How many coax cables can come off an aerial?

[SUNRAY]

When a mistake can result in wrong advice, then it needs a query, but when you know without question what is meant, then it is rather a pointless exercise, 220 volt, 230 volt, 240 volt and low voltage in most posts mean the same, but I tend to write low voltage (230) just in case, and I still call the unit inside a shaver socket an isolating transformer even though I know technically it does not transform anything.

Dyslexia rules KO.

THank you again.


PS wear dyd yoo lern to spel discleckcear?

 

[JohnW2]

Sorry I disagree. Have you no pride in your work?

I have pride in my ability to devise the simplest and/or most cost-effective etc. (and even 'more planet-friendly'!) way of satisfactorily achieving what I want, subject to it being (where relevant, which it isn't here) to issues of safety.

 

[securespark]

No he didn't lie. There may possibly be incorrect terms used in the original statement or the relaying of it here.

It was nearly 21 years ago, I can't remember exactly the words used, but that was the gist of it.

There are lots of posts on various forums of people getting poor Freeview reception, almost all of which are due to poor aerial installations.

In that (nearly) 21 years, I have never witnessed poor picture quality or freezing.

 

[securespark]

PS wear dyd yoo lern to spel discleckcear?

The joke I saw was "Syldexia rlues KO"...

 

[SUNRAY]

I would hope the B&Q splitter has 3 resistors, not 2. But anyway such splitters are lossy, just over 6dB rather than just over 3dB for a properly designed one.

Hah? Please check your facts before posting potentially incorrect information

But at the end of the day TV aerial installations should be done properly, not bodged. There are lots of posts on various forums of people getting poor Freeview reception, almost all of which are due to poor aerial installations.

And most of those installations are done by supposed experts, Hmm.

So if it's to be done properly... let's start with the aerial.
The vast majority consist of a lump of aluminium, stamped out vaguely in the shape of a folded dipole. then we crimp a random bit of metal on each end, maybe copper or brass - Oh a nice bit of dissimilar metals there, which in no time at all start reacting and forming diodes and all of a sudden our 300Ω folded dipole is anyrthing but 300Ω oh but of course in a bid to make the balanced 300Ω look something like 75Ω we place it very close to a director. On the other hand the screw terminals are more likely to be mild steel these days and again in no time at all they rust, only now the reaction is destructive and sooner or later one of the steel bits developes an airgap with the aluminium, if it's the earty side do you know what effect it has? well I'll tell you, it has sod all effect, the aerial keeps working and picking up a signal on what is now a random single ended something or other.

C'mon Winston look at the whole picture and the real world, we start with a rubbish bit of bent metal on the chimney with a balanced element and terminate our unbalanced coax across the 2 ends. The other end of the coax is terminated into a Belling Lee coax plug, well let's agree it's not actually terminated as the copper (or copper plated) centre conductor is simply slipped inside the aluminium pin on the assumption it will make contact, oh and while we're at it we're adding another non linear diode into the circuit. Of course we no insist on using a quality cable like RG6 which of course is an aliminium foil in contact with a copper braid and introducing yet more diodes into the mix. Then we plug this mishmash into our nice shiney all singing all dancing computer based device, the first part of which (as far as the aerial is concerned) is a capacitor. I suppose at some frequency it might be 75Ω and if we're really lucky that might happen within the band of frequencies the device is designed to work in.

Basically we're talking about cheap domestic consumer rubbish which in no way conforms to anything like a proper 75Ω designed system. Making sure all the additional devices some people insit on adding in the middle are all perfectly designed and install somehow seems a bit pointless.

All the ones I have seen transform one output to 110/120v.

Is that the response from an intelligent person?

I think not, that dribble is totally meaningless and factually wrong.

 

[Lucid]

I have an extension in progress & would like to put in a coax socket for terrestrial, I already have an arial and cable at the other end of the house (aimed at a local booster station). Do I need another arial?

Thank you

Dain

Hi Dain,

Where an aerial system has been properly installed so that it delivers the recommended signal level to a TV, then it should easily withstand splitting two was so that the signal now feeds two TVs. There are some caveats though to do with signal levels and how far you want to send the signal after it is split.

Splitting the signal two ways will reduce the level by a little more than half for each set. That sounds dramatic, but with decent signal to start with, it would be possible to split the signal 4 ways (that's halved, and then halved again) and still provide enough for the TV to happily work with.

A simple, good quality, shielded 2-way passive splitter such as this or this will do the trick for you.

Given that these cost under a fiver a piece, and you're only splitting two ways, then it's cheaper and quicker to try them than faff around testing signal level tolerance to loss with in-line attenuators of various dB values.

