Can a TV cable make such a difference?

[GregI]

My family have been using the same TV cables for plugging into the external aeriel on the roof for probably 15-20 years. Our house has 2 aeriels, one for downstairs and one for the upstairs as they are separate buildings but owned by the family.

Recently the 32" TV downstairs was not getting some channels or if it did some of them would get garbage pixels with crackling sound. A high pitched screech is the best I can describe it on channels such as Russia Today (234) and sometimes on channel 32 (Sony Movies).

We thought it might have been the TV so we got a Samsung 43" to replace it and with the same wire it was not finding as many channels as the upstairs TV. For example, Channel 19 (Dave) was missing and channel 32 was not there. Before changing anything the downstairs tv when scanning would find about 130 channels.

We then decided to try the same cable that the upstairs TV has but downstairs and all of a sudden the downstairs TV found over 200 channels, an increase of 70 channels. There was still some pixellation on Russia Today but now channels like Dave and Sony movies was watchable.

I don't know much about analog cables and tv transmission but can a different cable really find 70+ more channels? Would a different cable purchased recently have like more bandwidth or something to accept channels like Russia Today without any picture or sound distortion?

 

[Terminal_Boy]

If the terminals are corroded, have resistive contacts or either of the central conductor or the outer screen are damaged; the old low-tech coaxial TV cable can have wildly varying losses at different frequencies.

Crushing, kinking or stretching RF cables is very bad for them.

 

[varkanoid]

Could even be a slightly loose TV coaxial socket.

 

[lucid]

My family have been using the same TV cables for plugging into the external aeriel on the roof for probably 15-20 years. <snip> </snip>Would a different cable purchased recently have like more bandwidth or something to accept channels like Russia Today without any picture or sound distortion?

There are a few things (potentially) going on with your aerial systems and cables, but Yes, the quality of that short bit of fly lead can make a big difference.

Fly leads with the moulded-on ends can be utter garbage: Poorly made; inadequately shielded; lossy; bad end connections. It's often impossible to tell when the centre pin has broken away from the centre core because everything is encased in plastic, so you end up with a big increase in cable losses. But here's the quirk. At RF frequencies, a broken connection doesn't automatically mean no signal, it might just mean less of it. We know that cables both radiate out interference and act as an aerial to pick up interference. It happens then that a small break such as a solder joint fracture becomes a transmitter and receiver pair for RF. In effect, the signal 'jumps' the gap.

With cables so old, you have the added problem that they may have been made for pre-digital TV use, and so have just one layer of very sparse braid shielding. This was barely acceptable in the days of analogue transmissions. It's totally unsuitable now though. The signals for digital TV are more susceptible to interference, and with all the Wi-Fi, Bluetooth, 2G/3G/4G mobile phone plus all the other sources of signal transmissions and digital signalling (HDMI) and switching noise, there's a lot more interference flying around.

I have a professional TV aerial meter. With it, I can get very accurate readings of signal losses through various devices including cables. I've measured some fly leads in the past and found that they contribute up to 3dB of loss. That number won't mean much, but it equates to 50% of the signal being lost just through a 1.5m-long bit of cable. To put that in to perspective, good quality all-copper TV coax such as WF100 / PF100 / TX100 / NX100 will lose roughly 1.5dB of signal level every 10m. That short and poorly-constructed fly lead could be losing as much as 20m of good coax in just a 1.5m length. That's bad.


Some of the other things going on with your aerial systems are a little more complex to explain, but we're going through a phase right now where TV signals are being shuffled around to make way for selling off some of the airwaves for more mobile phone use. For a lot of people, that means they'll have had to retune a few times as the signals get shuffled down to the lower end of the transmission frequency range. This means that your current aerial might not be such a good match anymore for where the TV transmission frequencies now sit. The result of that could well be a weaker signal.

How this affects you depends on the transmitter you're receiving from, and the type and quality of aerial(s) you have.

