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Cable, Connectors and Leads  

Subjects on this page are listed in the following order :  

The Importance Of The Cable And The Routing Of It  (including Surface Plates )

The Three Main Types Of  CoAx Cable ( = FM / DAB / TV / Satellite Cable)

"Low Loss" CoAx

Alloy Foil Type "Satellite" Cable

Copper Foil Type "Satellite" Cable

Twin Satellite Cable ("Shotgun" cable)

Joining Two Cables Together

Routing Mains Cable Next To Co Ax ? (and electrical interference generally)

SCART Leads And Phono Leads

SCART Switch Boxes

TV Leads / Fly Leads

Co-Ax Plugs And F Connectors

It may be budget Coxial and cable does degrade over time anyway. If you must join a new length

of cable outside, we recommend using the method shown below. The use of CoAx plugs

covered in insulation tape is very bad practice.....

After the cable exits the aerial`s junction box introduce a slight downward gradient to it help

prevent the ingress of water.

Now (on a cradle mounted aerial) comes the big question ! Do I route the cable forward (and then

down the pole) ? Or do I route it back round the reflector and then onto the pole (which is what

aerial manufacturers recommend these days) ? Well we did a series of tests and found no

measurable difference, I`m not saying there isn`t any difference, I`m just saying we couldn`t

measure it. It certainly looks worse if you route it back round the reflector though !

Next use decent quality insulation tape to secure the tape to the outside of the pole, preferably on

the North side so as to minimise exposure to the sun. The use of cable ties is not recommended

as they degrade in the sunlight and when they fail you don`t want to have to go back up to replace

them ! Running the cable down the inside of the mast can also be problematic due to the

possibility of chaffing on the cut end of the pole, plus any wind movement can cause the

downlead to bang against the inside of the tube in a most annoying fashion.

Let`s be honest, you`re better off avoiding surface plates, but if you have no choice but to use one, make sure it`s a screened one (as in those above). This is particularly the case in a poor signal area, a site prone to interference or if it`s a satellite signal. Only an absolute bodger would fit (or even sell) an unscreened satellite outlet plate.....  

The cable should not be kinked, route it like the one above right and not like the other one.

The Importance Of The Cable And The Routing Of It

A fair proportion of our call outs for "poor picture" are not caused by the aerial at all, but by the

cable. Usually it is perished or cracked or just bodged in the first place, e.g. a kinked cable or

joined together with insulation tape etc etc. If it is a fringe area and there is a long cable run it

could even be due to the use of "budget Lo-Loss Co-Ax" cable. The cable is just as important as

the antenna (and any amp or splitter, if fitted) in providing a decent signal on your set. The cable

should be changed as a matter of course if any work is undertaken on the aerial, unless you are

sure it is sound and of good quality. Whilst on the subject of cable / connectors, we recommend

avoiding the use of Surface Plates if at all possible, and this is especially the case if a PSU

(for a mast head amp) is used in the system. Apart from providing an extra join in the downlead,

the cable is often "kinked" (at the point where it is attached to the PCB at the rear of the plate) and

this is bad practice from the RF point of view. Cheap unscreened faceplates can be particularly

problematic, don`t use them. We advise utilising the cable direct from the aerial straight into your

TV or Freeview box. If you have one of the latter the cable should always go into that first.

We are more than willing to give advice to those actually purchasing from us.  

Could those only seeking information please just find the answer somewhere on this site,

or ring an aerial installer local to them, or call the reception advice phone numbers.

Ever wondered why some aerial installations use

loads of tape on the mast, and in pretty imaginative patterns ?

No I didn`t think you had, but I`ll tell you anyway.......

It`s so installers can recognise their own handiwork !

I hesitate to use the term “tag” because that`s the name used by those scroats who deface so many things with their ugly and depressing graffiti.

Note the X Beam aerial falling apart.....

Bypassing a cheap (unscreened) surface plate gave an increase in signal of nearly 2 dB on

average ! To put that into context that`s almost as much as the increase in signal you would get

by swapping from a Log 40 (a medium gain aerial) to a DY14WB (a high gain aerial).

Furthermore the elimination of the surface plate also gave a huge improvement to C4 Teletext

which had always been problematic at this location. The gain in signal level cannot have been

due to a decrease in the number of “connections” because the plate (one connection) had

actually been replaced by two, i.e. Plug > Back to Back coupler > Plug. The fact that the surface

plate was an isolated type was very significant because when the isolating capacitors (which

were 3nF at 3kV) were shorted out most (but not all) of the attenuation disappeared.