 

[winston1]

Hah? Please check your facts before posting potentially incorrect information

If you DON'T know something DON'T accuse another of posting factually incorrect information. Cheap splitters have THREE resistors either 24Ω in delta or 75Ω in star. The loss to each output is theoretically 6dB, though in practice slightly more, FACT. Properly designed splitters with an RF transformer have a loss to each output of 3.7dB, FACT. It is even written on them.

 

[winston1]

And most of those installations are done by supposed experts, Hmm.

So if it's to be done properly... let's start with the aerial.
The vast majority consist of a lump of aluminium, stamped out vaguely in the shape of a folded dipole. then we crimp a random bit of metal on each end, maybe copper or brass - Oh a nice bit of dissimilar metals there, which in no time at all start reacting and forming diodes and all of a sudden our 300Ω folded dipole is anyrthing but 300Ω oh but of course in a bid to make the balanced 300Ω look something like 75Ω we place it very close to a director. On the other hand the screw terminals are more likely to be mild steel these days and again in no time at all they rust, only now the reaction is destructive and sooner or later one of the steel bits developes an airgap with the aluminium, if it's the earty side do you know what effect it has? well I'll tell you, it has sod all effect, the aerial keeps working and picking up a signal on what is now a random single ended something or other.

C'mon Winston look at the whole picture and the real world, we start with a rubbish bit of bent metal on the chimney with a balanced element and terminate our unbalanced coax across the 2 ends. The other end of the coax is terminated into a Belling Lee coax plug, well let's agree it's not actually terminated as the copper (or copper plated) centre conductor is simply slipped inside the aluminium pin on the assumption it will make contact, oh and while we're at it we're adding another non linear diode into the circuit. Of course we no insist on using a quality cable like RG6 which of course is an aliminium foil in contact with a copper braid and introducing yet more diodes into the mix. Then we plug this mishmash into our nice shiney all singing all dancing computer based device, the first part of which (as far as the aerial is concerned) is a capacitor. I suppose at some frequency it might be 75Ω and if we're really lucky that might happen within the band of frequencies the device is designed to work in.

Basically we're talking about cheap domestic consumer rubbish which in no way conforms to anything like a proper 75Ω designed system. Making sure all the additional devices some people insit on adding in the middle are all perfectly designed and install somehow seems a bit pointless.

You are talking about a cowboy* installation done by a person in the small ads moon lighting and paying no tax. Professional installations use decent aerials well made with baluns. They solder the coax plugs and use decent WF100 cable.

Dissimilar metals are not restricted to aerials. Just look at 13 amp sockets with brass earth terminals riveted on to galvanised mild steel plates for example.

* Calling these people cowboys is an insult to those that round up cattle on horseback, but sadly the term seems in common use.

 

[winston1]

Is that the response from an intelligent person?

I think not, that dribble is totally meaningless and factually wrong.

Indeed I am an intelligent person. UK shaver sockets usually contain a transformer with 2 outputs labelled 240v (or thereabouts) and 110v (or thereabouts). FACT. Have you not ever seen one?

 

[SUNRAY]

If you DON'T know something DON'T accuse another of posting factually incorrect information. Cheap splitters have THREE resistors either 24Ω in delta or 75Ω in star. The loss to each output is theoretically 6dB, though in practice slightly more, FACT. Properly designed splitters with an RF transformer have a loss to each output of 3.7dB, FACT. It is even written on them.

Yes you are absolutely correct and I'm tempted to let you go on making the same ignorant mistake for the rest of you life.

 

[SUNRAY]

Indeed I am an intelligent person. UK shaver sockets usually contain a transformer with 2 outputs labelled 240v (or thereabouts) and 110v (or thereabouts). FACT. Have you not ever seen one?

Now you have clarified your post it does make sense.

 

[SUNRAY]

You are talking about a cowboy* installation done by a person in the small ads moon lighting and paying no tax. Professional installations use decent aerials well made with baluns. They solder the coax plugs and use decent WF100 cable.

Dissimilar metals are not restricted to aerials. Just look at 13 amp sockets with brass earth terminals riveted on to galvanised mild steel plates for example.

* Calling these people cowboys is an insult to those that round up cattle on horseback, but sadly the term seems in common use.

Th OP is all about a domestic installation with one or two TV's in a house. That is where I'm aiming my replies.
Even the big professional guys use 'install quality' aerials in domestic situations.

WF100 is an OK quality of cable. But I'd generally get involved with better quality products.

13A sockets are not usually mounted high up on roof tops in poor quality enclosures.

 

[endecotp]

Coukd the confusion between -3 dB and -6 dB be the difference between dB mV and dB mW ?

SUNRAY, I think you need to discover the “ignore” button. I use it a lot and it makes the forum much more enjoyable.

 

[winston1]

Yes you are absolutely correct and I'm tempted to let you go on making the same ignorant mistake for the rest of you life.

What same ignorant mistake?

 

[SUNRAY]

My sincere apologies to endicotp.

I confused you post for one of Winstons