Other factors include that some channels are broadcast in groups with higher or lower transmitter wattage. For example, an aerial system picking from Crystal Palace which serves the Greater London area will get most of their stations broadcast at 200,000W, but Russia Today in HD is within a group running at one quarter of that power level. Add this to an older aerial no-longer being a good signal match, and some cable losses could well mean that the TV gets a borderline signal. This might not apply exactly in your case (and particularly not if you're watching RT on channel 234), but it's an example of the cumulative nature of signal losses.

Where the cable is contributing so much in loss that it's tipping the signal over the edge, then I'd say you need to have a look at the signal levels from the aerial system(s) in total. You should have a safety margin of around 15-20dB of additional signal over the point where the TV starts to show signs of signal break up.

 

[Rroff]

At RF frequencies, a broken connection doesn't automatically mean no signal, it might just mean less of it.

I had an interesting one with a headphone amplifier I was making once - forgot to connect up the audio input to one channel and surprisingly it was picking up the audio - albeit much quieter despite a few mm gap (it also resulted in it oscillating until it overheated).

 

[Terminal_Boy]

Au

I had an interesting one with a headphone amplifier I was making once - forgot to connect up the audio input to one channel and surprisingly it was picking up the audio - albeit much quieter despite a few mm gap (it also resulted in it oscillating until it overheated).

Cables can act as antennae when one end isn’t terminated properly. Also, the AF stages in audio equipment have notoriously poor screening, so the amp could have been picking up the leaky AF from the music source. This is also why audio equipment goes Full Metal Mickey when you place an active GSM phone near one.

 

[GregI]

Just an update on this. I have no idea what is going on. If it helps diagnose we are in a town just outside Edinburgh.

A cable was purchased from Tesco. TV scanned in and around 12:30pm every channel was fine. Roll the clock to about 6:30pm and channel 32 (Sony Movies), Russia Today (234) and Tiny Pop (207) were back to their garbly mess. The thing is the HD channels of the BBC (IIRC 101) were absolutely fine and I'm no expert but doesn't getting terrestrial HD mean the cable and TV should be more than adequate? Not getting RT isn't so bad because it has an app to stream the HD channel from internet. We pretty much need Tiny Pop though for our little princess.

Any ideas?

 

[lucid]

Any ideas?

Yes. Start listening to the advice here and stop buying pish aerial cabling from a shop that knows bugger all about the subject LOL

If you bought one of these flyleads from TESCO then you were ripped off royally. Even if it was something 'better' than these, all you really needed was a quid's worth of decent coax and a couple of aerial plugs for something infinitely better.

If it helps diagnose we are in a town just outside Edinburgh.

Well that narrows it down to the better part of 1000 sq kilometres. Thanks

I'm just teasing, but honestly, would you give the AA man such vague info if you were broken down on the drive? No need to answer; it's a rhetorical question.

Edinburgh is covered by two full service transmitters. "Full service" means they transmit the main public service (PSB) stations in SD and HD and all the additional commercial SD and HD stations such as those on the 'local mux'. The other type of transmitters are called relays. These fill in for dead spots in coverage, but transmit a much reduced service known as Freeview Lite. It is based on the PSB channels only. Since you're picking up TinyPop, and that's a station only available on the local mux, then you must be receiving from a main transmitter rather than a relay.

Sony Movies (32) - ARQB COM6
Russia Today (234) - ARQB COM6
Tiny Pop (207) - local mux


Main full service Freeview transmitters around Edinburgh:

Craigkelly - approx 5km SSW of Kircaldy - ARQB COM6 ch37 @ 10kW. 'Local mux' ch32 @ 5kW [NOTES: lots of overlap with Black Hill]

Black Hill - approx 5km E of Airdrie - ARQB COM6 ch47 @ 100kW. 'Local mux' ch30 @ 10kW [NOTES: lots of overlap with Craigkelly]

Technically, Craigkelly is also a relay because it fills in the dead spots where Black Hill doesn't reach. However, it shares the same horizontal polarisation as Black Hill and it carries a full service rather than Freeview Lite.

The nearest other full service transmitter is at Selkirk. However, it doesn't have the power and range to get much past a line running from Lauder to Eyemouth, so you'd have to be a long way south of Edinburgh to get some signal from Selkirk.

