Freeview UHF Ch36 issues (Christchurch)

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ashtonaut

614 posts

Ultimate Geek

#210546 1-Apr-2017 15:08

Hi GZ

I'm having issues with reception of the channels on UHF Ch36 (Maori, Prime etc).

Three images are posted here:

https://imgur.com/a/diuMA

The first is Ch34 signal information, which is all OK and these channels work without any issues.

The second is Ch36, which has 100% strength, but very poor quality. As you can see on the TV, this results in lots of blocking and all channels in this block are unwatchable.

The third image is what my antenna looks like.

I'm in Christchurch in an area that Freeview tells me should be fine for signal.

I'm now annoyed with the situation enough to start troubleshooting.

Where should I start? Is there something specific to Ch36 that might explain why only these channels aren't working? Would a new antenna solve this issue?

Thanks in advance!

Spyware

3761 posts

Uber Geek

Lifetime subscriber

#1752702 1-Apr-2017 15:18

The Lincrad is a poor choice of antenna but should be good if you have LoS (line of sight). What suburb are you in??

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ashtonaut

614 posts

Ultimate Geek

#1752710 1-Apr-2017 15:34

Thanks for the quick reply. Yeah the antenna is a relic and has been on the house for years. Suburb is Russley. There is a reasonably bushy big tree (Japanese Maple) about 5m from the aerial so not clear LoS to the hills. I'm happy to replace the aerial, I just need some guidance on what type, and (hopefully) an understanding of why it's only Ch36 that's the issue.

ashtonaut

614 posts

Ultimate Geek

#1752711 1-Apr-2017 15:37

Here's a pic looking toward the transmitter showing relative location of aerial and tree:

https://imgur.com/prMUSNw

andrewcnz

961 posts

Ultimate Geek

#1752873 1-Apr-2017 20:19

Try this...

https://www.matchmaster.co.nz/digital-tv-antennas/02mm-mdu36/

ashtonaut

614 posts

Ultimate Geek

#1752880 1-Apr-2017 20:52

Thanks a lot, I was recommended that unit on the Matchmaster website. Is this one pretty much the same thing?

http://www.freeviewshop.co.nz/large-phased-array-aerial-freeview-p-595.html

I'm also keen to try and understand the physics at play here. Is my current aerial not doing well because it struggles at the higher frequency of the Sky/Korda channel, or because the tree is attenuating more signal at this higher frequency than the lower frequencies of the Mediaworks and TVNZ channels, or something else? It seems a bit strange that two out of three channels work perfectly, that's all.

mm1352000

1149 posts

Uber Geek
Inactive user

#1752900 1-Apr-2017 21:43

ashtonaut: Is my current aerial not doing well because it struggles at the higher frequency of the Sky/Korda channel, or because the tree is attenuatig more signal at this higher frequency than the lower frequencies of the Mediaworks and TVNZ channels, or something else?

In my opinion...

The second guess likely explains more of what's going on than the first. I expect you'd get a fair amount of signal disturbance - reflections and/or partial blockage - as the signal passes through/around the tree and its leaves, particularly on a windy day.

That aerial is a general purpose, fairly wide-band UHF/VHF aerial. It doesn't have particularly high gain. As Spyware said: it can be okay if you have line-of-site, but may not be satisfactory (due to insufficient gain and/or its reflection handling) for more trying conditions.

You only notice problems for the one particular transmission, but if you checked with a spectrum analyser, you may well find that signal in that location for all of the transmitters is close to the receive threshold. In other words: you could say you're lucky to receive the transmissions that you do receive with that aerial rather than the other way around.

ashtonaut

614 posts

Ultimate Geek

#1753002 2-Apr-2017 07:37

OK, thanks, that makes sense. I originally expected to have to buy a new aerial for Freeview, but was pleasantly surprised when I didn't need one - sounds like that was 'only just' and I probably did need a new one.

I also vaguely recall that during winter last year (when the tree didn't have any leaves) that the reception was better on the Ch36 channels - this would further reinforce the tree theory.

I'll check out the aerials in the links above and see if I can get one of those up and running.

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k1w1k1d

1519 posts

Uber Geek

#1753009 2-Apr-2017 08:04

The other thing to look at when replacing the aerial would be to also replace the lead from the aerial to the TV.

Link to the TM seller I bought our lead from.

Aerial lead

ashtonaut

614 posts

Ultimate Geek

#1753232 2-Apr-2017 16:08

So I spent a couple of hours today moving the aerial from one side of the house to the other. Now it's not pointing directly into the tree any more. It is still not perfect LOS as there are trees on other properties further away.

Unfortunately no change to the original issue. I realise it might have been a long shot, but it was worth a try. If a new aerial doesn't fix it then I will replace the lead as well (though that will be a real pain).

andrewcnz

961 posts

Ultimate Geek

#1753266 2-Apr-2017 16:57

Did you have someone watch the signal information on the television when you were aligning the antenna? If not try moving the antenna to the extreme so signal is lost, then move antenna around slowly until the quality moves up. Less signal but more quality perhaps.

ashtonaut

614 posts

Ultimate Geek

#1753276 2-Apr-2017 17:14

Yeah I might need to give that a go, I only had 2 minutes of patience by that point. I'm getting closer to pulling the pin and paying for someone who knows what they are doing to come around.

On that note, can anyone recommend a Christchurch antenna company that know what they are doing and won't charge a fortune?