Re: Joining co-axial cable outdoors

[Peter Crosland]

You cannot just join it electrically, the impedance must be maintained. You could fit connectors and then seal it all with self-amalgamating tape. Unless it is a very long run the best solution is to replace the cable. If it is more than five years old it is probable that it will have deteriorated enough to reduce the signal significantly.

Joining co-axial cable outdoors - what's the best way to do it? > I've got an aerial cable running along the outside of the house wall > and I want to splice in an extra length. > Would soldering be best? > And how would it be done neatly? > -- > Chris

[mike ring]

Chris wrote in news:OT4KVJAouWW$EwVX@[127.0.0.1]:

I agree with Peter, unless, there are compelling reasons against, replace the whole lead with quality coax -it's the second most important bit of your telly - the aerial is the first. You will lose about half the signal in two joints to fit plugs, needed to introduce a coupler.

Having said that, I would try neatly soldering it, keeping the shape as much as possible, as I think it would be lees worse than 2 joints + a coupler.

I would do it in a small diecast box, waterproofed by all available means, grommets, etc.

mike r

[mike ring]

Dave Plowman wrote in news: [e-mail]:

Flying foxes?

and I jointed it with normal Belling

Lucky od sod, I used to live in a wet string area, but now I need something like Goonhilly, but I'm still defeated by cochannel from across the channel on fine summer evenings

And now ***** Sky is taking away channels 3, 4, and 5 unless I subscribe, I didn't think that was legal, and freeview piillates and locks solid, usually in the middle of a recording.

BTW, are the modern boxes any better than my Philips Ondigital? Apart from the locking up it produces LF audio which is annoying through my audio system (but inaudible on the telly speakers

mike r

>

[Martin Pickering {UK}]

The problem with joining cables is not signal loss but signal reflection at the joint. This can be a disaster for digital signals.

See

[James Hart]

The newer boxes are a world apart from the older ondigital ones. I've got both an old Philips which is now only used for radio and a newer Daewoo, which is rock solid. The Setpal tuner in the Daewoo can be found in several others as well, usually around £70 upwards.

[Dave Plowman]

No - the aerial cables come down the side wall and into the cellar via an air brick. And a dying fox decided to chew them as a final act before popping his clogs.

Yes.

I've not had this trouble with mine, and have in fact relegated it to an audio only device. It used to cause the most amazing splats on TV audio when it locked up, though, but doesn't lock up on sound only stuff. At the moment, the bitrates off Freeview are rather better for radio than DAB. But I'm sure they'll find a way of worsening them soon.

[Dave Plowman]

Hence the need for a properly made joint.

[mike ring]

Dave Plowman wrote in news: [e-mail]:

It used to cause the most amazing splats on TV

That's a point, the sound never locks

Any suggestions as to boxes - Argos have a nice selection, but they are not covered by the return guarantee, which makes me think it's still a big gamble

mike r

[Owain]

"mike ring" wrote | Any suggestions as to boxes - Argos have a nice selection, but they | are not covered by the return guarantee, which makes me think it's | still a big gamble

QVC home shopping often have DTT boxes and they have a 30 day no quibble money back guarantee, which gives you plenty of time for fiddling with the aerial. Okay, so you can't get QVC without a box, but try

occasionally or phone [phone]

Richer Sounds have a Thomson box for twenty quid with any plasma screen :-) Or a Goodmans at £70 or Thomson at £80

Owain

[Chris]

In article , mike ring writes

One thing that may help - it's a radio FM aerial - not a telly. I can' t easily get to the aerial to replace the whole wire - it's very high - and I'm frightened of high ladder work. Haven't heard of "self-amalgamating tape", which sounds interesting.

[The Natural Philosopher]

True if pedantically interpreted, but untrue in practice.

To join coax the procvess is as fillows.

First of all stribp backl the outer insulation, then fold back the braiding and get it out of the way to expoose the inner isnulation.

Strip about half an inch of that on each cable.

Now slip some BIG heatshrink tubin over one of the cables outers, and another smaller diameter bit over the inner insulators.

Solder the inner conductors together by laying them parallel and flooding with solder.

Pull the heatshrink over the inner and seal down with ahirdryer/heta gun etc.

Thats teh conductor done, and insulated

Now pull the braids together and just solder em someohow to make a connection. needent't be perfect.

Now get some aluminium foil and wrap teh lot with a thin layer of that. Don't try and solder it. It won't.

Silde the big heatshrink tubing over he joint, slap some silicone sealer or epoxy resin inside and seal with heatgun.

If you are really worried about corrosion, wrap the whole thing in a few layes of cloth soaked in silicone :)

VSWR won't be exactly 1, but will be better than most plugs and sockets :-)

[The Natural Philosopher]

A well made joint will be less than a couple of connectors.

[PoP]

Could you qualify your response please?

When I studied for my HNC Electronics at college we specifically looked at this issue, and RFI signal degradation was certainly a result - trying to tap into a wire (or split it to go in two different directions) would invariably introduce harmonics and reflection - otherwise known as distortion - into the signal because you had an improperly terminated circuit. Now whether or not this might impact the TV or radio you are feeding is another matter, but the degradation was very real.

Naturally I will bow to your higher level of intelligence if you can provide some alternative suggestions which are backed by fact.

PoP

[Chris]

In article , PoP writes

All I'm trying to do is to make the aerial longer, without high ladder work. I'm not splitting it. I just want it to go to a room further away from the aerial on the roof. And - it's FM radio - if that makes a difference.

[PoP]

That wouldn't be a problem - I misread the word "splice" to mean that you wanted to create a tee junction to split the signal.

Not really.

Easiest way is probably to get an inline plug/socket for the aerial lead, do the join, then wrap it thoroughly with self-amalgamating tape as others have suggested.

If you attempt to solder the lengths together you might (and most likely will) create a source of interference. Aerial cables carrying RF signals are co-axial, and to perform the solder work you'd have to break thru the outer circuit to get at the central core. This would disturb the impedance of the cable.

But possibly not enough to be noticable.

PoP

[Frank]

So just order it from argos via the net or by phone then your still get 7 days to return it

[Dave Plowman]

Teeing off is a rather different matter than jointing a cable. For a start, if you're feeding two destinations, you'll get a double termination unless it's done correctly.

[The Natural Philosopher]

We are not I believe talking about splitting it or tapping into it. we are talking about joining it. A solder joint as I described is usually better than a plug and socket.

Only a dozen years as a prtacticisng electronic engineer and an MA in the subject I am afraid.

[The Natural Philosopher]

Not much difference.

The issue is, as has been pedantically stated, one of reflection. This may set up resonances in teh stubs to each side of teh joint, so that some stations arer stronger, othgers weaker, depending on frequency.

However we used to join cables a lot in test situations, and the VSWR was never high enough to be a significant problem.

Do it, and if its seriously s**te you can blame me and do the job 'properly'. But you won't need to.

[PoP]

???

If I was wrong in what I said previously then I'm always happy to concede. However, as it happens I stand 100% behind what I said previously, and await with some patience you revealing what your facts are based upon.

Very helpful. There's clearly distance between our methods. One is to do the job properly, the other is to bodge it. Must be bodge-a-job week I guess :)

PoP