Hillsborough
Sheffield
S6 2LL
All Rights reserved
Main Page List
Tel : 0114 285 4254
Con trails over Oughtibridge / Wharncliffe repeater transmitter.
Oughtibridge TV transmitter against the setting sun.
Graphic showing the use of a repeater / relay transmitter to improve coverage in a valley which lacks the all important “line of sight” from the main transmitter.
Note that the Emley Moor transmissions are shown in yellow (B group) and the Oughtibridge transmissions in green (for C/D group).
Nearly all repeaters will transmit digital within the same group as their
analogue broadcasts, i.e. your existing aerial will probably work fine.
Close up of a repeater transmitter`s aerial array, this is Oughtibridge and it is a good example of a smaller repeater.
A repeater (or relay) is a transmitter which receives a signal from a main TV transmitter, remodulates it onto a different set of frequencies and then rebroadcasts it again. There are about 1105 * of these in the UK , of which 30 are larger repeaters (like Sheffield). A full list of the analogue transmitters can be found on the BBC website, or, for the digital frequencies, Ofcom pre DSO / post DSO or Digital UK (use the drop down menu to change the region).
Repeaters are used to transmit into areas which are unable to receive good signals from the main transmitter. Although most repeaters only broadcast to a relatively small number of people the larger ones can have significant coverage with a tens of thousands of houses receiving from them. In the case of Oughtibridge the repeater retransmits into the low lying areas of the Don valley around Wharncliffe and Oughtibridge, hence the name. The signal is received from Emley Moor (situated to the NW) using the log periodic at the bottom of the picture and then rebroadcast via the Log array at the top of the mast into the valley to the South and West.
Repeaters are usually vertically polarised, but about 70 are horizontal (e.g. Dronfield). Although this represents around 7% of all repeaters the larger ones (which transmit to far higher numbers of people) are all vertical, thus probably 99% of people on repeater transmitters would have aerials vertically polarised, assuming the aerial`s correctly polarised.......
Note. Many repeaters have restricted radiation patterns (see that for Oughtibridge below) and appear to be low powered.
At DSO (Digital Switchover) the plan is that these smaller repeaters will only broadcast the three PSB MUXES, not all six of the MUXES. That will still give all the five channels which are presently transmitted on analogue, plus a load of others, plus three or four HDTV channels.
But you won`t get all of the available transmissions off a smaller repeater, to do that you`d need to get on a main transmitter *.
I wouldn`t worry about not getting all the channels though, most of the extra channels are repeats (or rubbish) anyway.....
* Source Ofcom Nov 2008 (excludes “self help” transmitters).
* Getting your signal from a main transmitter should be significantly easier when the transmission power is increased after digital switchover.
These aerials are of BBC design but manufactured by Chelton electronics.
They are 48" long by 13" wide, with 30 elements and a gain of 6 to 8dBd.
These must be the most ruggedly constructed aerials around and are generally used for broadcasting but also by the military. And they should be well made, because they weigh nearly 3kg, and cost over £500 each ! ? !
Details N Savin 2009
Close up of the receiving Log Periodic aerial at Somersham repeater transmitter.
BBC research department pdfs :
Note the broadcast authorities use of Log Periodic aerials (see below). They use them wherever possible, we use them wherever possible, and so should everyone else !
Oughtibridge Transmitter OS Grid Ref SK 307 952
Note, as work takes place on various digital transmitters (to prepare for the DSO) you may experience problems, e.g. with certain MUXES disappearing. First try rescanning your TV / set top box (do it manually if possible), but if this fails to work check on transmitter workor call the reception advice phone numbers. Also see basic digital fault finding.
Switchover occurred at Oughtibridge between the 7 and the 14 of Sept 2011.
Subjects are listed on this page in the following order :
Oughtibridge Transmitter including low power digital transmissions, or not ?
Transmitter radiation pattern for Oughtibridge transmitter.
Note how the transmissions aren`t Omni directional.
Graphic courtesy of Mike Dimmick.
Oughtibridge / Wharncliffe television transmitter was opened in 1980 and broadcasts into the Upper Don valley. It is necessary due to Emley, Belmont and Crosspool transmitter`s being hidden by the hills. It is a relay of Emley Moor and is a Vertically polarised C/D group of 8W. Now 8W might not sound a lot in comparison to a main transmitter, or even the 39W it used when broadcasting analogue, but, for Oughtibridge, in a way, it`s a power increase !
How can a power increase be a power decrease ? ! ?
Well at our test site directly across from Oughtibridge transmitter, a DM log used to average 60dBμV, for analogue. The figure would vary from day to day, but not by that much.
For digital the DM log gives about 54dBμV. But........
The recommended signal level for analogue reception is/was 60 to 80 dBμV, so the received signal was at the bottom of the range.
However, for digital the recommended signal range is 45 to 60 dBμV, so the received signal is now at the top of the range.
So, in a manner of speaking, we get a signal increase for a signal decrease.......
The same applies to the main transmitters. From the test site Emley`s 870kW on analogue gave an average of 87dBμV, but now, with digital transmitted at 174kW, a DM log gives about 81dBμV. Before, the received analogue signal was 7dBμV over the recommended level, but now the lower power digital signals are 21dBμV over recommended !
Also note the power decrease to dBμV readings. For a signal power level approximately one fifth we get a signal drop of 6dB.
As with most of the smaller relays only MUXES 1 to 3 (the PSBs) are transmitted from Oughtibridge, not all six.
The original plan was for another 200 of the larger repeater transmitters to broadcast all 6 MUXES, but the commercial broadcasters declined to pay for it !
In this area we would put customers on Emley where ever possible (for reception of
all 6 MUXES) but as one drops down into the valley this becomes more problematic.
However, if one examines the topography map some people have a view NNW up the Don
valley and so can still get onto Emley even if they live on the valley floor. The
mast is quite well hidden behind Wharncliffe Woods but if one looks closely one can
just see the transmitting array of Log Periodic aerials above the tree line. The
Channel Allocation Guide reveals that all 3 channels are transmitted on the same
frequencies as both Wincobank and Dronfield repeaters, though one would not normally
get any co-
A single track stub of the ex Great Central Railway (which originally linked Sheffield to Manchester via the Woodhead tunnel) runs in the valley below. These days it only sees one train a day running from the steel works at Aldwarke to the plant at Stocksbridge. How the mighty have fallen, back in the 1840s this railway was one of the first main lines built in this country and it was electrified at great expense (and six men`s lives....) in 1954.
External Links
Oughtibridge transmitter page at MB21
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.
If you`ve found this site informative and, hopefully, interesting as well,
please help us increase the number of people reading it.
