[rai uno]

It is such an unseasonably nice day oop here that I thought I'd get around to re-cabling my 80cm Motorised Dish.

Very glad to report approx. 10% increase in Signal Strength across the board.

Perhaps a salutary reminder to even the most committed of hobbyists that "stuff degrades" with time.

[billnot]

Good reminder, Rai, but here you're preaching to the enlightened. Would you like to come and tell some of my clients that if they renew their LNB and cable their fringe reception will improve?

I reckon new cable every 5 years - how old was yours?

[rai uno]

Originally Posted by billnot

Good reminder, Rai, but here you're preaching to the enlightened. Would you like to come and tell some of my clients that if they renew their LNB and cable their fringe reception will improve?

I reckon new cable every 5 years - how old was yours?

About 5 years ...........

I can get a few Channels from Amos again, which is my personal "System Performance Test".

I'd willingly join your business (in preaching mode) should circumstances ever permit

[wod1]

good post i think i need a new lnb as getting some wierd picture breakup. i would be watching a channel picture all fine and then randomly their is some picture breakup for a second or so in the middle of screen like it would pause for a second

no need for new cable here as using a year old run of wf125 so thats fine, what cable do you use rai ?

time for the 4 core cable on the actuator to get it moving

[Geoff274544]

My old 80 cm dish had the cable running along the plastic guttering and I mean inside the guttering.

[Geoff274544]

Originally Posted by rai uno

About 5 years ...........

I can get a few Channels from Amos again, which is my personal "System Performance Test".

I'd willingly join your business (in preaching mode) should circumstances ever permit

Extreme Satellite Makeover. How about it Rai Uno? You could replace cables, boxes, dishes. We will take you to a desperate family in each show. Got no cash? Rai Uno will hook you up to FTA Satellite.

[wod1]

as you changed the cable, did you change the lnb as they are known to degrade after a while

which dish do you use now then the large one in the garden ?

[Justin Aerial]

Originally Posted by billnot

Good reminder, Rai, but here you're preaching to the enlightened. Would you like to come and tell some of my clients that if they renew their LNB and cable their fringe reception will improve?

I reckon new cable every 5 years - how old was yours?

Are you suggesting that cable only lasts 5 years ?
Assuming that it isn`t damaged (for example by rubbing against the roof) I don`t agree with that at all.
The worst environment for a cable would be on a South facing roof where it`s exposed to maximum sunlight, but even there it should last far longer than 5 years, at least 10 and possibly 20 or more.
If it`s clipped to a wall, especially a North facing wall, it should last even longer than that.
My own cable is on a South facing roof, it`s been up nearly 10 years and it`s still in perfect condition.

Having said all of the above, decent cable, in good condition, is very important to any installation. Just as important as the aerial, possibly more so ?

[sat12345]

Yes it works, the point is it works better

[Sam Radford.]

Originally Posted by Justin Aerial

Are you suggesting that cable only lasts 5 years ?

The way I read it, he's suggesting (and proved by measurement) that, for satellite TV using frequencies from 950MHz to more than 2GHz, his cable deteriorated outdoors such that the attenuation increased by a measurable amount.

If you are dealing with UHF terrestrial TV, with frequencies below 950MHz, the problem is likely to be far less evident.

I have seen cable that has deteriorated in sunlight. The surface of the PVC looks like crazy paving under a magnifying lens and has presumably become porous.

Another possible effect is that the cable copper core and screen are no longer concentric at bends and under clips, as the core gradually pushes its way into the dielectric, when it's hot and soft in bright summer sunshine, like a wire cutting cheese.

This is guesswork but the visible effect that can be measured is a decrease in signal.

Anyone suffering signal loss should run a temporary new length of LNB cable alongside the old to see if it makes a difference. I expect there will be instances where it will and instances where it won't. If it does, remove the old cable and clip up the new.

[The Skyman]

here in the s of france the cable degrades amazingly quickly.. 5 years is probably when it starts to crack at bends in full sunlight!!
i am now using a Black Cable with a much harder outer plastic and will be interested to see if this lasts longer...anyone any experience with this type of cable.
cheers
the skyman

[Justin Aerial]

Originally Posted by Sam Radford.