Screened surface plates are deeper than unscreened types

so make sure you fit a pattress box of sufficient depth. If retro

fitting to an existing shallow pattress box then we sell spacer

plates to gain an extra 7mm depth. They can also be useful if

you want to increase the clearance behind a surface plate so

as to ease a kinked cable.

Also see surface plates incl diplexed.

Placing a "hole tidy" (sometimes called a cable tidy or

grommet) around the cable just where it enters the house

provides a neat job and it`s quicker / cheaper than a wall

socket, and their matt finish means they`re ‘paintable’

Remember that a “retro fitted” surface plate / wall plate isn`t

going to be neatly flush fitting (not unless you chisel out the

wall.......) and a decent screened plate will require a pattress

box sticking out about an inch.

We have had customers complaining of poor signal or

intermittent interference who have gained significant

improvements by simply dispensing with the surface plate. Unscrew it from the wall and check if

you have a bit of slack in the Co-Ax leading to the rear of the plate, don`t pull it too hard though !

If you have enough spare cable, detach it and then unscrew the PCB from the back of the surface

plate. Now throw it in the bin. Gently pull some of the downlead out and push it through the hole

which you have just exposed in the plate. Replace the plate on the wall and attach a Co-Ax plug

to the stub of cable, then join an extension to this.

Alternatively replace the plate with a decent screened non isolated type, like this one.

If you plan to recable your aerial yourself, a typical cable run from the chimney is about 15 m. One should always buy a little more than is required as few things are more frustrating than

completing the job only to discover you`re short of cable !

It is always a good idea to install a service loop of cable (about 4

to 5" in diameter) in an inconspicuous location at the bottom of the pole, this can save much time and hassle if you need to subsequently fit an amplifier or splitter.

If your downlead is cut through, best practice is to replace the lot.

The piece of cable in the above picture was run over a roof without utilising clips to secure it and the action of the wind

has worn it away on the slates. Water can then seep into the hole and this can have a deleterious effect on the signal.

Worse still is what can happen when the water reaches whatever the cable is plugged into.........  Incidentally foam

filled cable tends to impede the water using your cable as

a fall pipe rather better than air spaced cable !

The picture on the left is of a “slate clip”  in use. Care should be taken not to crush the cable beneath the wire(s).

The Three Main Types Of CoAx Cable

All TV downlead should be 75 ohm in order to maintain an "impedance matched system"

but there are 3 main types of coaxial cable and they are listed below.

Whilst routing downleads do not introduce sharp bends or kinks to them, the minimum recommended curve being about 10x the cable`s diameter, so 7mm cable would equate to

around 7cm, or more if possible. Always use the correct size clips for the cable. This is for two

reasons. Firstly it`s important to avoid crushing the cable, secondly the correct size clip will hold

itself on to the cable (rather than you holding it with your fingers) whilst you hammer it in, thus

avoiding the possibility of said hammer greeting your finger tips.

Horizontal runs across brickwork should use a clip every other brick, vertical runs should use a

clip every 10 courses. Try to fix the top and bottom clips of the run first, then add the intermediate

clips, this helps to ensure a straight run rather than looking like a dog`s hind leg....

Always use perpendicular runs, vertical or horizontal, diagonal runs look absolutely crap.

Cable can be painted if required, which is useful if the house changes colour during the cable

run, or you have a white house but the cable also runs over the roof. In the latter case a white

cable over a roof (usually dark grey ! ) looks terrible, so go for black cable and paint it where it

runs over the white walls.

If you`re splitting the signal always use a splitter (or an amplifier, if required), never just bodge

it together with insulation tape. It is often neater and more convenient to split the cable outside

and this can be achieved by utilising a weatherproof splitter box (or an external amplifier). If using an amp, particularly a high gain type, try to avoid running the input and output cables side by side, as this can sometimes introduce "crosstalk" to the signal, especially if using cheap crappy cable.

It may be easier to drill a hole through the window frame but it is bad practice to route the lead

this way. It will encourage rot and if you replace your window(s) the cable will then need to go

through the wall anyway. Incidentally if you ever have replacement windows fitted, do not allow the

installers to "wedge" the cable under the frame. Apart from the fact it looks awful and the crushing

of the cable should be avoided, when you eventually have the downlead replaced (cable does

degrade over time) the old cut off stub will be left in situ for evermore !

Graph of cable loss

(in dB per 10m) for the three main cable types.

