Humax Foxsat HDR - Picture breakup only on some channels

mlsred

New Member
Hi All,

After some advice...

I'm having issues with some channels on my Foxsat HDR with pixilation and image breakup. The signal and quality indicators fluctuate between 40(ish) percent and 0% on some of the music channels and I get regular "no or bad signal messages".

Things like BBC, ITV, C4 etc are fine, strong 90% to 100% signal/quality.

So I appreciate that this is a process of elimination and could be Dish or LNB alignment/skew and I have an Octo LNB which could be casuing the issue as per this link but I have no idea if my LNB has an amplifier in it or not and if a 6dB In-Line Satellite Attenuator would help?

I did have someone from a satellite/aerial company come out a year or two ago and move my dish onto an arm to elevate it and improve the signal but over the last months I have notice this signal problem which makes me think the dish has either moved or there is an issue with the LNB. I have to say I don't really watch the music channels so it was only when my children started complaining that I noticed the issue but I have no idea how long it has been happening..

I am reluctant to pay for someone to come out and move things around and who will no doubt try to sell me a new LNB, Dish, Extension pole, house (;)) etc..

If I start fiddling with things there is a danger that I will lose all reception but I am willing to give it a go.. Are those satellite meters they sell on ebay and amazon worth the money?

What would be you advice as to the most likely cause? Any suggestions?

Ramble over :D

Thanks
Michael
 

prpr

Well-Known Member
Cause could be almost anything. Here are some things to consider in the fault-finding process:

How big is your dish?
Where in the country are you?
Is it aligned correctly?
Is is obstructed?
Is it damaged?
Does it only do it when it's raining or windy?
Are all of "Lo H", "Lo V", "Hi H", "Hi V" similarly afflicted?
Are all outputs of the LNB similarly afflicted?
What cable do you have between the LNB and the RX?
How long is it?
Is it decent stuff with a proper screen?
Is there any source of interference getting in?
Has water got in?
Are the connectors corroded?
Are the external connectors sealed up with self-amalgamating tape?
Is the LNB duff?
Is the RX duff?

I've never personally used one of those satellite meters as I don't have satellite at home, but some people say they work for them.
And yes, your LNB has a flippin' big amplifier in it. That's the whole point of it - to amplify the signal collected off the dish to a usable level (and to change its frequency) before you lose a load sending it down the cable to the RX. Unlikely that you've got too much signal unless you're on a very short cable.
Dish on an arm to elevate it doesn't sound great, and implies obstruction... or rip-off.

Edit: Added water damage related items.
 
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Trev

The Dumb One
The signal and quality indicators fluctuate between 40(ish) percent and 0% on some of the music channels and I get regular "no or bad signal messages".
Seems like that last thing that you need is an attenuator to make it even smaller.
Dish alignment being slightly out sounds possible to me.
Are all of "Lo H", "Lo V", "Hi H", "Hi V" similarly afflicted?
If you don't know what prpr is talking about, then give us a list of 'good' and 'bad' channel numbers and an expert will work that one out for you' ;=)
As you are getting some channels at 90%/100% a few of prpr's checklist can be discounted for now.
 

grahamlthompson

Well-Known Member
Loss of some transponders can be down to poor water sealing at the lnb and letting water into the coax cable. If you happen to have older CT100 cabling the air spaced dialectric makes an excellent microbore water pipe. If it gets into your satellite box you have trouble with a capital T. The first thing I would do is check the f connectors at the Foxsat end for any sign of water.

There's a list of which channels are high band and low band and horizontal or vertical polarisation here

http://humaxgoodies.weebly.com/freesat-channels-by-transponder.html

Open the file in any web browser.

Changing a lnb is easy provided the dish is easily accessible (Mines 6ft of the deck).

Trev's right the chances of signal overload is miniscule unless you have a very large dish. Most people have a tiny zone 1 Sky dish.
 
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OP
mlsred

mlsred

New Member
Thanks All, a lot to think about, I really appreciate you taking the time to respond

I have a Octo LNB at the moment, although I'm currently only using 4 of the feeds (I was future proofing but haven't really had the need).. can you recommend a good quality Octo or Quad LNB if I do replace it?
 

grahamlthompson

Well-Known Member
Thanks All, a lot to think about, I really appreciate you taking the time to respond

I have a Octo LNB at the moment, although I'm currently only using 4 of the feeds (I was future proofing but haven't really had the need).. can you recommend a good quality Octo or Quad LNB if I do replace it?

