Weak signal on some channels

[MikeSh]

Chatting to my neighbour today and he mentioned that on his Freesat system (Humax box, 4-5 yo, but don't know which exactly) he can't watch Dave and a few other minor channels because they report weak or low signal. Been happening for a couple of years.
I'm puzzled as I thought all the channels were on the one big 'stream', unlike Freeview where there are different frequencies and powers used for each mux.

Any ideas on this?

 

[MartinLiddle]

Chatting to my neighbour today and he mentioned that on his Freesat system (Humax box, 4-5 yo, but don't know which exactly) he can't watch Dave and a few other minor channels because they report weak or low signal. Been happening for a couple of years.
I'm puzzled as I thought all the channels were on the one big 'stream', unlike Freeview where there are different frequencies and powers used for each mux.

Any ideas on this?

There are a lot of different frequencies plus horizontal and vertical polarisation on satellite channels. It could be an LNB problem or a dish alignment problem or a cabling problem. A starting point in diagnosing the problem would be knowing which channels he can receive and which he can't.

 

[Black Hole]

This might help:

Freesat - Frequency and channel list - Astra 2 UK Spotbeam and Astra 2 European Beam

 

[MikeSh]

Oh crap. I've seriously misunderstood this satellite stuff.
There are actually three satellites providing Freesat?

 

[Black Hole]

There are actually three satellites providing Freesat?

Yes, same ones as Sky and all within the beam width for the dish/LNB (so it's no good thinking a bigger dish is necessarily better). There are at least a couple of reasons for this: capacity and redundancy.

 

[Black Hole]

I thought all the channels were on the one big 'stream'

Maybe you're thinking of cable (optical fibre), where the carrier frequency is hundreds of terahertz rather than a few gigahertz (and therefore has a much greater data bandwidth)? I'm not sure whether Virgin delivers a single carrier or multiple carriers (optical frequencies) to the consumer*, although I know trunk fibre uses optical frequency splitters/combiners to operate multiple carriers over one fibre.

* Actually, I'm not clear whether Virgin delivers the whole payload constantly or just a specific service on demand, but I presume the former.

As an aside: even xDSL (broadband over copper) uses many carrier frequencies and splits the data across multiple channels, adaptively shaped to suit the transmission characteristics.

I've seriously misunderstood this satellite stuff.

So it seems.

 

[MikeSh]

so it's no good thinking a bigger dish is necessarily better

Possibly worse, though I imagine they design them to not have pinpoint focus.
Actually, I recall now that I did know that there were two satellites as is seen references to E & W I think. But three is definitely a new one.

So it seems

We moved into this house with a vacant Sky system. I bought a 1010S, plugged it in and it worked. This is the first time I've really got into the nitty-gritty of how the system works with a view to maintaining/improving or installation.

 

[prpr]

Possibly worse, though I imagine they design them to not have pinpoint focus.

It's nothing to do with focus, as such. Signals effectively arrive from infinity and are focused on to the LNB pickup point by the reflector (dish).
The effective diameter of the dish is the most dominant factor in giving gain, and the inverse applies for defining the beam-width, so larger dish = higher gain and narrower beam-width and smaller dish = lower gain and wider beam-width.
Obviously you need enough gain to give a decent signal out of the noise, and not too much beam-width so as not to pick up signals on the same frequency from adjacent satellites, but enough to allow effectively co-located ones (in practice they are a long way apart) to be received without there being too much pointing loss (i.e. being off-axis).

 

[DaveReading]

Chatting to my neighbour today and he mentioned that on his Freesat system (Humax box, 4-5 yo, but don't know which exactly) he can't watch Dave and a few other minor channels because they report weak or low signal. Been happening for a couple of years.
I'm puzzled as I thought all the channels were on the one big 'stream', unlike Freeview where there are different frequencies and powers used for each mux.

Any ideas on this?

Would I be right in thinking that Drama and Yesterday are among the other channels your neighbour is having problems with ?

 

[MikeSh]

Would I be right in thinking that Drama and Yesterday are among the other channels your neighbour is having problems with ?

I don't know. He said "other minor channels", or words to that effect, so those are quite likely.
I will ask him for more more info, but I don't see him that often.

 

[MikeSh]

so larger dish = higher gain and narrower beam-width and smaller dish = lower gain and wider beam-width.

That's what I was referring to.

 

[Black Hole]

The effective diameter of the dish is the most dominant factor in giving gain, and the inverse applies for defining the beam-width, so larger dish = higher gain and narrower beam-width and smaller dish = lower gain and wider beam-width.

I imagine the LNB has an "acceptance angle" which would impose an aperture stop regardless of how large the dish was.

 

[Rodders53]

I'm not sure whether Virgin delivers a single carrier or multiple carriers (optical frequencies) to the consumer*,

* Actually, I'm not clear whether Virgin delivers the whole payload constantly or just a specific service on demand, but I presume the former.

Multiple mutiplexed DVB-C frequencies:
https://www.digitalbitrate.com/dtv.php?lang=en&liste=2&live=209 has some of them.

The equivalent for UK D-Sat is https://www.digitalbitrate.com/dtv.php?live=69&mux=11954&liste=2&lang=en
and there's also UK terrestrial there.

-------------------- back on topic---
Dave is on 12.129GHz, Vertical = 13 Volts (V) and 22kHz tone (Hi band) from the receiver tuner to the LNB to switch mode ...

Humax tend to have signal Diagnostics readouts... use it on the neighbours system when tuned to different TV channels?

 

[MikeSh]

Dave is on 12.129GHz, Vertical = 13 Volts (V) and 22kHz tone (Hi band) from the receiver tuner to the LNB to switch mode ...

Are those frequency blocks transmitted at different powers (like Freeview muxes are)?

Humax tend to have signal Diagnostics readouts... use it on the neighbours system when tuned to different TV channels?

I need to talk to him again. I think he said it's been like this for a few years, so it's possible be won't want to do much. But he works in engineering, so might be prepared to give it a go.

 

[Rodders53]

Are those frequency blocks transmitted at different powers (like Freeview muxes are)?

Yes, but more importantly the transponders have different radiation patterns. Most FTA UK ones are on UK spot beams.
https://www.satandpcguy.com/uk-tv-a...-satellite/astra-2e-satellite-footprint-maps/ is an example Google result that may help inform you?

Usually the 'received' and 'not received' TV channels when compared to the frequency/polarisation of the transponders will have a pattern related to one (or more) of the 4 LNB modes due to a fault... Sometimes it can be down to poor dish alignment... but it needs considered thinking if the dish is not easily / safely accessible.

 

[MikeSh]

It's been a while but I had a chat with the neighbour again yesterday. They actually have a quad LNB feeding two separate boxes, so 2x2 cables, and the weak signal occurs on both boxes. I'd think that means it's almost certainly a dish or LNB issue.

He's going to check more on the box models and which channels are missing, then either let me know to post up, or he may join the forum and do it himself. (I'm going to send him a link to this thread.)

 

[prpr]

My money's on the dish being off-pan. One presumes the obviously obstructed path has been checked and ruled out.

 

[DaveReading]

There was a post on the local neighbourhood group in my area a couple of weeks ago from someone who couldn't receive channels in the Dave/Drama/Yesterday group (hi-band/V).

The problem disappeared when he had his dish alignment tweaked.