Note how at the FM

frequencies the losses are far lower than at TV and satellite IF frequencies. The latter are the lower down converted frequencies from the LNB. Also note the poor performance of the thin type double satellite cable.

Also see interference tests for the various cable types.

This is the lower quality grade of satellite cable, but even the cheapest is far better than "budget

low loss" CoAx. The major difference between satellite cable and "low loss" Co-Ax is the addition

of a layer of foil screening just under the braiding, i.e. (for simplification) it`s "double screened".

The latter can have a big effect in helping to minimise interference and decrease loss. With RG6

type cable that foil is usually aluminium or some similar material, although the cheaper brands

seem to use a plastic film covered in a metallic substance. To be quite honest it`s perfectly

suitable for virtually all TV/Radio (i.e. UHF/VHF) applications and this is particularly true if it is a

branded product, e.g. Webro. Although Sky don`t recommend this grade of cable this is more to do with the fact that copper/copper type cable lasts longer than alloy foil type and I would say that it`s fine for most satellite use provided the down lead is not of excessive length.

Note, RG6 is technically the size of the cable (i.e. 6mm in diameter), and as such most Co-Ax

cables are also RG6, but to most in the trade RG6 has come to mean alloy foil satellite cable,

because it`s a lot easier than saying “alloy foil type satellite coaxial cable”  !

Typical loss (per 10m at 800MHz) of RG6 type cable is about 1.9 dB, i.e. a typical 15m

run would lose just under 3 dB               (a 6dB loss is half )

"Low Loss" CoAx   

(We do not sell this type of cable)

Traditionally everyone used "Low Loss CoAx" for virtually all TV (and FM radio) aerial cable and

years ago much of  the CoAx on the market was of pretty reasonable quality with high percentage

screening cover. The vast majority of low loss Coaxial cable sold these days is absolute rubbish.

This is an objective fact and can be proved by just looking at the exposed screening in the picture

above. There`s probably only 40% screening coverage on 42 strand "budget low loss CoAx".

How much additional interference could that let through ? Don`t get me wrong, if you live in a

reasonable signal area and/or the downlead isn`t too long, it should still work reasonably. But

with particular reference to the "Digital cliff edge" it`s just not worth skimping on the cable to save

a few of pounds ? How much did your TV cost ?

The vast majority of brown (or sometimes white) downlead is of the budget Co-Ax variety, though

(just to make things even more complicated....) in 2007 we finally began stocking copper/copper

satellite cable in brown as well as black & white !

A more positive check can be made by taking off the plug and closely examining for the presence

of an additional screening sheath. If it has all been trimmed off, the latter may not be visible under

the outer insulation so removing a small section of this may be necessary.

If the cable is old thin stuff, (i.e. less than 6mm) it should be changed if at all possible.

Most new build houses use ultra cheap CoAx to wire up the pre-installed TV points. If you have

any input into the build of your house, I would insist on the use of decent cable. Quite apart from the superior performance of satellite cable at TV/UHF frequencies, you never know whether you (or someone who buys your house) may need to utilise existing wiring to transmit signals at satellite frequency, see Diplexers.

I`m sure electricians know more than us about "ring mains", but, with respect, we know more

than they do about RF. So take our advice and don`t let them fob you off.

Typical loss (per 10m at 800MHz) of "low loss" CoAx is approx 2.7 dB,  i.e. a typical 15m run

would lose just over 4 dB                (a 6dB loss is half )

Alloy Foil Type Satellite Cable  

(We do not sell this type of cable)

Copper Foil Type Satellite Cable  

(We only sell this type of cable)

The third type of cable also has "double screening", but this time the foil is copper. This grade of

cable is the best of the generally available types, though when I say generally available it`s not usually sold at DIY shops.

To be frank, it`s overkill for DAB/FM (i.e. VHF) but being a perfectionist I like that. There isn`t a big difference in performance on UHF (i.e. TV) or even satellite, but copper/copper cables are reputed to last significantly longer than alloy foil types, which is why Sky only recommend this grade.

But the price difference on a typical 15m run is only a few pounds, so why not fit the best ?

This cable is suitable for FM, DAB, TV and Satellite, and it is CAI / Sky approved.

Our cable is the foam filled type as opposed to air spaced. Although signal quality wise there`s

no difference between them, foam filled tends to resist kinking slightly better. Furthermore if

you`re unlucky enough to get water into the cable then foam filled tends to resist water running

down the inside of it better than air spaced, though it can still permeate down through the outer

braiding under certain conditions.