The way I read it, he's suggesting (and proved by measurement) that, for satellite TV using frequencies from 950MHz to more than 2GHz, his cable deteriorated outdoors such that the attenuation increased by a measurable amount.

If you are dealing with UHF terrestrial TV, with frequencies below 950MHz, the problem is likely to be far less evident.

I have seen cable that has deteriorated in sunlight. The surface of the PVC looks like crazy paving under a magnifying lens and has presumably become porous.

Another possible effect is that the cable copper core and screen are no longer concentric at bends and under clips, as the core gradually pushes its way into the dielectric, when it's hot and soft in bright summer sunshine, like a wire cutting cheese.

This is guesswork but the visible effect that can be measured is a decrease in signal.

Anyone suffering signal loss should run a temporary new length of LNB cable alongside the old to see if it makes a difference. I expect there will be instances where it will and instances where it won't. If it does, remove the old cable and clip up the new.

I would certainly agree with the latter statment, basic fault finding by elimination.

We`ve seen numerous examples of cable that really has badly deteriorated due to weather exposure, and in every case so far it`s been the brown "low loss" cable, and it was probably 20 years old or more. I`m not saying that black cable doesn`t degrade in sunlight, all I`m saying is we`ve yet to go to a job where weather exposure has caused it to fail (as opposed to damage).

We`ve got a Sky dish on our wall at work (I wouldn`t have one at home, I hate Sky too much for that....) and the cable is draped across a flat roof because there`s no other way to get it were we want it. Bad practice but TINA (there is no alternative). It gets frozen in a pool of water in the winter and baked in the summer. It`s been up for nearly 10 years and it still works perfectly even with the signal you get from a poxy little 43cm Sky dish.

[billnot]

Originally Posted by Justin Aerial

Are you suggesting that cable only lasts 5 years ?

What I'm saying is that in a harsh environment, and with long runs (50m plus is far from rare) noticeable deterioration can be measured in a 5 year old cable. A lot depends on cable quality and positioning, but in a fringe area where every little bit matters it is a consideration.

Cables run underground are much less likely to deteriorate than those running along white painted south facing walls.

I have had cables where the outer insulation literally crumbled in my hand.

[Justin Aerial]

Originally Posted by billnot

What I'm saying is that in a harsh environment, and with long runs (50m plus is far from rare) noticeable deterioration can be measured in a 5 year old cable. A lot depends on cable quality and positioning, but in a fringe area where every little bit matters it is a consideration.

Cables run underground are much less likely to deteriorate than those running along white painted south facing walls.

I have had cables where the outer insulation literally crumbled in my hand.

I can`t say we`ve done many 50m cable runs, your neck of the woods must be stinking rich to have houses that big !
I`d have thought that a 10 to 20m cable run would be far more common.

[billnot]

Originally Posted by Justin Aerial

I can`t say we`ve done many 50m cable runs, your neck of the woods must be stinking rich to have houses that big !
I`d have thought that a 10 to 20m cable run would be far more common.

The "stinking rich" (yes there are some) have a dish to themselves. Mere mortals share the cost of a 2,4m dish between them and each has their own cable(s). Runs of 100m (i.e. a single roll of cable) are commonplace; runs of 200m not rare. There is some loss in a 200m run, but it's still better than the alternatives (no BBC or using a dodgy rebroadcaster).

I recabled one such dish only last week; I got through three 100m rolls for the four houses. The longest run was 120m.

We're talking about a 10 ft wide frying pan that has to have a clear line of sight to the satellite (over the whole of its surface) as well as being as discretely placed as possible. You can't put it on the wall with a couple of rawlplugs!

My own dish is clearly visible in Google earth - PM me if you want the reference.

[wod1]

what cable do you use for runs that long, wf125 ? as it cant be the cheap stuff rg6 or ct100 due to the signal losses over that distance.

[billnot]

Originally Posted by wod1

what cable do you use for runs that long, wf125 ? as it cant be the cheap stuff rg6 or ct100 due to the signal losses over that distance.

http://www.demon-multimedia.com/prod...87&ampliada=Si

[wod1]

hmm must be a variant of wf100 then does it have copper foil/braid ?

i guess wf125 would cost too much out in spain for you to use on installs.

[billnot]

Originally Posted by wod1

hmm must be a variant of wf100 then does it have copper foil/braid ?

i guess wf125 would cost too much out in spain for you to use on installs.

