Can the Sun interfere with freeview.?

Forums › Freeview (DVB-T/DVB-S) › Can the Sun interfere with freeview.?

xormin

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Topic # 240945 3-Oct-2018 18:27

I have an ex Sky dish I use to receive Freeview. On some days I can not view some channels, typically TV 1 or 2, sometimes a few others. At these times my freeview box tells me I have no signal strength. I notice this happens in the afternoons/evenings when the sun is about 10 degrees above the horizon. The problem self resolves when the sun gets a bit lower. I live about 46 degrees south.

My question is, is this related to the Sun, or is it just a co incident? if it is Sun related can I do anything to stop it?

DjShadow

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Reply # 2100973 3-Oct-2018 18:47

This happens twice a year when the sun is directly behind the satellite, should not have any effect on DVB-T unless the channel is being fed via satellite

RunningMan

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Reply # 2100979 3-Oct-2018 18:53

The other possibility is it is temperature related - the LNBs on some SKy dishes are pretty old now, and become sensitive to temperature causing the LO frequency to drift. Next time it stops, squirt it with the hose to cool it down and see if that fixes it. If so, replace the LNB.

If the sun is setting and 10 degrees off the horizon, it shouldn't be anywhere near directly behind the satellite.

You could also check the dish alignment as they move over time.

Aredwood

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Reply # 2100981 3-Oct-2018 18:58

Not much you can do if the angle of the sun is close to the angle of the satellite that is used to broadcast Sky. Maybe a much larger dish? As the sun is a source of interference (something that was discovered during WW2 radar expierments).

Otherwise could be the LNBF becoming sensitive to temperature changes. Test by squirting the LNBF with the garden hose next time it stops working.

Brunzy

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Reply # 2100991 3-Oct-2018 19:10

Replace the LNB, its a 10750.
You will need a new throat too

RunningMan

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Reply # 2101003 3-Oct-2018 19:28

Sky LNBs could be either 10750 or 11300. The feedhorn is integral, you don't purchase it separately.

Brunzy

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Reply # 2101284 4-Oct-2018 09:13

They stopped using 11300 years ago, only used on commercial jobs.
If the op buys a single 10750 the throat is incompatible 25mm vs 40 mm

xormin

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Reply # 2110611 18-Oct-2018 18:09

Thanks for all the reply's. Today was the first day with enough sun (had plenty of snow) and sure enough it stopped working again. I hosed the horn down and it started working again. I guess this means it is coozed.

My question is what has failed in the horn, and why does it fail only on TV 1 and 2?

RunningMan

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Reply # 2110613 18-Oct-2018 18:26

Generally it will be a capacitor in the LNB that is sensitive to heat. The local oscillator can't hold the correct frequency, and everything drifts a bit. Due to minor differences in transponders, different groups of channels will have a different threshold that it drops out.

The fix is to replace the LNB on the end of the dish arm. If you can easily post a photo of the dish, we can tell you what to buy.

Jase2985

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Reply # 2110614 18-Oct-2018 18:28

the LNB will have failed, you can purchase a new one to replace it.

and it will be due to the frequency of the signal, will have drifted enough to stop picking those ones up

xormin

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Reply # 2110618 18-Oct-2018 18:48

Here is a photo of the dish.

RunningMan

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Reply # 2110638 18-Oct-2018 19:43

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Perfect. That is one of the Sky dual throat 10750 LNBs. It can be replaced with a standard single throat 10750 LNB. The only issue you may have is as @brunzy pointed out, the neck of those dual LNBs is 25mm, rather than the 40mm diameter of a standard LNB - it means you may have to replace the bracket at the same time.

Here's a couple of options, in no particular order

http://www.freeviewshop.co.nz/noise-10750-band-p-417.html

https://www.trademe.co.nz/electronics-photography/tvs/satellite-receivers/listing-1802622448.htm

https://www.trademe.co.nz/electronics-photography/tvs/satellite-receivers/listing-1805444626.htm

Looking at that photo, it looks like the skew (rotation) of the LNB may be out a little too - you could try loosening the screws on the bracket slightly, and rotating the LNB clockwise a few mm before re tightening. It won't fix a failing LNB, but it may just give it a bit more signal so it doesn't drop out as often.