Sat signal loss until reboot

[alan]

Probably not what you want but...

[Windmill]

Not how it works for me. But I don't treat them as expendable, I treat them as unexploded bombs.

I stopped going to the pub 10 years ago; too expensive. And anyway a lot of the people I knew or was related to have 'shuffled off this mortal coil' (Shakespeare obviously was observant about the old gits' gait).

[Windmill]

I should look on wikipedia. Always forget how much info is available on-line nowadays (when you can find it).

[Windmill]

More info at last: Using the remote as you suggested to turn LNB power off then on again restores function just as powering the receiver off then on again does.

I put my trusty old Avo Mk. 8 on the receiver cable without doing this properly (no low pass filter to the meter) but the receiver continued to work anyway, as sometimes happens when you ignore what should really be done.

I saw 12.5 volts going up to the roof, and no change in DC voltage when things repeatedly stopped working during some rainy gusts. Later (did I change the channel? Didn't think so, but maybe I must have done) I saw 19.5 volts, and no more failures although the rain and wind has died down.

It's still working, which is annoying because I've done nothing to fix whatever is wrong, so it must still be wrong. Maybe it'll fail again during the next gale.

Seems likely that I really should remake all the F connector connections when I can next get up on the roof.

Was unhappy to discover when hooking up the Avo that not only does the cable have just copper-coated-steel inner conductor, but that the outer braid over the foil can't be soldered because it is (I think) aluminium braid. Which sounds to me like an accident waiting to happen.

[Dave Liquorice]

That is normal, the voltage sent to the LNB determines which polarity signal to receive. The lower being vertical. Curiously I thought the "acceptable ranges" where 12.5 to 14.5 V and 15.5 to 18 V.

Hum, see recent thread about CCS phone cable. It has a significantly higher resistance than copper, like about 7 times higher. If the cable is long there could be an appreciable voltage drop across it. Current is probably 100 mA or more depending on the LNB.

One wouldn't normally solder F-types, they either screw on, crimp or have a compression fitting.

You can't beat copper (well silver probably would but...)

[tony sayer]

I think you'll find most all the cable TV nets in the UK use ally foil cables there not quite as bad as you might think terminated properly..

[Windmill]

Quite likely it will be 16 when it gets through a demultiplexer then 25 meters of cable then a multiplexer then the motor, before reaching the LNB. In fact I had wondered if voltage drop was the cause of the problem, but that doesn't easily explain the 'works for days / fails every few minutes' scenario I'm seeing.

Plus 300 mA if the motor is turning, but of course then the LNB is less relevant.

No, I meant that, so as to get access to the centre conductor, I had cut in half a short piece of cable with an F connector on one end and a connector plus F-to-F adaptor on the other, then tried to solder the two braids together again. I should have explained properly. The centre conductors soldered easily, but for the braid I had to use a little 2 A. terminal block. It still gave the receiver an adequate signal, though I would not have been surprised if it hadn't.

I remember radar stuff which used a lot of silver, and even rhodium.

[Windmill]

Yebbut this wasn't just aluminium foil; the braid was also aluminium and so wouldn't solder. Re-checking the cable specs, I see that it does say 'aluminium wire braid over foil'. Either I didn't spot that, or they've produced a more detailed description in the years since I ordered the reel of cable.

[tony sayer]

Invariably they crimp that sort of cable. You can use screw on F types with it.

I don't think theres a soldered connection most anywhere in the local cable network!..

[Windmill]

I'm now thinking that the cause of my problems may well be that it's difficult to get a good connection to aluminium. A terrestrial antenna usually won't need power, so this stuff might be fine for that, but dish motor and LNB could take going on for 1/2 amp.

This is another case of 'what I think I know is now wrong'.

Once upon a time, RG6 cable had copper inner conductor and tinned copper braid outer, and that's what I thought I was ordering. But this junk has copper-coated steel inner conductor and aluminium foil outer with aluminium braid wire over that.

Maybe there's still some hope, though, short of replacing all the cable.

You say that screw-on F type connectors can be used with it. Is there some special approved method of making the connection? Maybe folding back the foil as well as the braid over the outer insulation, instead of remving the foil and leaving only the braid as I did, and then screwing a suitable-sized connector over that?

[Dave Liquorice]

There may be something in one of Mr Wrights articles, I'd be surprised if there wasn't:

I remove the foil fold back the braid evenly, trim the inner insulation with a sharp blade soit's smooth, sqaure and projects about 1 mm beyond the folded back braid. Screw on the connector until the inner insulation is firmly against the flange in the connector.

F-types outside need to be completely wrapped in self amalgamating tape once mated, they are not damp proof let alone weather proof!

[tony sayer]

Well if you saw the crimp connectors they use;!..

Well if you have a duff connection then you have a duff connection, have a look at the joints in the system and make sure there're well wrapped in self welding tape! and theres no water ingress anywhere along the cables if the outer sheathing has been damaged or slit etc....

You can do that, have a practice:)..

[Windmill]

Don't know why, but looking on Wikipedia is often thelast thing that occurs to me. When finally I did, I found out that the oscillator was somethoing called a 'dielectric oscillator', not a transistor at all. Now I suppose I need to look that up in turn.

That's what I thought, and seemingly that was once the case (which maybe explains those LNBs whose spec gives an operating lifetime for the number of polarisation changes) but according to Wikipedia they now just use two probes at right angles, one to receive the horizontal signals and one to recive the vertical, with the switching presumably being done by choosing which probe you want to take the signal from.

Seems that the protocol modulates the 22KHz tone (on and off in a binary pattern, I think I now remember seeing) to tell which switch what to do.

I'm learning - trouble is I'm forgetting almost as fast!

[Windmill]

IIRC the specs say 3 watts of RF, which is apparently the maximum allowable under EU rules for a dish of 1 metre or was it 85 cm., unless the site has a special licence to operate at higher powers.

Maybe it is 350W ERP, but the field intensities in the largish beam can't be all that high. Calling it 350 watts makes it sound alarming, but what would it be in the beam of a 5 megawatt radar (pulsed, of course)? It would be something horrendous, but there used to be jokes (I *think* they were jokes) about guys who temporarily sterilised themselves by standing in the beam for a few seconds.

[Windmill]

Doesn't seem to. In fact the behaviour is becoming more random all the time. It has worked steadily for about 30 hours now.

That could well be a part of the problem, but when I can next negotiate with the upstairs neighbour I've decided to replace at least the LNB to motor and the motor to multiplexer cables with real copper 125 cable instead of the aluminium braid wire on the so-called RG6. Yuck!

[Windmill]

I need to have a look. Using a different PC.

That's roughly what I did. But the crappy coax I bought has just a few strands of aluminium braid which makes me wonder about the quality of the contact with the F plug body.

I used silicone rubber sealant on most of the connections, but there were a couple where I didn't (because I needed to muck about with a satellite meter aligning on the satellite, and thought I might need to repeat the process).

However the setup, which worked initially (months ago), failed before it rained, and has behaved oddly ever since. Right now it's been in a working state for hours, but may fail during the next gale.

I lost my self-amalgamating tape (read: put it in a safe? place) but now have more, so when I get the chance I'll use that on the new interconnections I plan to make.

Going to have to find my birth certificate; the TV licencing people claim to be unable to verify my age by contacting the DWP with my NI number, and I don't want them on my top :-)