This is the only grade of cable we sell in Black, White or Brown by the metre at 50p, or by the reel

at 50m for £20 or 100m for £40   

Note if you require white or brown cable please specifically request it,

because if not we would normally send black !     

Typical loss (per 10m at 800MHz) for this type of cable is 1.8 dB, i.e. a typical 15m run would lose just over 2.5 dB             (a 6dB loss is half )

Note, we now stock a superior type of F Conn at 75p (or 50p ea for 5+).

Routing Co Ax Next to Mains Cables ? (and general electrical interference)

We`ve frequently been asked whether it`s OK to run Co Ax next to mains cables and, to be frank, we didn`t really know for sure. We finally got round to trying to find out in Aug 2008 with a simple but, we feel, appropriate experiment.

We taped a 12m length of Low Loss CoAx,

and of copper/copper satellite cable, to a

mains flex. Then we used a signal generator

to supply the signal, and at the fairly low level  

of only 65 dBμV as well, to try and encourage

as much chance interference as possible.

But how to detect the noise ?

We used a spectrum at first, but really that was just trying to be flash because a TV is just as likely to reveal any interference !  

As an electrical load we thought a vacuum

cleaner would suffice, and as ours is 1800W it should certainly draw some current, and hopefully generate a few mains spikes on

start up.

We connected up the Sat cable, then rather

tentatively we switched on the vac, there was

no interference whatsoever. We then switched the vac on and off repeatedly to try and

generate some spikes on the mains,

still no interference. Next we used a 6dB

attenuator to drop the signal even further, still no interference. Finally we routed the cable bundle through 20ft of alloy tubing to simulate ducting and keep any radiated interference close to the Co Ax (?), result still no

interference.

We also repeated each experiment with ordinary Low Loss CoAx, and I have to tell you that in this

test there was no detectable interference with that either. That said, I have heard of cheap Low

Loss CoAx introducing RF crosstalk to adjacent cables when bundled together, although this

obviously isn`t at 50Hz main frequency. But see below......

That all seemed cut and dried, and in fact I even put the first draft of the results on the website,

but something in the back of my mind was nagging away at me.....

I decided to repeat the experiment with a load which may generate more electrical noise.

I dragged out my trusty 1980s Black & Decker drill and thought I`d use that as a load instead.

Incidentally those were the days when B & D made decent tools because that drill has had some

use, and I mean some right hammer, and it still works fine, other than a replacement chuck.

I checked that when used right next to the set it did actually introduce noise to the screen, and it

did if one “played” the switch and the variable speed (under load).

The vac on the other hand didn`t produce any noise thus indicating that the above tests with it

were only valid for electrical loads which are suppressed, which most are to be fair.

Using the copper/copper satellite cable, with the mains cable from the drill was taped to the side

of it, there was no interference on the set or blocking on the Freeview box we used as a test.

But, and this is significant, as stated above there was a bit of noise if the drill was operated right

next to the TV or the digital STB. The drill was producing noise, which can interfere with the

tuner(s) by direct radiation, i.e nothing to do with the signal cable.

But when the drill was operated at a distance of more than a few metres away (when using the

satellite cable) there was no interference introduced to the signal via the cable.

We then repeated the test using Low Loss CoAx and I`m pleased to say that my negative opinion

of it was vindicated. With the signal cable taped to the mains cable from the drill there was

significant interference on the screen and blocking on the Freeview box.

Just to be sure we swapped back and forth between them and the results were consistent.

I thought “Low Loss” was crap, but I didn`t think it was that crap.....

We were in the swing of it now, so we next tried RG6 type satellite cable and it was far better than

Low Loss. In fact there was hardly any difference between it and the copper foil type cable.

Picture of cable bundle exiting the tubing and supplying the signal to the TV, just behind it.

Whilst I`m not prepared to say anything for certain, especially with RF, I think it is reasonable to

conclude that mains borne interference is not usually introduced to the signal through the signal

cable provided it is satellite grade.

The same cannot be said for Low Loss type CoAx cable.  

However even with the best quality cable it is still possible to get interference but that is more

likely to be by direct radiation onto the tuner(s). It could also be through unscreened splitters,

amps or surface plates or even straight onto the aerial, though Baluns are supposed to limit the

effects of it and Log Periodics even more so. Also try tilting the aerial up at the front a bit.

It is also possible to get noise up through the mains and the use of filter type mains adapters

may help with that, may being the operative word because all TVs/STBs should normally have internal mains chokes anyway.....