Yes, it has copper foil and braid; the cheaper stuff sold by the same dealer is aluminium.

I'm not a great theoretician. Fringe reception frequently doesn't follow any logical pattern. If it works, it works - don't worry about why.

[jeallen01]

Whilst I accept that deterioration of the cable itself is quite likely, it always pays to check the condition of the connections to the F-plugs first! You can get corrosion in these and that will probably cause a lot of signal loss (especially if the installer has been stingy with the sealing) and that is easily corrected.

[Justin Aerial]

I`ve just been up on our flat roof where we store the ladders and I found an offcut of satellite cable laying there.
Both ends were just cut with no sealing whatsoever.
God knows how much rain had washed past it because it must have been up there at least a year. On the exposed ends the copper was all darkened with oxidation and I was interested to see how far down screening this had spread.
I have to tell you that, somewhat surprisingly, only half an inch down it was lovely and shiney......

[Justin Aerial]

Originally Posted by jeallen01

Whilst I accept that deterioration of the cable itself is quite likely, it always pays to check the condition of the connections to the F-plugs first! You can get corrosion in these and that will probably cause a lot of signal loss (especially if the installer has been stingy with the sealing) and that is easily corrected.

Wherever possible weatherproof well ventilated enclosures should be used and under those circumstances no sealing is neccessary. There are even LNBs (certinly usually Quad types) which have a shield which pulls down over the Fs to provide weather protection.

[Sam Radford.]

I always fill outdoor 'F' plugs with silicone grease. That keeps condensation at bay in those pull-down LNB covers.

Air-spaced coax sucks water down the dielectric by capillary action. I've seen it running out the bottom end like a tap! I prefer WF100 "foam" dielectric cable for that reason.

Not much gets down the copper braid unless the PVC sheath has cracked and become porous. Painting exposed cable helps protect it from UV and rain.

[SWIZZ?]

Originally Posted by The Skyman

here in the s of france the cable degrades amazingly quickly.. 5 years is probably when it starts to crack at bends in full sunlight!!
i am now using a Black Cable with a much harder outer plastic and will be interested to see if this lasts longer...anyone any experience with this type of cable.
cheers
the skyman

Sorry to be responding so late, but expats in France may be interested.

I read in an English language newspaper published in France, that only white cables are allowed under French regulations.

Because we were selling our house & the French equivalent of HIPS were due, I changed from 10 year old black cable with copper foil/braid & hollow dielectric to white with Aluminium foil/braid, with foam dielectric (This was the best I could find within 30 km)

The signals dropped by 10 to 15% !

The “Expert” doing the HIPS didnt find the cables!!

There is less radiant heat absorbed by white than black, so it is logical.

Sam R will be releived to hear that the f-plug connections were done with benefit of silicone grease!

David

[Justin Aerial]

Originally Posted by Sam Radford.

I always fill outdoor 'F' plugs with silicone grease. That keeps condensation at bay in those pull-down LNB covers.

Air-spaced coax sucks water down the dielectric by capillary action. I've seen it running out the bottom end like a tap! I prefer WF100 "foam" dielectric cable for that reason.

Not much gets down the copper braid unless the PVC sheath has cracked and become porous. Painting exposed cable helps protect it from UV and rain.

We sometimes get people asking us whether they should use silicone grease on connectors.
Well I have to say I`ve never met an aerial installer who uses it, and that includes those I know do a good job, and I don`t use it either. We`ve never been to a job where use of silicone grease would have prevented the customers problem occurring in the first place. Oxidation between the cable and the connector is not a problem, unless you suffer water coming down the cable. But the latter will also have knackered your cable plus whatever it`s plugged into.
Worrying about oxidation at the connector is like being
concerned over the flat tyre your car`s just suffered whilst
being written off in an accident !
This thing about silicone grease may be a throwback to the
days when Mast Head (outdoor) splitters and amps weren`t drained and ventilated as well as most of them are today, ours certainly are. I can`t honestly see why it should be necessary, other than in a very damp cellar. But if the aforementioned cellar was damp enough to require the use of silicone grease then you shouldn`t be putting anything electrical down there anyway. And if you did the damp would have played havoc with the amp or splitter (that the plug is connected to) long before you should start worrying about the plug !