Cutting to the chase:
From the limited bit of info you've provided so far it's impossible to make an accurate diagnosis. What we're left with then is best guess based on an incomplete set of data (where you live, how long the aerials have been installed, whether they're old Group aerials, the condition of any cabling, whether there are amplifiers or splitters involved, if there are additional devices such as Freeview PVRs involved, local conditions such as buildings/hills/trees or other obstacles in the way of the signal path - this list is not exhaustive), and so all we can really do is suggest likely causes.

Symptom: sporadic loss of signal day to evening/night
Potential causes: variable signal level because the aerial is getting a marginal signal. This could be because of one or several factors combining; unsuitable aerial / aerial degraded / cable degraded / living in a marginal or overlap area where atmospherics affect signal level, continuing to use unsuitable fly lead / Humax PVR affecting signal level / weak signal overamplified thus reducing signal quality / TV tuner not as sensitive as previous TV model

What to do next?
Stop buggering about tinkering around the edges. If the signal level is wavering in the way you suggest then there's just ONE CURE. Get an aerial guy in to put up a new aerial.

A decent firm will know the local conditions and what type of aerial is best for your area. My best guess for you is that currently a Log Periodic will pick up a broad range of signals and supply sufficient power and quality to drive your TV without signal loss. They'll use a professional digital meter to get the best signal alignment, and then install new all-copper cabling to preserve that signal down to the TV. They should also make up new flyleads for you from the same aerial cable as used for the outdoor installation.

 

[GregI]

If you have any recommendations of what brand of cable/model number that isn't complete garbage that would eliminate the cable as the issue would be good. It seems like a better idea to make sure this isn't the issue before spending hundreds of pounds on a aerial guy.

Apologies for not being more direct about location, I like anonymity but if it helps narrow it down: EH33 1AT

Aerial was installed about 3 years ago for the downstairs.

Just to reiterate, a reputable aerial service will be consulted if a better cable doesn't sort it.

 

[Shmiler]

Probably already been said but if the External aerial hasn’t been changed for years that is probably your culprit.
I Remember when the uk went full digital, we had to change our aerial and also it’s orientation. We had all the problems you do. Glitching, screeching, missing channels. HTH.

just to add I’m EH12.

 

[lucid]

Thanks @Shmiler, looking at the post just before yours it seems that someone at @GregI's home had the aerial changed about 3 years ago.

He didn't say though whether this was a bought-in service or a DIY job. That opens up a whole bunch of extra questions such as what was installed, and whether the installer was competent. I pick up quite a bit of business sorting out previous installers foul-ups. There's this obsession with finding the cheapest installer; and then folk wonder why they need to spend again just a few years down the line. I don't know if that's the case here, but the saying is true: Buy cheap. Buy twice.

 

[lucid]

If you have any recommendations of what brand of cable/model number that isn't complete garbage that would eliminate the cable as the issue would be good.

Hi GregI,
A decent aerial fly lead is what you'd have got from a good local aerial shop. They'd make one for you for about £10 - but I don't know your neighbourhood and if there are still any decent shops left.

There's a very good firm in Sheffield called Aerials & TV. They'll make up leads to order using the same high quality all-copper coax that I use for installations. It's Webro WF100. A 2m fly lead will cost about £7-£8 + del. Not sure what they charge for that though. https://www.aerialsandtv.com/product/attach-plug-to-custom-cable

 

[mmj_uk]

I used cable rated for Virgin Media along with compression connectors and the picture went from breaking up and missing channels to 100% signal quality across the board. So yes, the cable (and connectors) can make a big difference if that's the source of the problem.

Webro WF100 is pure copper so technically it's perfect but I found it too soft and easily damaged (kinked/crushed), the cable I have is copper clad steel from a reputable brand and it's a lot more tough and durable (shield is 60% coverage). What was the cable you purchased from Tesco?

 

[GregI]

Update: 2 weeks ago I got a Webro WF100 cable from someone here and it fixed the issue. I'm looking to get another but the person I bought from is not responding so I'm just looking for somewhere to buy another WF100 cable. Male to Male about 2m for the upstairs TV.