what socket outlet

[russellsmiler]

Hi
as part of planning to fit twin wf100 to an outlet for freesat box,

I dont know what 2 gang socket plate is required.

it seems the options are
twin coaxial ?
satalite and coaxial ?
twin satellite ?

Anybody able to walk me through the differences?

Would be much appreciated.
Russell

 

[winston1]

No such thing as a satellite outlet. The sockets used for satellite cables are conventionally F types and that is what you would be advised to use for Freesat.

 

[Lucid]

The F type connector is the best option to choose for a wall socket.

Electrically it's a better "match" for joining two bits of coax, and that's regardless of whether it's satellite, TV signals, or FM/DAB. Once you have a bit of wire from the wall socket then you can put on the appropriate end to fit whatever connection there is on the device you want to plug in to.

 

[Doggit]

Twin satellite, or F connector wall plate from Toolstation.

What sky do, it to use shotgun cable from the satellite dish, take it though the wall and silicone it in, then put a pair of F plugs on the end. The wall plate is neat, but there will be a bit of signal degradation doing it this way. Taking a cable straight to the freesat box, gets the best signal possible.

 

[ericmark]

I think although having no break in cable is electrical best, having a pair of cables just coming out of the wall looks cheap and nasty. LAP do a grid system of switches, sockets, and brushes which can be used to make it look neater. These

brushes fit into these

see here and here allowing the inside at least to look neat. There are also standard TV and F type connectors which fit the same system, you can mix and match.

I use TV and F type simply to identify which system, satellite or freeview, it does seem the standard TV connector has two thicknesses of centre pin, using these

I have found some of these

have too thick a centre pin, not a clue where they came from in first place, but there are the easy way to adapt leads for F type or TV.

Be aware

these are NOT just connection boxes, inside the module there is a set of filters, these allow you to use one coax to take multi frequency signals and split them at the wall, they need another similar unit the other end to combine the signals. The same applies to some face plates, some simply give you a plug or socket, others have a braid break built in. TV or any other aerial device can receive a static charge, so when you plug in your aerial you can get a nasty belt, capacitors will allow TV signal through but not the DC static build up, so having the braid break in the socket from outside is good, however using these sockets to send TV signals around the house they will again stop DC so things like Sky digieye will not work.

With satellite signals they come from a LNB not an aerial so no need for braid break, in fact a braid break would stop them working as they need DC power up the coax, so F type connectors do not have any filters built in, but with TV wall plates there seems to be no standard which tells you which have built in braid break and which do not, I used the LAP grid with Sky so they don't have a filter to stop static.

Where a mast head amplifier is used, the amplifier has the braid break so no need for it in the socket, in fact again if fitted the amplifier will not get the DC up the coax it needs to work. As to best connector I am sure the N type is better than F type, however with high frequency signals some matching is required and N type is normally 50 ohm where TV is normally 75 ohm and old computer LAN cables were 95 ohm. I have seen coax as thick as my arm on some sites, this is not needed for TV. It's not the best you need but most appropriate for the function.

Location does matter, in my mothers house I would not expect to have problems with static build up on aerial wires, on my house I would, the braid break does not only stop static, it also is often a band pass filter which stops out of band signals from getting into the TV or set top box, I can transmit at 400 watt and I could be living next door to you, without the filter that strength of signal could upset your TV or set top box. However I have not been able to find a BS type number or EN BS number which identifies which wall plates have filters and which do not.

With telephone sockets we have two names "master" means it has spark gap, and capacitor fitted to stop static from outside (it also works bell on old phones) and "Slave" which means no components fitted, today the socket may also split phone and data, but point is it's easy to work out which is which. It seems some call sockets with filters "Shunted" and those without "Feed through" but it is not a generally used description. In the UK thunder storms are not that common and so we tend not to worry too much about static build up, other countries have a far bigger problem.

 

[ericmark]

No such thing as a satellite outlet. The sockets used for satellite cables are conventionally F types and that is what you would be advised to use for Freesat.

I agree from a signal point of view F type better, but from a safety point of view F type never have filters, braid break, or even a simple capacitor to stop you getting a belt when screwing in the connector, this is because with satellite you need a DC feed up the cable, same with mast head amplifiers. So there is a good reason to use TV push in plugs and sockets when connecting directly to the aerial, not F type, simply because many push in aerial sockets have the passive components built in to stop you getting a shock from static built up.

I would love to be able to advise use an XYZ box for Freeview, but I went to Screwfix and SatCure to try and find what a socket with static build up protection is called and what one without the protection is called. Sorry to say I could not find a universal name to identify which is which.