The best remedy for interference is to track down the cause and cure it at source, e.g. if your

central heating thermostat is noisy and creating electrical interference replace it with a

suppressed one. Other significant causes of interference for digital TV can be “hands free”

phones, particularly digital ones. Try moving the base station away from the TV or STB.

Having said all of the above, I`d still only route CoAx cable next to mains cable if I really

had to. But if you have no choice I`d definitely make sure it was satellite grade.......

Also see this interesting customer report on cable interference problems.

Freeview picture whilst under test

with satellite cable

Freeview picture whilst under test

with “Low Loss” cable

SCART Leads & Phono Leads

SCART leads were introduced by Philips (as "Peritel") in 1977 and are used to connect your TV/Video/Digital box etc etc. They bypass the tuner(s)/modulator(s) on the units(s) and supply the signal in its component parts of Video + Audio (left) + Audio (right).

SCART Switch Boxes

More and more devices require connection to TVs and it is becoming common to run out of

available SCART sockets on the set. This is where SCART Splitters or Switch Boxes come in.

We do not recommend the former because all the SCART sockets in the system are permanently

connected together. This can lead to spurious patterning or interference on the picture and

sound, particularly if more than one device (e.g. your Video and your DVD or Sky) are switched on

at the same time. The Switch Box has it`s down side in that one must manually switch over from

one device to the other. Terrible, you have to get up out of your armchair ! Unfortunately it is the

only way of avoiding the aforementioned signal problems. If you have two SCARTs on your set

you can always utilise one of the TV switchable sockets for the most used device and the other

for the switch box. Thus you don`t need to use the manual switch as often as you would think.

ATV sell 3 way manually switchable SCART boxes.    

TV Leads / Fly Leads

If you have a wall socket (which we don`t recommend, particularly budget unscreened types) then

you need a lead from there to the set. Also the same is required to connect up your Video to the

TV. Fly leads are relatively cheap so make sure you buy a decent one. In fact Digital UK advise (in

their Aerial Installer Newsletters) that "blocking/sound disturbance is often due to an old or

damaged CoAx fly lead running between the TV/STB and the wall plate". When they say "often"

they only mean in about 5% of cases, but then again it`s a cheap thing to eliminate, so try it !

The easiest way to spot a crap fly lead is to check how thick the cable is, it should be at least

6mm in diameter. Of course it should also have double screened cable (though this is somewhat harder to ascertain) and it is also important the plug is crimped to the end (see below), rather

than just moulded on with the centre core soldered, because there are few things more annoying than an intermittent connection in your fly lead and in our experience this is most often caused by the centre core breaking off (at the soldered joint) where it`s been put under stress.

Our Fly Leads are white, use 6mm quality double shielded cable and, just as significantly, utilise

crimped on plugs. To be honest these leads are probably the biggest bargain we sell and I can`t understand  why we don`t sell even more of them !

To quote that well known idiom “all that glitters is not a decent fly lead” (or something like that)

and this picture illustrates this perfectly. The top lead looks very flashy, gold plated in fact

(gimmick, unless you live in a salt mine....) and it`s “Standard Linear Bandwidth” no less -

whatever the hell that means - but it`s got a soldered on plug ! A customer bought the lead in to

show us and kindly donated it to the aerialsandtv.com website. We cut it open to show the joint

and took a picture, so here it is. Note that Gold plated plugs should only really be used with Gold

plated sockets, because any advantage appertaining to said Gold plated connectors will be vastly

reduced otherwise, so basically, I wouldn`t bother with them.......  

Remember looks aren`t everything, substance wins over style in my book, every time.

The “fly” lead below is the one we stock (in 2m and 4m lengths) and they really are good.

The 6mm  “double screened” cable is well worth having but what`s just as significant is the

crimped on plug, no weak soldered joint here.... What was interesting is that even the suppliers

couldn`t tell us if the plugs were crimped on, the only way we could tell was to cut it open !

Also note the RF chokes, normally hidden under the blue plastic covering  

CoAx Plugs And F Connectors

The CoAx plug fits on the end of the aerial downlead and pushes in to the Co-Ax

socket on the TV, or Set Top Box, or Amplifier / Splitter, see fitting a CoAx plug.

An F connector is usually only fitted on a satellite lead (from the dish) or a mast head amp down lead, or a splitter, and screws onto the STBs socket, see fitting an F connector.

