intermittent pixelation on the TV, and periodic dropouts on my brand new HTPC. Severe loss of WAF ensues.

Is the tv3 mux really lower power, or is there a problem with my setup?

Interests: HTPC, Web App authoring.

RunningMan

8954 posts

Uber Geek

#804552 23-Apr-2013 20:42

Quite possibly the old VHF cable. This can degrade as it ages, especially if water has entered the cable.

Do you know what condition and type the cable is?

Any other splitters / joins etc?

What type of antenna?

turb

881 posts

Ultimate Geek

#804581 23-Apr-2013 22:05

The cable looks in reasonable condition - no visible damage, and I took off about 30cm at each end when I reterminalised with new connectors. No splitters, joins etc. Nice shiny copper seen at both ends.

The aerial is this: http://www.dicksmith.co.nz/product/L4735/dick-smith-hd-uhf-outdoor-antenna-pack on special for $39.99.

I can't understand why it's just the tv3 mux, on two different transmitters, on two different systems.

Interests: HTPC, Web App authoring.

knoydart

904 posts

Ultimate Geek

Trusted

#804593 23-Apr-2013 22:28

The TV works mux are on channels 32 & 33 and should have cross polar discrimination from the 2 sites. Anything else in your rf chain that might contain an RF modulator?

sdavisnz

1015 posts

Uber Geek

Trusted

#804600 23-Apr-2013 22:47

an old friend told me to ajust your UHF (freeview) antenna vertically and not horizontally, better signal aparently, and they are very directional units, very precise, look and see where your neighbours aerials are facing or get a aerial tech to set it up....

regards
steve

grant_k

3539 posts

Uber Geek

Trusted

#804611 23-Apr-2013 22:53

I think you would be quite stunned by the losses you are likely experiencing when using VHF-rated coax at UHF. In the days of UHF Sky, the installers would always insist on running a new coax for the UHF aerial regardless of what condition the VHF coax was in. Your signal strength for all DTT Muxes is probably borderline and it is luck of the draw which ones work OK, and which don't; also it would be affected by local interference sources.

The best advice I can give is to run a new piece of coax through your roof and wall using the old one as a draw wire. You should be pleasantly surprised at the difference it will make. If in doubt, run the new coax directly from aerial to TV through an open window before you commit to removing the old cable. That should prove the benefit beyond any doubt.

turb

881 posts

Ultimate Geek

#804681 24-Apr-2013 08:40

knoydart: The TV works mux are on channels 32 & 33 and should have cross polar discrimination from the 2 sites. Anything else in your rf chain that might contain an RF modulator?

I ggogled Cross Polar Discrimination and got very confused very quickly. Do you mean that it wouldn't matter if my antenna was horizontal or vertical, or that it would matter?

Good thought about the RF modulator, but the coax runs directly from antenna, down the side of the house, under the floor and up through a hole in the corner of the room, straight into the back of the TV.

Interests: HTPC, Web App authoring.

turb

881 posts

Ultimate Geek

#804682 24-Apr-2013 08:45

grant_k: I think you would be quite stunned by the losses you are likely experiencing when using VHF-rated coax at UHF. In the days of UHF Sky, the installers would always insist on running a new coax for the UHF aerial regardless of what condition the VHF coax was in. Your signal strength for all DTT Muxes is probably borderline and it is luck of the draw which ones work OK, and which don't; also it would be affected by local interference sources.

The best advice I can give is to run a new piece of coax through your roof and wall using the old one as a draw wire. You should be pleasantly surprised at the difference it will make. If in doubt, run the new coax directly from aerial to TV through an open window before you commit to removing the old cable. That should prove the benefit beyond any doubt.

I think you might be right on the money.

I did get some new fatter (RJ6) coax cable with the DSE kit. I don't think it'll be quite long enough to take under the house, but I'll do the window thing.

I have a redundant Sky dish next to the antenna. Will it be okay to use the cable from that? (Practically, legally)

Interests: HTPC, Web App authoring.

Lenovo

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grant_k

3539 posts

Uber Geek

Trusted

#804773 24-Apr-2013 10:54

turb:
...
I have a redundant Sky dish next to the antenna. Will it be okay to use the cable from that? (Practically, legally)

I think you'll find it has the wrong connectors fitted, but you could buy some short adaptor cables, or cut off the F-type connectors and replace with Belling-Lee at the TV end if you think you'll never use a satellite dish again. There aren't any legal issues with doing this, so long as you don't have a current Sky contract.

Skolink

1081 posts

Uber Geek

#804940 24-Apr-2013 14:21

I have the same problem in Christchurch. The guy from Radio Spectrum Management who came to investigate my 'interference' assured me that all muxes are transmitted with the same power (200kW) on the same antenna. I would assume the same is true for other sites also.

jaybeedee

64 posts

Master Geek

#823702 22-May-2013 18:44

did you get your problem resolved ?

I'm also in Devonport and while our Tivo receiver shows good signal strength for TV3 and TV4 , they occasionally and suddenly break up and start pixellating badly. Happens on both the 570 and 562MHz. Signal strength is 100% on one of them, 97+ on the other. Haven't noticed it on other channels.

It doesn't seem to be weather related or tied to any appliances being turned on or off.

The problem was first noticed sometime after we reinstalled sky and moved the Tivo to the bedroom. so there has been a combination of changes in the cabling (including the sky techs combining our Aerial and Dish feeds then splitting them again at one of the outlets) and of course the cables I terminated could be dodgy but it seems to only be on TV3/TV4.

KiwiTim

376 posts

Ultimate Geek

#823933 23-May-2013 08:15

I have a similar problem down in Kapiti. My aerial is pointed at the Ngarara Antenna. I have trouble with one mux only (602 or channel 37); whereas the other two are fine (570 & 586).

I should clarify that it is my Hauppauge HVR-3000 DVB-T tuner that has the problem with 602; my Samsung TV can resolve it without much problem.

I'm using RG6 cable. I wonder whether there is some better cable to use, that better shields from interference? On UK websites they mention WF100 cable. Would that be better and where could it be purchased?

turb

881 posts

Ultimate Geek

#823989 23-May-2013 10:14

Yes, rerouting the unused satellite cable worked for me. My connections aren't professional standard but they seem okay.

I still sometimes get a tiny bit of pixellation, but nothing I can't live with.

Because I can see the sky Tower, I have my antenna pointed at that for accuracy even though I think the signal strength may be stronger from Waiatarua [does the inverse square law work in this case?].

I wasted a lot of time up ladders, losing WAF, and fretting about why my nice new HTPC wasn't working.

I know it runs counter to the GZ ethos, but In retrospect my advice would be - "If you have the right antenna, pointed in the right direction, in the right polarity, and you are still getting any reception issues, just get a professional in!"

Interests: HTPC, Web App authoring.

jaybeedee

64 posts

Master Geek

#824412 23-May-2013 20:48

Thanks KiwiTim, I just run my TV through the Tivo but I might look at what happens directly from the TV.

I haven't been on the roof for a while but I think Skytower and Waiatarua are more or less in the same line of sight from our aerial