Hillsborough
Sheffield
S6 2LL
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Main Page List
Cable, Connectors and Leads (Also see Online Sales / Mail Order Sales)
Subjects on this page are listed in the following order :
The Importance Of The Cable And The Routing Of It (including Surface Plates ,
Cable Through Your Window Frame and Clipping Cable To The Roof Slates)
The Three Main Types Of TV Aerial Cable
H109 / CT100 Type Satellite Cable
“ Hole Tidy” (installed in a sheet of Perspex) “Blow Out” cover
Their matt finish means they`re ‘paintable’
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 !
If your downlead is cut through, best practice is to replace the lot. It may be budget
Co-
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 sending 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 and any
wind movement can cause the downlead to bang against the inside of the tube in a most annoying fashion.
Whilst routing downleads do not introduce sharp bends or kinks to them and if you are splitting it always use an amp or splitter (as 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 amplifier).
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 !
If you accidentally damage the brickwork, whilst drilling the hole through the wall, we sell “blow out covers” in brown or white. Incidentally these are just to cover up any “blown out” brick work, they aren`t used to prevent water ingress, you should silicone the hole and use
a “drip loop” just before the cable enters the wall to achieve that.
When a cable is routed across a roof it should be clipped to the roof slates at regular intervals (use a short length of a few strands of galvanised lashing wire bent into a “U”) to prevent it moving in the wind and being worn away by the slates, see picture. 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.
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 then seeps 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.........
The picture on the left is of a “slate clip” which is
simply a few strands of galvanised lashing wire
(as found in the lashing kits we sell) cut to around
six inches, then bent into a “U” and wedged under
the slates to secure the cable.
The Three Main Types Of Co-
All TV downlead should be 75 ohm in order to maintain an "impedance matched system"
but there are 3 main types of cable and they are listed below.
Traditionally everyone used "Low Loss Co-
"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-
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. Most new build houses use ultra cheap Co-
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" Co-
This is the lower quality grade of satellite cable, but even the cheapest is far
better than "budget low loss" Co-
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 minimise 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, I would say that it`s adequate for
most satellite use provided the down lead is not of excessive length.
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
H109 / CT100 Type Satellite Cable
The third type of cable also has "double screening", but this time the additional foil is copper (see picture above). 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 TV/DAB/FM (i.e. UHF/VHF) but being a perfectionist I like that. The price difference on a typical 15m run is only a few pounds, so why not fit the best ?
It is also suitable for all satellite installations 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 it can`t run down into
your TV as easily as it can with air spaced !
This CT100 type cable is the only grade we sell in Black, White or Brown at 55p per m,
or by the 100m drum for £45. In addition we stock 50m reels (in Black only) at £25.
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
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 we would be happy with (the ultimate recommendation ! ), is acceptable.
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-
We also stock weatherproof joint boxes but “spare” cable is needed to route into/out of the enclosure at the bottom and in addition to this they aren`t screened. If joining cables of different diameter they can be useful however.
We don`t really recommend surface plates, but if you have no choice but to use one, try to ensure it`s screened (as in those above) and that the cable is not kinked. Route the cable like the one above right and not like the other one...... (see surface plates incl diplexed)
We are more than willing to give advice to those actually purchasing from us.
Could those only seeking information please just ring an aerial installer local to them or try calling reception advice on 08700 100 123 (BBC) or 0844 881 4150 (ITV).
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-
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 do not recommend the use of surface plates in the wall particularly 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. We advise utilising the cable direct from the aerial straight into your TV or Digital/Freeview box.
If you have one of the latter the cable should always go into that first. Placing
a "hole tidy" (sometimes called a cable tidy or grommet) around the cable just where
it enters the house provides a neat job (see picture) and it`s quicker / cheaper
than a wall socket. We have had customers complaining of poor signal 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-
It is actually”double screened”
in that the individual signal wires, (e.g. Video) have a screening foil and there is a second outer screening foil over the whole bundle. The grounding for the latter can be seen emerging from the bundle and leading
to the “spade” connector.
This grade of cable is also
known as “U Type”.
We sell these cables in
1m, 3m, 5m and 10m lengths.
SCART Leads And Phono Leads
SCART leads were introduced by Philips (as "Peritel") 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 it`s component parts of Video + Audio (left) + Audio (right). In addition a switching voltage is sent over the SCART lead which automatically switches the TV connected to it 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". Speaking as a TV engineer I dislike any "auto function" system (including "auto tuning") and also "user friendly" menus, which in my experience are anything but. The switching voltage can be disconnected by carefully pushing pin 8 (of the SCART) back into the plug head or by cutting the wire to it. Other signals and voltages can also be sent/received but these are beyond the scope of this article.
The big advantage of using SCARTs (rather than modulated signals at RF through the
tuner) is that the risk of co-
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 don`t cost that much more than "budget overall screened" types. These only have a screening foil around the whole bundle of wires and
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 up to 10m !
ATV sell individually screened SCART leads in lenghths 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/Videos but are also used on Hi Fis and some other audio visual products in
this country. We can supply Phono leads (and Phono to SCART adapters) if required.
(Also see Sales / Mail Order Sales including price information)
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 over as often as you would think.
ATV sell 3 way manually switchable SCART boxes.
(Also see Online Sales / Mail Order Sales including price information)
If you have a wall socket (which we don`t recommend) then you need a lead from there to the set. Also the same is required to connect up your Video to the TV. These leads are relatively cheap so make sure you buy a decent one. If possible it should have double screened cable and just as importantly the plug should be crimped to the end (see below), rather than just moulded on with the centre core soldered. 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 quality double shielded cable and, just as significantly,
utilise crimped on plugs, they are £2.50 for a 2m and £5 for a 4m.
To be honest these leads are probably the biggest bargain we sell and I can`t understand why we don`t sell 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 -
open to show the joint and took a picture, so here it is.
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 “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
The Co-
An F connector is usually only fitted on a satellite lead (from the dish) and screws onto the STBs socket.
Push in Co-
obviously ! ) but it is very bad practice to use Co-
damp or water has seeped down your aerial cable. It is not advisable to reuse Co-
Co-
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 Co-
see Custom Cables. Incidentally when attaching Co-
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 !
On the left we have a right angle Co-
Next to it is a conventional Co-
In the middle is a (male) F connector and a female/female (“back to back”) coupler.
2nd from the right is a male Co-
Last there is a female Co-
(Also see Online Sales / Mail Order Sales including price information)
Here we have two types of F Connector and
we used to stock the type on the left until we
discovered the type on the right. It may not
look that different but it is. It`s probably a
little stronger but what is really worthwhile
is the larger nut which make it far easier to
tighten. Yet again, something so simple......
Co-
ATV stock brass Co-
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-
(Male to Female and reverse).
NOTE !
Decent quality F connectors are included with any of our
splitters, amps or diplexers which require them.
Note, we now stock a superior type of F Conn at 75p (or 50p ea for 5+).
Routing Co Ax Next to Main Cables ?
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 Co Ax, 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 of 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 Co Ax, and I have to tell you there was no detectable interference with that either. That said, I have heard of cheap Low Loss Co Ax introducing RF crosstalk to adjacent cables when bundled together, but this obviously isn`t at 50Hz main frequency
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 Co Ax. Far more likely would be unscreened splitters, amps or surface plates.
Having said all of the above, I`d still only route Co Ax cable next to mains cable if you really had to, and I`d make sure it was satellite grade as well.......
Picture of cable bundle exiting the tubing, then supplying the signal to the TV, just behind it.