If it's a Sky dish there's nothing to choose between them (wider than it's tall). Have a look on e-bay for the cheapest. Note if it's an early Mk1 Sky minidish it's a bodge job to fit a new lnb. Later ones can use adaptors.
 

Trev

The Dumb One
can you recommend a good quality Octo or Quad LNB if I do replace it?
But why would you consider changing the LNB before carrying out a few free and easy tests first? Such as trying to establish whether it is say all High band or say all horizontal channels or all 28.2E or all 28.5E that are giving the problem.
You say you are using 4 of the 8 outputs. OK, 2 for the Foxsat, what do the other two go to? Does this box have the same symptoms? Have you tried the Foxy on the other two cables?
 

prpr

Well-Known Member
Despite asking for advice, some people seem to ignore it and know better, which seems a bit odd. Why bother asking?
It seems he's already made up his mind what the fault is and how to deal with it. You see it all the time with plumbers and such trades. "It must be X, so we'll change it." Then it isn't any better. "Ah, it must be Y, so we'll change it." And so on. They never measure anything or approach problems in a systematic way.
Meanwhile the poor sod paying the bill has to put up with this incompetence.
 
OP
mlsred

mlsred

New Member
One of the potential causes of the problem is the LNB, IF I do decide to replace it once I have looked at some of the other options I was asking for a recommendation on a good quality one..Thanks
 
OP
mlsred

mlsred

New Member
Despite asking for advice, some people seem to ignore it and know better, which seems a bit odd. Why bother asking?
It seems he's already made up his mind what the fault is and how to deal with it. You see it all the time with plumbers and such trades. "It must be X, so we'll change it." Then it isn't any better. "Ah, it must be Y, so we'll change it." And so on. They never measure anything or approach problems in a systematic way.
Meanwhile the poor sod paying the bill has to put up with this incompetence.

"a lot to think about", I really appreciate you taking the time to respond

Not sure how you managed to jump to that conclusion but I hope getting that off your chest made you feel better..Thanks
 

Trev

The Dumb One
The reason for jumping to the conclusion is because several people have made suggestions on possible ways forward for you but you have not really responded to any of them (apart from your thanks) and sort of implied that you are jumping to what is probably the least likely cause of your problem.

GLT made a suggestion for an LNB in his post #6, but if you want to spend money unnecessarily on a 'high quality' LNB for use on a system in which the signal strength is usually more than sufficient for a standard setup, then that's up to you.
 

grahamlthompson

Well-Known Member
The feedhorn shape on a lnb should match the shape of the dish when viewed from the lnb location. Sky dishes have a specific shape so need a lnb designed to recieive signals from the full dish face and not see past the edges is required . If the lnb sees past the dish edges then it can pick up unwanted interference, if not the gain is reduced (which will work but any advantage of a higher quality lnb will most likely be lost). For this reason SKY lnbs have a different collar size to those designed for the normal dish which is slightly higher than wide, so fitting one to a Sky dish requires a non standard adaptor for the larger collar size (These look round to the offset lnb so these have a circular feedhorn, as a result the same lnb can be used on a cassegrain circular dish where the lnb is centrally mounted).

https://www.google.co.uk/search?q=c...oPfoOM%2C_&usg=__uXIE3Bv3aM6DKGnaqvzjix4_8jM=

If you want to use one of the more esoteric designs, you really need to use a dish of the correct shape.
 

Mike0001

Well-Known Member
What would be a reasonable price to pay for an octo LNB then? I see them advertised on Amazon at from £96 down to about £15.
 

grahamlthompson

Well-Known Member
What shape and size is your dish ? The cheap lnbs are likely to be Sky ones which are produced in the millions so they cost very little. The £96.00 one is unlikely to work better than the cheap one. Indeed it would be better to fit a larger dish and a cheap lnb. MK4 Zone 2 dishes and lnb's are available cheaply on e-bay.

Just search for a Zone 2 Mark 4 dish and octo lnb.
 