Other signals and voltages can also be sent or received via a SCART.

These “other signals and commands” can also give rise to odd picture blanking effects on some

combinations of TV and source. For instance I found my Freeview plus recorder was giving weird

blanking and synch faults when the TV was switched to TV and the Freeview plus box was

switched on. I found that by switching the “SCART setting” from RGB (Red Green Blue) to CVBS

(Combined Video Blanking Signal) the problem cleared. I`m sure if I`d experimented with

disconnecting various pins on my SCART cable I`d have sorted it out anyway, but I didn`t have

time for that ! Pin 16 (Fast Blanking Input) can be guilty of giving picture problems, but basically if

you only leave Video and Sound “in” (to the TV) pins connected it`s likely you`ll cure any unwanted

effects. Experimenting with pin disconnections may take some time but it is always an option if

you`re getting desperate, and it`d cheaper than getting a TV engineer out !

There`s a full list of the pin functions on the above link.

The big advantage of using SCARTs (rather than modulated signals at RF through the tuner) is

that the risk of RF co-channel interference is eliminated. In addition stereo signals can be sent

between units. One major disadvantage of the SCART system is the physically weak construction

of the sockets in the actual TV and indeed the plugs themselves. For this reason I would avoid

pulling the SCART plugs in and out any more than is absolutely necessary, use a SCART

switch box if necessary. In fact if you lose sound or video from a device (which is connected by a

SCART) the first thing I would do is check if the lead is firmly pushed home, then I would try a

different lead.

I may be obsessed with quality but I wouldn`t advise buying one of those ridiculously expensive

"professional" type SCART leads. The retailers make more money on the SCART lead than the

actual TV or Video they sell you. Take it from me they give no improvement over any "individually

screened" SCART on which there is a screening foil over each individual wire plus over the

whole bundle (see picture), also known as “U Type cable”. The latter are worth buying and they

can sometimes eliminate annoying picture interference type faults usually caused by the TVs

Video out signal (if provided) cross talking with the video in signal from, for instance, your

Freeview box. Individually screened SCARTs  don`t cost that much more than budget “overall

screened" types and any extra cost is worthwhile over a budget SCART which  only has a

screening foil around the whole bundle of wires. The latter can usually be identified by their

smaller diameter cable. Our suppliers inform us that U type cable is OK for lengths up to 15m,

though just to be on the safe side we only stock leads up to 10m !

ATV sell individually screened SCART leads  in lengths of 1m, 3m, 5m and 10m

Personally I think that Phono leads are superior to SCARTs as the plugs (and the sockets in the

TV) are far more robust. Phono leads tend to be used on non European market TVs but are also

used on Hi Fis and some other audio visual products in this country.

In addition a switching voltage is sent over the SCART lead which

automatically switches the TV to the AV (or EXT) channel.

I must confess I do not like this function as it can be confusing when

setting up the system and also when in use. Furthermore if you have

two devices connected to your TV by SCARTs things can get even more

interesting. Many spurious effects can be eliminated by removing this

switching system and the easiest way to do that is by disconnecting pin 8

of the SCART, which is the one which provides switching voltage. You`ll

now have to manually select the input.

Take back control over your TV, remove the SCART pin 8 !

The number of the pin is usually found on the SCART plug.

Holes drilled through the wall should be from inside to outside and with a slight downward inclination to prevent any possibility of water ingress. If any mains sockets are present any hole drilled in a spot diagonally away from them should reduce the chances of hitting the cabling.

When a cable is routed across a roof it should be clipped to the roof slates at regular intervals

to prevent it moving in the wind and being worn away by the slates. The resulting holes let in rain water which seeps down the cable and ruins your TV tuner, or whatever else it`s plugged into.

If you have had an aerial installed, always check to see if the installer has clipped the cable to the roof slates and unless he`s got a cast iron excuse *, I would insist that he does so.

Any cable over a roof should run perpendicularly straight down it. Apart from the fact that a diagonal run looks terrible this will also stop any snow build up (remember that ?) from putting strain on the downlead. If the cable was run diagonally by your aerial installer, you chose the wrong one to do the job *.

* severe access problems would be mitigating circumstances.

If you accidentally damage the

brickwork, whilst drilling the hole,

we sell “blow out covers” in brown

or white. Incidentally these are just

to cover up any “blown out” brick

work, they are not primarily intended to prevent water ingress, you should silicone the hole and use a “drip loop” just under where the cable enters the wall to do that.