However referring to satellite connectors as F type and non satellite as TV does have some sense, no such thing as a digital aerial or a black and white (Monochrome) aerial, but the trade called wide band aerials digital and the TV licence of years ago refereed to the apparatus used to receive black and white signals (which would be the aerial) when clearly they were referring to the apparatus used to decode TV signals not the device which received them. However you would not get away with a black and white TV licence by painting the aerial black and white. (Wording today has changed)

So I would say TV plug and socket to aerial, and F type to everywhere else be it internal, mast head amplifier or LNB. As we hear a thunder storm we unplug the TV, however by that time likely there is already a static build up, reconnecting is even harder, I would have a wandering earth lead in my radio room, which I would touch onto the VHF or N type before I grabbed hold, and I have seen some heathy sparks come from them. And I did not work HF only VHF and UHF so quite small aerials.

The earthing of aerials is clearly wrong, as this would attract a lighting strike, however they do need a leak off path some 100MΩ resistors connected to earth or a spark gap and where possible capacitive links, since I transmitted on my aerials capacitive links were a non starter, but with receive only they are a simple safety feature I would want to see between any aerial and the user.

 

[winston1]

The earthing of aerials is clearly wrong, as this would attract a lighting strike,

In many countries it is mandatory to be "clearly wrong".

Actually an earthed aerial or a lightning conductor does not attract a lightning strike. It helps to discharge the atmosphere thus reducing the likelihood of a strike.

 

[bernardgreen]

Actually an earthed aerial or a lightning conductor does not attract a lightning strike. It helps to discharge the atmosphere thus reducing the likelihood of a strike

One opinion is that if the top of the earthed structure has sharp points then one polarity of atmospheric charge will be reduced by the electric wind flowing from the points. If the structure has spherical ends then no electric wind can be generated. https://en.wikipedia.org/wiki/Ion_wind

That said there is the opposing opinion that the electric wind assists the creation of the stringers (? name ) that form a path for the main discharge route and thus points will increase the risk of a strike.

This can help to keep lightining strike energy out of a building. Bring the aerial cable down below the point of entry and then U turn it back up to the hole with a U bend radius of about a foot. Fit a substantial earthed rod along side the descending side of the U and when the cable is struck by lightning the impedance of the U bend can cause the voltage spike to take the lower impedance capacitive route to ground by jumping off the cable and onto the earthed rod. Once the voltage spike has jumped and created a plasma route the majority of the currrent will take that path as well. It may not fully protect equipment in the building but it may well reduce the risk of fire and / or structural damage inside the building.

With modern TVs and other equipment that does not have an Earth in the mains supply the 0v of the electronics is floating somewhere around 115 volts AC ( mid point of the supply voltage ) by capacitive coupled voltage divider between Live and Neutral. Hence the screen of the aerial socket is at 115 volts but is current limited by the ( hopefully ) small values of capacitive coupling. This creates the "tingle" when touching aerial lead and the aerial socket and before the lead is plugged into the TV

 

[ericmark]

Thank you bernardgreen I attended a lecture about lighting and aerials, it was very interesting, it stated about lighting being attracted to sharp edges and elevated earthed structures so one should not mount aerials on gable ends as sharp edge or chimney as soot lined which would produce an earthed attraction, it also said how you should not earth an aerial as this would attract the lighting strike. However he also said how the wind often moves the ionised path so often having an earthed structure causes near misses.

As radio hams we had been earthing our aerials for years during electric storms, but it seems this is wrong, as you point out however it is good to have a path outside the house so the idea of the aerial lead being outside and dipping next to an earth rod seems very good. As radio hams capacitive decoupling was not an option, but it is with TV so simply selecting the correct TV plate with capacitive decoupling makes the aerial point far safer. Also having a connector where you can simply pull on the insulated cable to disconnect is safer than one which required you to unscrew it.

So first TV fixture needs to decouple, this may be the mast head amplifier or the wall plate, after that point then the F type takes over as best connector, however my set top box has like many others F type for connection to LNB and TV for connection to Freeview and it does make sense to keep F type for satellite and TV for terrestrial so they don't get mixed up.

 

[Sam Gangee]

See http://www.satcure.co.uk/tech/lightning.htm

 

[ericmark]

Clearly not UK as German sockets fitted, sad news that SatCure is no longer trading, that web site was good to get information. I suppose the web site will close soon. After my posts I spent some time looking for wording used this picture

shows the decoupling capacitors, and this picture

shows the problem when the socket is screened, without a screw driver and taking the socket apart you can't test it. So you have no idea what you are buying.

As to lighting strike if that happens it's an insurance job, loads of damage, and not that much you can do, lucky it's like winning the lottery, it rarely happens. However the near miss or simply just a high voltage gradient can give one some nasty belts, I for one do not like electric shocks, so want decoupling capacitors some where between the aerial and me. I don't care where, just want them some where, likely the mast head amplifier.

Until this question was asked I had not realised how hard it is to find out what you are buying.