Tech: Dire problem, co-ax cable, Help please!

Subject: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 25 Jun 10 - 12:50 PM

We now have no TV, which to me is fine but I'm getting it in the neck from my boy, Danny 'cos he can't watch his programmes on the main telly.

We have one in the kitchen which runs off a splitter box/booster from the main ariel and through a set top box for freeview, this works fine. The same setup for the main telly, but the ariel cable was the old cable from the original ariel that I put from the splitter box to the set, through the set top box for Freeview, the picture on this telly keeps breaking up whereas the kitchen one was fine but I had put new co-ax cable on that one, so in my wisdom I decided that new co-ax cable from the box to the main telly would cure the problem.

So, purchased the cable and plugs and replaced the old cable, result NO SIGNAL message. I have scoured the net all day to try to find an answer but no luck, so I am hoping like hell that there is an ariel expert out there who can help and save me from a fate worse than death.

The only difference I can see from the old cable is that the new stuff has a foil layer under the copper wire layer. It is RG6 Satellite and TV co-axial cable so it is supposed to be the right stuff. I have fitted literally hundreds of co-ax plugs/connectors in my lifetime with no problems, which is why I am so stumped with this.
Can it be anything to do with the Foil shield?


Please, please, help.

whb

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: a gud ole bwoy
Date: 25 Jun 10 - 01:22 PM

With fear and trepidation I answer your question, because there is always some smarty alec, with more brains, just waiting to rip your ideas to shreds, but here goes.
It could be due to the ohm rating of the new cable, ie the new cable has what might be thought of as more signal resistance. Therefore weaker signal at TV and poor picture. You could try a signal booster.
Another fix, which even an ex Granada engineer could not explain, is, if the TV aerial is accessible, remove the shroud side di-pole from the clamping screw and either tape it up or bend it out the way a little so that when it rains water can't bridge the gap. We've had to use both 'fixes' before we could get a good signal.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: a gud ole bwoy
Date: 25 Jun 10 - 01:30 PM

OOps first read the question and then read it again. Having re-read you don't want a booster because you already have one.
Re-think, must be an earth problem 'Another fix' would also cure that, but at the set try cutting back the foil and the copper shroud so that its not contacted by the co-ax plug.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 25 Jun 10 - 01:31 PM

Thanks for the quick reply, but it is attached to a booster/splitter box as was the old cable

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 25 Jun 10 - 01:35 PM

Messages must have crossed but I will try your suggestion, do I read it correctly, and you mean I should not let the copper wire and metal foil touch the plug at all? just at the set end.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: pdq
Date: 25 Jun 10 - 01:46 PM

You might try testing each cable you made on a simple system, one without boosters and splitters.

You might even consider taking them to a neighbor's house and testings the one at a time.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 25 Jun 10 - 01:49 PM

I already tried the new cable straight from the ariel, bypassing the booster box! No joy.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: a gud ole bwoy
Date: 25 Jun 10 - 03:16 PM

It doesn't matter but leaving the arial end as is and not letting the copper and foil touch the co-ax plug at the set end is the easy option.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: Simon G
Date: 25 Jun 10 - 03:28 PM

Perhaps its a faulty cable - has a break in it

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 25 Jun 10 - 03:34 PM

A Good Quality Low Loss 75 ohm RG6U Specification Co-axial Cable, Foam dielectric construction with copper braid and foil shielding. 6.4 mm diameter.

1mm solid copper conductor
64 x 0.12mm bare copper braid
I am totally flummoxed! I tested the wire by putting a circuit tester on each end and the inner core shew ok and so did the outer layers so the cable isn't broken and there is a circuit. So why is the signal not going from the booster to the set.

I've put the specs for the cable here in case someone understands them, 'cos I certainly don't. Maybe that's where the problem is, although it is supposed to be ideal for ariel down lead


Foam dielectric
Aluminium foil shielding
PVC Sheath
Overall diameter 6.4mm
Nominal attenuation @ 1000MHz = 20.82dB
75 Ohm
Suitable for digital and analogue reception of Satellite, Cable, Freeview, DAB Digital Radio & much more!

RG6U cable is also suitable for use as a high quality low loss TV aerial down lead and use in multi point systems and extensions. Also suitable for cable broadband and cable TV extensions.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: Effsee
Date: 25 Jun 10 - 03:45 PM

I don't suppose your Freview box/handset has a DTV/analog switch/button on it?

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: John J
Date: 25 Jun 10 - 03:46 PM

Do some basic conductivity tests on the cables - although you'll need a multi-meter for this:

1) Check there is NO conductivity between inner and outer conductors of the coax. Conductivity = short circuit = no signal

2) Check for continuity on all cables - both inner and outer (separately of course!). You should have good conductivity = zero ohms.

3) Check continuity between the TV end of the cable and the aerial end of the cable. Important: disconnect the cable from the aerial before you do this.

That should give you a clue.

JJ

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 25 Jun 10 - 05:14 PM

Effsee, no switch,

JJ, I wish I could, but I really haven't got a clue as regards ohms, and wouldn't know how to operate a multi-meter, unfortunately.