A Slate Clip is simply

a few strands of

galvanised lashing

wire (as found in our

lashing kits) cut to

around a foot long,

then bent into the

shape in the picture

and wedged under

the slates to secure

the cable. The number

of strands used would

depend on how the

tight the slates are

against each other.

Joining Two Cables Together

Obviously it is preferable to have a continuous cable run with no joins in it. Unfortunately this is

not always possible and if the following method is used, a join which would be reasonably

acceptable can be made. Screw an F connector onto each end and then utilise a “Back to Back”

to join these two ends together, see picture. If the joint is outside then self amalgamating tape

must be used to waterproof the joint, not ordinary insulation tape ! Cut off about one foot

(we sell it by the 10m reel and also by the foot) and remove the backing layer. Start wrapping the

tape round the joint about 1 to 2 inches above the join (stretching it to about half it`s width whilst

you do so) and finish the same distance the other side. If possible try to install the joint so that the

cable runs downwards either side of it (so water will run away from the joint) and better still place

where it is sheltered, e.g. under the eaves. No cable should be installed where it is under strain

but obviously this is even more important where it is joined.

Provided the above is executed correctly this gives a reliable and waterproof joint.

(We sell 2 x F-conns, an F-conn B to B and one foot of self amalgamating tape for £3.25)

Double Satellite Cable

(also known as "Shotgun cable" or 'Twinsat')

This is a variant of satellite cable whose use has mushroomed

since the advent of Skyplus (which requires two separate feeds

from the LNB to feed its two tuners) but the cable can also be used

for any install requiring two separate feeds from anywhere to

anywhere, e.g. from two separate (i.e. not diplexed) aerials. If you need to run two cables it`s undoubtedly a lot neater. The 2 cables can easily be pulled apart to run the final distance(s) as individual runs and they are often routed to two way surface plates,

i.e. 2 cables in > to 2 sockets. You do need special (wider) clips to tack it to the wall though !

There are two main types of Twin cable, the first is comprised of

two standard cables (approx 6.5mm ea) and its performance is exactly the same as the individual cable would be.  

We only sell this variant, in black, copper/copper and foam filled.

However there is also a second type composed of two thinner

cables (approx 4.5mm ea) and its performance is really pretty bad,

see the graph above.  We do NOT sell this cable. The thinner cable has two advantages. First it`s significantly cheaper. Second it fits through the standard size drill holes that most installers use. This is why Sky has sanctioned its use despite its performance being so inferior that a well known manufacturer hinted to me (off the record) that they were ashamed to produce it. Even Sky only recommend its use on runs up to 20m, though many in the trade would only use it up to 10m, and the most quality conscious aerial installers would only use it up to, well, 0m.

Of course, this isn`t to say it won`t work fine if it`s a short run, or you`re just lucky, just as with

"Low Loss" CoAx. Many bodges in this trade, and indeed in life, work for many people, but that

doesn`t make them right. These people have obviously never heard about 4" Fence Posts,

and they wouldn`t pay the extra for them even if they had.

The thinner cable does have another disadvantage, standard Co-Ax and F Connectors don`t fit it !

Push in CoAx connectors can be used for TV (UHF) or FM/DAB radio (VHF), though DAB actually uses F connectors in most cases. F connectors can also be used in place of CoAx plugs (assuming there is a corresponding F socket obviously ! ) but it is very bad practice to use CoAx plugs/sockets for satellite work.

CoAx plugs are more convenient (as they are quicker to connect) but an F connector gives a

more robust and positive connection, this is particularly important in the case of connections

which require power pass. That said, if your TV or amp has a CoAx input it is pointless putting an

F connector on the end of a cable, then an F to Co-Ax adapter to turn it back into a CoAx. Just put

a CoAx on it, let`s be honest, they`ve been perfectly OK for the last 50 years or so ! If anyone tries

to tell you that CoAx plugs are unsuitable for UHF frequencies or that their impedance isn`t

75 Ohms, believe me they`re talking bollocks. That said, it is true that the fact an F connector is screwed on does mean that the lead is less likely to become detached and furthermore the loss is also marginally lower than for a CoAx. Emphasis on the word marginal though.....

One sign of a good quality Co-Ax plug is if the "claw insert" is brass, as opposed to one of those

horrible shiny metal ones which don`t seem to grip as well. We prefer brass plugs rather than

alloy ones as they are more resistant to corrosion. The alloy ones can become difficult to undo

over time, particularly if the atmosphere is damp or water has seeped down your aerial cable.