Black Hole

May contain traces of nut
Speaking as a non-satellite owner, I don't understand this LNB interference business. I can accept that an LNB with a narrow acceptance angle will not get the full benefit of a low f-ratio dish (you could still use a large diameter dish as long as the focal length was long enough), but if the LNB can see past the edges of the dish, would unfocused background microwave radiation really reduce the S/N ratio significantly?
 

grahamlthompson

Well-Known Member
Speaking as a non-satellite owner, I don't understand this LNB interference business. I can accept that an LNB with a narrow acceptance angle will not get the full benefit of a low f-ratio dish (you could still use a large diameter dish as long as the focal length was long enough), but if the LNB can see past the edges of the dish, would unfocused background microwave radiation really reduce the S/N ratio significantly?

What's a low f-ratio dish ? Microwave collection works much the same as optical reflecting telescope technology, the only real difference is that one uses a mirror to reflect light (photons), the other a metallic reflector to reflect microwave energy. If the optical telescope had a receiver (lens/mirror) that collects light beyond the edge of the primary mirror would you expect to see a sharp image. (In this case the unwanted photons come from stray light rather than microwave energy from a similar focussed source)

If you had ever used a satellite box and a dish you would know that you can easily get a strong signal from many locations, and zero signal quality. There's a lot of microwave energy you can detect on a dish, none of which relates to the actual source you want to lock onto. Swing a dish it's not hard to find a near 100% signal source.

Compared to terrestrial we are talking about a minute signal level, satellites do not have the capability to transmit power in the in range required for terrestrial transmitters. They don't need to, consider a terrestrial aerial that can reject signals from a source 22000mls above the equator separated by a small number of degrees.
 
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Black Hole

May contain traces of nut
If you had ever used a satellite box and a dish
Which I have not, and is why I am asking.

What's a low f-ratio dish ?
You drew a parallel with an optical telescope, and telescope mirrors (or lenses) have an f (focal) ratio - which is the focal length divided by the effective aperture. The f-ratio defines the angle of the light cone at the eyepiece (or LNB). I see no reason a satellite dish shouldn't have an f-ratio, or that an LNB shouldn't be specified as having an acceptance angle in terms of f-ratio.

A narrow-acceptance LNB suitable for a small dish with a short focal length would also be suitable for large dish with a commensurately longer focal length, ie having the same f-ratio. Ditto eyepieces for telescopes.

If the optical telescope had a receiver (lens/mirror) that collects light beyond the edge of the primary mirror would you expect to see a sharp image
Yes you would. But the image would be polluted by stray light if any came in from behind the mirror as a general unfocused wash. The image would be degraded, but not eliminated. The question is not what other sources are available if you swing the dish around, but what sources are detected if you swing an LNB around (without the benefit of the dish to amplify and focus the signal).
 

Trev

The Dumb One
Looking around my area, I notice that most dishes are mounted on a brick wall which are not exactly known for their microwave transparency and will surely attenuate any possible microwave interference from behind the dish. Surely even the SKY elliptical dish/LNB throat combination has some 'overspil' as the LNB can't possibly have a cutoff that cuts off exactly at the dish periphery? Not only that, if this were really a major problem, would not the whole dish be skewed, rather than just the LNB. Sewing the LNB must cause more 'overspill' than if it were not skewed? I guess this is done for aesthetic reasons rather than anything else.

As an aside, why does 28.2E have a different skew to its polarisation axis than 28.5E so that a compromise has to be made with dish/LNB skew?

However, I think this thread is drifting off topic, but I also think that there is little else we can suggest to the OP unless he reports back with the results of any tests he has carried out.
 

grahamlthompson

Well-Known Member
See Oval or Round here

http://www.satcure.co.uk/tech/lnb.htm

And more info here

http://www.satcure.co.uk/tech/lnb2.htm

An LNB and feed horn have to be matched to the dish. The open end of the feed horn LNB has to be at the exact focal point of the dish and the horn has to be flared or made with "scalar rings" in such a way that, with it at the focal point, the horn can "see" the exact circular area of the dish - no more and no less. If it is less then it isn't collecting signal from the full area of the dish. If it is more, it is also collecting unwanted "noise" from any warm object (wall), or from the sky, behind the dish.

28.2E uses a non standard skew for it's orbital location. No idea why this is.

An offset dish design avoids the lnb obstructing the signal so improves performance and the more vertical alignment of the dish helps to prevent snow accumulating on the dish. See second link above.
 
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Black Hole

May contain traces of nut
Okay... so warm non-reflective objects radiate significantly (black body radiation) in the satellite TV frequency band? I was aware this is a problem in microwave astronomy (21cm and all that), but...

Thanks for the info.
 
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