I just cannot understand why one I did is working perfectly, and the other which I did EXACTLY the same in every detail (apart from having foil in one cable and not the other) will not work.

Looks like I will have to get an engineer in at an exhorbitant rate.

Thanks for all the suggestions anyway, much appreciated.

whb

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: John J
Date: 25 Jun 10 - 07:38 PM

Where are you located?

Do you know any local radio amateurs (hams)? They may well be able to help checking your cables out, it would (should!) be a simple job for a ham.

If you're anywhere near local to me (south Manchester, NW England) I would be happy to help.

Cheers,

John

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: Leadfingers
Date: 25 Jun 10 - 08:18 PM

Maplins do Multieters for only a few quid and they are dead easy to use - Select low Ohms range to check continuity, and a fairly high ohms range to make sure there isnt any connectivity between the inner and the shield ! I am West London if I can help !

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: The Fooles Troupe
Date: 25 Jun 10 - 09:18 PM

John J's suggestions were exactly mine.

If no multimeter, you can use a battery, appropriate voltage torch bulb and bits of spare wire - check that you get a circuit - bulb lights, before trying to test the cable. Then try John's suggestions, most especially that the inner core is not shorted to the shielding - this will 'short circuit' and you will get no signal out of the cable. Been there, done that, recently!

It doesn't really matter what sort of temporary kludge mess you put together, as long as the bulb lights when you test it first (and you do not use the wrong bulb, so it blows!) - if you use a new style 'led' light, not an old 'incandescent' bulb, they only work one way! :-)

You could try taking the unplugged cable to a place that will check it (and maybe redo the ends) for you. You can crush the shielding with certain types of plugs, if you do things too tight - been there, done that too recently!

RG6U cable should be OK - but it depends on the length of run - you always get a loss for each metre - and if it's a long run you may need a higher grade cable. How long is the cable you made? Also if the down run cable from the antenna is old cable, it may be losing signal too, and may need replacing.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: The Fooles Troupe
Date: 25 Jun 10 - 09:40 PM

To explain
Nominal attenuation @ 1000MHz = 20.82dB

The lower that number, the less loss and the higher grade (also expensive) the cable. 3 dB means that you lose a barely noticeable amount, 10 dB means that you lose 1/2 the power. The dB scale is logarithmic - so each dB is 10 times the power of the previous. If you have a low or bad signal - old aerial/cable downlink you may not have enough signal at the end of a very long run for a digital signal - but I'd first suspect the cable not put together correctly.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 26 Jun 10 - 03:33 AM

What wonderful people, thanks so much for the offers of help, unfortunately I am in Suffolk (the sticks) which is way out.

Now I will have fun trying the techniques suggested, I like the Foolestroupe one with wire and battery etc, so I'll start with that.

whb

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 26 Jun 10 - 03:38 AM

Sorry, forgot to mention that it is quite a long run approx 9 metres, but as I said the other telly with exactly the same run and setup works fine???? BUT, different cable, so maybe it would pay (if all else fails) to get another cable the same and try that...ah well!

whb

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: GUEST,JJ
Date: 26 Jun 10 - 04:09 AM

How about testing by substitution?

Try re-using the old cables just to make sure the original set-up still works. It may just be that the digi-box or whatever has failed.

Another possibility - try a re-scan, the digi-box may have lost it's memory.

Do you still have analogue transmissions in your area? Try and receive an analogue signal by wiring the aerial directly to your TV.

Unless you're in an area with particularly poor signal strength you should be able to get some sort of signal using a set-top aerial - although a weak digital signal isn't quite so easy to detect.

Can you borrow another TV to check out on your aerial system?

Again, try the radio amateur route - we're generally a decent lot!

Very good luck...and don't get down-hearted!

John

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 26 Jun 10 - 04:59 AM

JJ, I can,t try the old cable because in my wisdom (pillock that I am) I cut the plugs off to get it out and now it's too short (lol).

I did a re scan and it tried, but after the scan it just comes up with "no signal found check ariel and try again".

I joined the ariel downlead to it and went straight to the tv but still nothing.

The ariel system is working fine on the other two sets we have.

Good idea to try the indoor ariel, we've got one somewhere, I'll give that a go.

And I'll try to contact a local ham to see if they can test the cable.

Thanks again everyone.

whb

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: s&r
Date: 26 Jun 10 - 07:05 AM

Just a point of pedantry:

3db = power ratio of 2:1 (halving or doubling)
10db = power ratio of 10:1

db are sometimes used for voltage or current in which case
6db = 2:1
20db = 10:1

As for the fault it's just guesswork without seeing it. No signal may not mean no signal: it could be inadequate to produce a picture. You could try moving the tv/freeview combination that works to the aerial connection that doesn't.

Stu

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 26 Jun 10 - 05:37 PM

Well don't ask me what I did but IT WORKS!

I tried the earth thing, stripped the outer layers back at the TV end and plugged in, no change, so wired it back up as normal, plugged in and responded to the "check ariel and try again" message, re scanned and BINGO!

Just doesn't make sense, but hey, it works.