It is not advisable to reuse CoAx plugs as the "claw insert" becomes deformed when it is

screwed up onto the cable, they aren`t that expensive anyway. If you have an intermittent signal

it`s always worth checking the CoAx plug as a loose fitting one can cause this symptom, it may

be a low quality plug or it was not even attached correctly in the first place !  Whilst checking the

plug examine it for signs of water/dampness, this is usually caused by a damaged downlead,

see “clipping cable to the slates”. I actually think fitting CoAx plugs correctly is not that easy, so

we supply a leaflet with ours explaining how it should be done. The same applies to F conns.

Alternatively we can attach the plugs for you at a small additional charge, see Custom Cables.

Incidentally when attaching CoAx plugs it is always worthwhile slightly kinking the centre core of

the cable (before you assemble the plug) so as to maximise the chances of good contact

between it and the plugs centre pin. Some people recommend soldering this connection but I`m

not sure it`s really necessary or advisable, it`s probably more likely that you will just melt/deform

the plastic centre spacer rather than adequately solder the centre core !

A better idea than soldering is to lightly crimp (to crimp, posh word meaning to squash) the centre

core of the CoAx plug at the bottom end near the insulator.

We sometimes get people asking us whether they should

use silicone grease on connectors. Well I have to say I`ve

never met an aerial installer who uses it, and that includes

those I know do a good job, and I don`t use it either.

We`ve never been to a job where use of silicone grease

would have prevented the customers problem occurring in

the first place. Oxidation between the cable and the

connector is not a problem, unless you suffer water coming

down the cable. But the latter will also have knackered your

cable plus whatever it`s plugged into.

Worrying about oxidation at the connector is like being

concerned over the flat tyre your car`s just suffered whilst

being written off in an accident !

This thing about silicone grease may be a throwback to the

On the left we have a right angle Co-Ax plug, it IS screened by the way !

Next to it is a conventional CoAx plug, note the brass claw insert.

In the middle is a (male) F connector and a female/female (“back to back”) coupler.

2nd from the right is a male Co-Ax to female F adapter (shown both ways).

Last there is a female CoAx to male F adapter (shown both ways).

(Also see Online Sales / Mail Order Sales including price information)

ATV stock brass CoAx plugs plus "Back to Back" joining barrels to convert a Male Co Ax to a

female. We do not recommend female Co Ax sockets (except right angle types) because the

design of the “in line” type is not conducive to reliability. Very few trade aerial suppliers sell them

either, and that`s got to tell you something

In addition we have "Right Angle" plugs & sockets for use in confined spaces.

Finally we sell decent quality F connectors ( though they are included in any amp or splitter we

sell) and F joining barrels, plus adapters to go from Co-Ax to F connector (male to female and

reverse).

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days when Mast Head (outdoor) splitters and amps weren`t drained and ventilated as well as

most of them are today, ours certainly are. I can`t honestly see why it should be necessary, other

than in a very damp cellar. But if the aforementioned cellar was damp enough to require the use

of silicone grease then you shouldn`t be putting anything electrical down there anyway. And if you

did the damp would have played havoc with the amp or splitter (that the plug is connected to)

long before you should start worrying about the plug !

Some people recommend splaying the screening

strands back over the “claw”, (see picture on the

right) as opposed to folding them back over the

insulation and under the claw, as above.

Theoretically this puts the cable`s screening directly

in contact with the body of the plug. On the other

hand it`s messier, and personally I can`t remember

ever having a problem with the “conventional way”.  

So you pay your money,

and then you make your own mind up.

Do not over tighten a CoAx plug

if you want to maximise the

strength of the claw, i.e. make

it harder to pull off  !

Do not screw up the collar as far

as that in the picture on the left

because the jaws on the claw

are then free to bend outwards.

The plug on the right is

tightened to the optimum with

the collar holding the jaws onto

the cable.

Incidentally, ensure the claws

are actually shaped to grip the

cable, many aren`t.

The ones we sell are.....

The F connector

should be screwed

onto the cable until

1 to 2 mm of the

centre core protrudes

from the top of the F

connector   

We`ve never seen

a decent right angle F connector but we do sell a

right angle F conn

adapter.

Male to Female.

Here we have two types of F Connector.

We stock the one on the right.  

It may be  a little stronger but what is

really worthwhile is the larger nut which

make it far easier to tighten.

Yet again, something so simple......

NOTE !  Decent quality F connectors are included with any

of our splitters, amps or diplexers which require them.