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6 posts

Wannabe Geek
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Topic # 190993 19-Jan-2016 12:57
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I'm about to add a UHF antenna to our place on the eastern side Glendowie, and I'm going to try and put the antenna in the roof cavity (colour-steel roof), but right up by a plasterboard gable that opens directly towards the Sky Tower.

 

So to give myself the best shot at pulling this off, I figured I might as well get the highest gain antenna I could find, and if I get no luck in the roof I'll go with a pole off the roof.

 

So I'm selecting between a 43 Element and 91 Element antenna and just wondering if there is such a thing as too much gain? Do I need to be careful getting a 91 element beast (apart from the size)?

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Uber Geek
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  Reply # 1474611 19-Jan-2016 13:44
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You would get away with it if your roof was concrete tile not so sure about colour steel metal seems to block signals quite well even with a high gain antenna the other thing you'll need to watch is the power of the signal at the box you wish to plug it into you may need to plug in an attenuator between the end of the cable and the box,  atleast when I was installing sky that's what we were told to do as it can cause the tuner to burn out   

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  Reply # 1474637 19-Jan-2016 13:55
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I'm not sure Athlonite read your post properly, and I'm not sure they proof read their own because it's pretty awful to try to decipher.

 

Give it a shot, through wood your changes are pretty good. Just make sure you can actually get the antenna up into the ceiling cavity.




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Wannabe Geek
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  Reply # 1474898 19-Jan-2016 21:15
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Yeah good point about the size, I might wind up assembling it up there!

 

Another quick question - I seem to have a mix of neighbours pointing to Waiatarua and the Sky Tower.

 

Here is my chart for Waiatarua

 

 

 

 

And here is my chart for the Sky Tower

 

 

 

 

 

 

Oddly matchmaster.co.nz suggests Waiatarua and a Phased Array (which I see *none* of around here). Given it's higher transmission power is Waiatarua likely to be stronger over 28kms vs Sky Towers's at 10kms?

 

Also I notice there is some differences in the channel frequencies between the two towers, do both broadcast all the same channels?


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  Reply # 1474905 19-Jan-2016 21:29
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I'd probably remove or mask your address, just out of an abundance of paranoia.





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Uber Geek
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  Reply # 1474955 19-Jan-2016 22:06
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I'm 59km from Wharite in the Manawatu and that site also recommends the array. Compared to the 43 element that we have the array would probably be better in the wind and attract fewer birds. Our aerial is side on to the prevailing wind and tends to rotate on the pole. I've added some bamboo skewers and nylon line to make it less comfortable for the flying guano donors.

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Ultimate Geek
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  Reply # 1474972 19-Jan-2016 22:30
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rh2600:

 

snip..

 

Oddly matchmaster.co.nz suggests Waiatarua and a Phased Array (which I see *none* of around here). Given it's higher transmission power is Waiatarua likely to be stronger over 28kms vs Sky Towers's at 10kms?

 

Also I notice there is some differences in the channel frequencies between the two towers, do both broadcast all the same channels?

 

 

 

 

I get the sudden hint that matchmaster either do not know or recommend a yagi ????

 

I did a test from my work address 200M from the transmitter and it still recommends a phase array!
there is so much signal I can plug in a coax fly lead into the tv with the other end open and tune in :)





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Ultimate Geek
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  Reply # 1474974 19-Jan-2016 22:36
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Athlonite: You would get away with it if your roof was concrete tile not so sure about colour steel metal seems to block signals quite well even with a high gain antenna the other thing you'll need to watch is the power of the signal at the box you wish to plug it into you may need to plug in an attenuator between the end of the cable and the box,  atleast when I was installing sky that's what we were told to do as it can cause the tuner to burn out   

 

Ha ha, The only way to burn the tuner is if it was struck by lightning.

 

The tuner has AGC ( Automatic Gain Control ) it will dial back the signal strength to accommodate strong signals, when it gets too much the front end of the tuner will overload and you will have similar issues to not enough signal ( In the analogue world, not sure about digital )

 

If you have one end of the roof that is not steel and it points to the transmitter use that one.

 

Looking at the LOS predictions Waitarua gives the better result, just use the 43element.

 

UHF can be a fickle beast and I have seen it more than once that raising and lowering the antenna can improve signal strength amazingly.

 

Good luck but I would recommend an aerial installer that has a decent signal strength meter to get the best result for you.

 

 

 

John





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  Reply # 1474985 19-Jan-2016 23:01
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rh2600:

 

Yeah good point about the size, I might wind up assembling it up there!

 

Another quick question - I seem to have a mix of neighbours pointing to Waiatarua and the Sky Tower.

 

Also I notice there is some differences in the channel frequencies between the two towers, do both broadcast all the same channels?

 

 

I'd go for a 43 element or phased array outside. Any indoor antenna can be a real pain, particularly under a steel roof. SkyTower is very low power compared to Waiatarua. Also it's vertical not horizontal polarisation. Auckland's infill transmitters have different frequencies to Waiatarua and there may be a couple of extra Asian channels still at SkyTower. Used to be several a few years ago. Otherwise channel lineup on all the local Transmitters are the same. I recently setup my Sister-in-law's new TV just near you. She has an old VHF antenna with an old Sky UHF 43 el antenna (horizontal) above it connected with a diplexer. Autotune found all channels at Waiatarua (didn't find SkyTower) with no problems even though I suspected I may have had to remove the VHF Antenna.


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Ultimate Geek
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  Reply # 1474986 19-Jan-2016 23:08
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rh2600: ...put the antenna in the roof cavity (colour-steel roof), ...

 

That's what I did: 91-element pointing (at Kaukau) through gable under steel tile roof. Connected to several TVs so that benefits from a few extra dB. Better to have more elements to give sharper beam - not so necessary with digital perhaps since analogue ghosting not a problem, but may give a better quality digital signal by avoiding multi-path phase distortion etc). Checked that each TV receiving signal near (say 80-90%) but not at 100% to avoid overloading. Can buy fixed attenuation cable inserts of various losses to achieve that at each TV.




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Wannabe Geek
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  Reply # 1679227 29-Nov-2016 08:52
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An update: I finally got round to putting a phased array in the roof cavity.

 

So I went ahead with a phased array, mounted it inside the roof but right at the outward face of the roof and turned it to point generally in the direction of Waiatarua.

 

Even just by eyeballing it off the matchmaster map - it's working great! I've got about 92% signal strength and all channels working perfectly.

 

Was so happy I gleefully tore down the satellite dish on the outside of the house - those things are bigger and heavier when you get up close on a high ladder!


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