Thanks again everyone.

whb

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: John J
Date: 26 Jun 10 - 05:51 PM

Great news - well done!

John

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: Tootler
Date: 27 Jun 10 - 01:49 PM

Glad to see you are up and running again.

Even so, another thought occurred to me. Is your aerial properly aligned? When I first got a digibox, I had to get a new aerial so as to get an adequate signal. Once connected up, I had to align it to ensure decent reception. I did this by standing in the loft and rotating it. My wife and daughter downstairs told me via mobile phone when we had the best picture. Crude but effective.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 28 Jun 10 - 03:29 AM

I did think of that Tootler, we too had a new digital ariel fitted, but since then we have had some real stormy windy weather and I did wonder if perhaps it had moved slightly, but, the other two tellys work perfectly, so I don't think it's that.

However I might get it checked out, unfortunately it is attached to the chimney right in the centre of the roof and I'm getting a bit doddery now to climb onto sloping roofs. lol!

whb

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: JohnInKansas
Date: 28 Jun 10 - 05:21 AM

Wilby -

I can't claim any useful knowledge about the newer cables; but I was curious enough to do a bit of searching.

I found a number of sites claiming that while the RG6 specification defines electrical/signal properties fairly well, it leaves the actual cable construction fairly vague.

Several sites complained that especially since the appearance of double-shielded RG6, many cables from different manufacturers needed special connectors made only by the same manufacturer who made the cable.

The market has apparently "stabilized" the products, so that it is now claimed that a new "universal connector" should work with any RG6 cable; but there were a number of complaints that objected to that belief. The new universal cable apparently accommodates a double-shield automatically(?).

A few commentors asserted that the old connectors were perfectly satisfactory for any RG6 cable, but all such comments ended with "but only if you're a genius like me."

Unfortunately I didn't find consistent enough descriptions of the old versus new-universal connectors to make notes, but my vague recollection is that some may have called them "Type F" vs "Type D." If those don't work, you can try the rest of the alphabet, I suppose.

Based on my (superficial) research, you quite probably used one of the "non-preferred" connectors on your new cable assembly; but experienced an "accidental stroke of genius" akin to the claims of the posters I found on some of those sites when you reassembled the connector after trying the open-shield connection. (Two more miracles and we can begin your confirmation as a saint?)

After my (superficial) search, I can emphatically agree with the implied opinion in your opening post that there is a near total absence of persons capable of writing - especially about simple things - intelligibly. Since Microsoft recently shows irrefutable evidence of trying to hire as many idiots as possible, there might be some hope that they might deplete the density of illiterates writing "technical stuff" (other than at Microsoft) on the web; but I'm not optimistic since the shallow end of the gene pool seems so much more fertile than the rest.

I think I'll look for pre-molded cables - maybe with splice connectors if necessary - for my next improvement(?). Since the useful part of my property isn't much more than 9 meters wide I should face fewer difficulties than you've had(?).

John

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: wilbyhillbilly
Date: 29 Jun 10 - 06:06 AM

John, It's 0500hrs GMT and I've just read your message and it's made my day, I can't stop giggling.

I did indeed find that most sites I looked at for cable had their own connectors which when fitted needed another adapter to make them fit the TV socket, a typical con job, it would seem that the "F" connectors have taken over from the "old" style "D".

Anyway, hoping for two more miracles so I can qualify for sainthood, might be good!

whb

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: bubblyrat
Date: 29 Jun 10 - 06:13 AM

No problemo back in the 'sixties -- Uniradio 67---BNC Connectors--- Simples !!

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: John J
Date: 29 Jun 10 - 06:19 AM

D type connector are more usually used for data, F type connectors are used for RF.

John

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: Tootler
Date: 29 Jun 10 - 11:09 AM

However I might get it checked out, unfortunately it is attached to the chimney right in the centre of the roof and I'm getting a bit doddery now to climb onto sloping roofs. lol!

Advantage of a loft aerial [g]

Seriously if the other tellys were working it does sound as if the aerial itself was OK.

Subject: RE: Tech: Dire problem, co-ax cable, Help please!
From: JohnInKansas
Date: 29 Jun 10 - 01:17 PM

Since the switch to digital in the US, I'm running one TV off an inside antenna. It is, according to the specs, a very good antenna but appears to pick up a rather narrow beam at the digital frequencies I can find.

I get (usually) four of the seven known local channels, but two of those disappear if the wind gets above about 25 mph (which is 80% of the time here), or if it's raining anywhere in the county. The antenna alignment has to be adjusted if the wind direction changes.

Maximum distance to what I think are the nearest relays for the local channels is about 15 miles, but reception is, at best, "poor" on all.

But I do get a strong signal from one analog station from Oklahoma City (180 miles away), now that there's no interference in the analog frequency bands. Unfortunately that channel broadcasts nothing but paid commercials for about 16 hours per day.

I likely will put up an outside or attic antenna eventually; but web searches and calls to local stations and TV sellers gets no information that's really useful for finding equipment that will improve my reception. They all assume you want cable or dish, and the thieves whe push those are supposed to solve all the problems for you.

John