Hillsborough
Sheffield
S6 2LL
All Rights reserved
Main Page List
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
Alloy Foil Type Satellite Cable
Copper Foil Type Satellite Cable
Routing Mains Cable Next To Co Ax ? (and electrical interference generally)
“ 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 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.
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)
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. 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-
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 and this is particularly 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. 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.
“Low Loss” Co-
(note the low percentage
screening cover,
and some examples
are significantly
worse than this....)
Alloy foil type
“satellite cable”
(note the presence of an additional aluminium screening foil)
Copper foil type
“satellite cable”
(note the presence of an additional copper screening foil)
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” which is simply a few strands of galvanised lashing wire (as found in our lashing kits) 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 coaxial cable and they are listed below.
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 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, I would say that it`s adequate 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-
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 )
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 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.
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. 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.
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.....
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
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 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
that in this test 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, 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 Co Ax 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/copper type satellite cable.
Picture of cable bundle exiting the tubing, then 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 Co Ax 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.
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 Co Ax 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.......
Freeview picture whilst under test
with satellite cable
Freeview picture whilst under test
with “Low Loss” cable
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 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).
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. 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.
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-
socket on the TV, or Set Top Box, or Amplifier / Splitter (see Picture).
An F connector is usually only fitted on a satellite lead (from the dish) or a mast head amp down lead and screws onto the STBs socket.
Push in Co-
obviously ! ) but it is very bad practice to use Co-
Co-
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
Co-
it back into a Co-
the last 50 years or so ! However it is true that the fact an F connector is screwed on does
also mean that the lead is less likely to become detached.
One sign of a good quality Co-
is usually caused by a damaged downlead, see “clipping cable to the slates”. I actually
think fitting Co-
when attaching Co-
A better idea than soldering is to lightly crimp (to crimp, posh word meaning to squash)
the centre core of the Co Ax plug at the bottom end near the insulator.
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.
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-
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 SCARY 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.
(Also see Sales / Mail Order Sales including price information)
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.
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, which is a high
gain type. 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
capacitors (3nF at 3kV) were shorted out most (but not all) of the attenuation disappeared.
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-
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" Co-
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.
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 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 at 50p per m,
or by the 100m drum for £42.50. In addition we stock 50m reels (in Black only) at £22.50.
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 )
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-