Ofcon might need reminding about that and the Wenvoe one too. I am sure that they will respond if you ask them.

I once asked them why there was no licence for Teletext Extra (now RadioTimes Extra) and they said because it was part of Teletext. When I explained that it was nothing of the kind and was an Inview product, with its own streams, they promptly made Inview apply for a licence. They never thanked me because they were too embarrassed to admit that they made a mistake.

The radiation pattern imposed on Ch M has the main beam towards the city centre at 135 deg at 1kW and at 120 deg 250W and at 110 deg 10W .
It is the same restriction on each side of the antenna.
Consequently QPSK is the only realistic option to generate any realistic coverage as it provides depending on the code rate and guard interval an additional 6-8dB margin.

The power of 1kW ERP is insufficient for the city due to building clutter as no advantage can be made of the COFDM transmission system which as we all know was designed to overcome such issues as multipath due to building clutter.

Ofcom didn’t issue a licence restricting Ch M to QPSK ,
. The low power and the extremely restrictive TX antenna template was imposed by the planners effectively ensuring they could only operate at QPSK.
In my view this was far too restrictive and I am sure Ofcom would consider relaxing this if a meaningful proposal was made to them.


As to whether local TV can offer spare capacity to other local users to share the costs is a matter for Ofcom and not the planners to decide ,but that seems to be what has been happening.

Which is what I've been saying and that 16QAM operation is bonkers.


But the likely coverage plot, ERP, mode and suitable antenna design was clearly stated in the prospectus. Why should Channel M get more free spectrum because they want to make more money from it? A similar radiation pattern etc appears in the new local TV proposals for Manchester using a 500ft antenna. Surely QPSK was proposed & used to counter the high power adjacent channel and is the correct mode to operate in these conditions.


I wasn't referring to sharing the capacity, but sharing the new antenna, so that the two low power signals aimed at Manchester are of similar strength and coverage.

Show me where it states the TSA in the licence. If a TSA was clearly indicated, and they were trying to increase that area, then there would be an issue. However, if they could prove that the technical parameters of the licence didn't allow them to cover the TSA, then there wouldn't be an issue to them requesting Ofcom to alter the parameters to suit, assuming of course it doesn't cause increased interference with other services. I know numerous radio stations have been able to prove this in the past, and many have been successful in their requests for antenna/power improvements.

All I can see in the way of restrictions is an interference template, if they can prove that they won't affect that template with the changes they want to make, there should be no impediment, legal or otherwise, to them doing so.

I don't know where this 'here it is, take it or leave it' attitude that you think Ofcom should take, is coming from. You might not think that's fair, but I honestly can't see the issue with them trying to improve their situation, if doing so is perfectly legal.

All I am saying is that QPSK operation works adequately in the circumstances. In DVB-T that means a maximum of 3 TV channels and Channel M should accept that. Obviously I do not have detailed reception figures but many Gtr Manchester DS posters used to be able to receive the mux before it changed to 16QAM. Maybe Channel M should try DVB-T2 if they can afford it, which using QPSK at 3/4 code rate allows 11.2Mbps or enough for 5 SD channels. Perhaps like the NI mini mux, 16QAM DVB-T2 operation would be viable with a higher margin to adjacent channels and an even greater mux capacity.

The licence does not appear to be available to the public and so we are relying on posters with privileged knowledge of the issues.

I believe all the relevant terms and restrictions are in the Information Memorandum that was published by Ofcom prior to the awards.

But that included an antenna at 500ft which is not the case today when it seems to be at 100ft. I do know that Ofcon are very fussy about antenna heights in licences.

Licence #0313145. The FAQ on that site suggests that Ofcom will respond to queries about licences from potential transferees, so you could always ask them.

Having checked back with the DCMS local TV proposals for Winter Hill, I see that the Manchester segment is illustrated with both 1kW & 2kW ERP proposals. If that is right and the local TV gets 2kW then obviously Channel M should also be allowed 2kW.

Sharing the antenna is not a option unless the restriction template is identical on ch 56 and 57 .
I do not believe it is.

Also the cost of adjacent channel combiners are very high unless a different transmitter configuration is utilized.

What this debate seem to be about is can ch M utilize the capacity in bandwidth terms that their licence permits them to.
If improvements in coverage can be achieved at the same time as increasing capacity in the mux to offer some to others and if this is in the terms of the licence issued by Ofcom in my view there shouldn’t be an issue.
Ofcom have stated that the only restriction on this licence is the restriction template consequently ensuring there is no interference at all to other relays or main broadcasts, that is my understanding..

Licence terms may be different on other RSL,s

Also in order to improve capacity and coverage if a application is made at some stage to Ofcom to relax the restriction template or amend the transmission parameters because of unforeseen technical impediments to coverage at the time the licence was issued and it can be shown that this doesn’t increase the risk of interference to others .
It is Ofcoms decision and not Arqivas and a normal procedure.
Arqivas role is to supply technical input and this should not be biased in favour of Arqiva especially as there is a possibility of a conflict of interest

The important thing is everybody plays by the rules and that includes Arqiva.

Surely an antenna comprised of log-periodics which fires a beam at Manchester city centre would be able to share. I take your point about adjacent channel combining.

Log antennas are the worst possible choice for this particular application to maximise coverage using the restriction template.

A huge improvement in coverage can be achieved if panels are used as this will increase the 3dB points compared to a stack of four logs by approx +/- 20 deg.

You must have noticed multiple panel arrays are now the preferred choice for DVB-T broadcasts.

One of the major technical issues all engineers have had to consider is the nulls in the horizontal plain,in particular with problems with the cliff edge effect..

In a typical 360 deg configuration in particularly at the top end of the UHF band the radiation pattern has nulls of -4dB approx every 30deg with a 4 panel per bay array..

The pattern is a bit like a clover .
Consequently if there is a high power mux on the next channel and the margin between the two is only 3dB ,reception is then compromised at about each 30 deg point .

Using multiple panels in each bay as the PSB muxes have at Winter hill reduces the nulls considerably

Using logs in array and trying to create minimal nulls and the required beam tilt to fit into ch m,s template restrictions (75-165 deg), in my view is impossible and consequently the radiation pattern is compromised.
Consequently coverage at 16QAM is restricted more than it needs to be.

Panel arrays would provide at +/- 20 dg a flat pattern within ½ deg. This makes a huge difference and also the 3dB points of the radiation pattern are improved by at least an extra +/- 20 deg that could be achieved with logs.

When I discus the stupidity of using logs with other engineers for main transmitter sites ,comments like numb nuts and moronic is often made.

Logs are only useful in very low power situations and a narrow radiation patterns is needed with no or little beam tilt ,or a v shaped or a specific pattern.
Crossing the log antennas has to be done to minimise the nulls.

I am not aware of any other country in the world who has such a love affair with log antennas for transmission as the UK.

As a low cost alternative to panels in narrow pattern application and with better back to front ratio than a yagi ,I sometimes can see the point were logs are usefull.

But to specify logs on Ch M ,s coverage is in my view grossly incompetent.
But that is my opinion!