FM switchover.....Coalition steamroller?

[Resurrection Man]

Lat...it's not really down to technology but as Scotty used to say 'Ye cannae beat the laws of physics'.

RF is weird...and why my electronics never really got beyond 4.43361875MHz +- 0.25Hz.

Case in point...when UHF first started, there was a community situated in a valley. On the ridge of the hills surrounding the valley were trees. They only got a TV signal in summer. This was counter-intuitive as leaves on trees usually act as a barrier to RF. Then they chopped the trees down and their signal disappeared completely until a small local relay mast was built many years later. You see, the leaves were acting as a reflector and the UHF signal was bouncing off the underside of the leaves and down into the valley.

[Dave2002]

One suspects that WiFi like BT's service would have similar problems of coverage given that the frequencies used by WiFi are very high [around 1GHz or more so short wavelengths] and so travel badly. Just like a mobile phone network, those WiFi hubs would need trunking to get out of the town to a nearby access point to the main BT national broadband network. All in all expense is involved. I don't know what kind of mobile reception there is in Lynton I don't think LT mentioned it.
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Using ad-hoc moibile networks might just work, with in vehicle units relaying the signals from one to another (and perhaps a few stationary units as well). However this would not be so likely to work in areas with low traffic density which already have poor coverage. It might work on the M25 car park. The normal distance limit for this approach is around 200 metres between units, though there are ways of extending this considerably, but perhaps not within the current legal limits on power.

An idea which was mooted a few years ago but which to me seems to have gone quiet recently was "wireless cities". Again, not really a solution for less populated areas anyway.

[Lateralthinking1]

Lat...it's not really down to technology but as Scotty used to say 'Ye cannae beat the laws of physics'.

RF is weird...and why my electronics never really got beyond 4.43361875MHz +- 0.25Hz.

Case in point...when UHF first started, there was a community situated in a valley. On the ridge of the hills surrounding the valley were trees. They only got a TV signal in summer. This was counter-intuitive as leaves on trees usually act as a barrier to RF. Then they chopped the trees down and their signal disappeared completely until a small local relay mast was built many years later. You see, the leaves were acting as a reflector and the UHF signal was bouncing off the underside of the leaves and down into the valley.

Incredible RM. I live in the second highest place in Greater London. Some say the highest. While Crystal Palace is far further inside Greater London, this is in the same quarter of Greater London as Crystal Palace. I am also not a million miles from Wrotham.

The signal for VHF and UHF television was never a problem, that is for television in London. In fact, in the days of VHF television I could retune the set, move the aerial in the loft, and get Anglia TV in certain weather conditions, albeit hazy. It was an interesting thing to do. I also got Southern but more rarely even though it was closer. Neither though were ever what one could watch for more than half hour. As for UHF, it was easy to get all the main London channels with just a set top aerial.

I don't know if anyone remembers the television and radio end-of-year handbooks in the 1970s that were available from high street shops? They had the television frequencies and maps. I remember that they showed the main transmitters for each area with a big round blob and then there were triangles for all the boosters, eg Brighton where the South Downs create problems. Where was the main one? Heathfield? Anyway, I only scraped a C in Physics O'Level but I've known some of this for a while.

Freeview has always been dodgy here. When I had a set top box, it worked at the front of the house but not the back whereas people three or four houses down the road found theirs worked in all parts of their houses. But then I am not only just under the top of a hill at the back but near a corner. At the front, the hill drops steeply down to a valley road and there is immediately a hill that is equally steep on the other side, almost all of it woods. That is the Crystal Palace direction. The digital television I now have in the front is mainly ok-ish but last night during the prom there was an occasional horrendous sound - like a crackle multiplied by twenty. At other times, some of the ITV stations go down together, all I think on the same multiplex as each other.

DAB radio reception is generally quite good. I couldn't put it any more positively than that though. Channels sometimes have a mind of their own and it can tune out of one and into another. FM has always been extremely variable. Most of it is very good indeed but the reception for R3 has always been atrocious compared with the rest and this seems to be the case whichever direction I place the aerial. Somehow R3 seems that much more sensitive to movement in the house and not in a good way.

So given that this is supposed to be a good location for reception, I suppose I shouldn't be too surprised that there are so many problems in other areas. At the same time we have the hadron collider and missions to Mars - so it still seems a little bizarre!

[Resurrection Man]

.....but the reception for R3 has always been atrocious compared with the rest and this seems to be the case whichever direction I place the aerial. Somehow R3 seems that much more sensitive to movement in the house and not in a good way.

....

I think that this has always been the case for some strange reason. I used to live and work in the South East and R3 was always bad compared to other BBC stations. Bizarre.

Re your Freeview problem, what sort of aerial and downlead do you have? On the problem channels have you had a look at the signal status on your TV? Especially 'quality' rather than 'signal strength'. Freeview can be very sensitive to an indifferent aerial cable. Where I live now, my local transmitter is Ridge Hill and I have direct line of sight. I bought a new external aerial but Freeview was still bad. Then I replaced the downlead cable and it is perfect. So much so that there is sufficient leakage from the plug on the end of the cable that I don;t even have to have it plugged in to the box!

As I said, RF is bizarre.

[mangerton]

I think that this has always been the case for some strange reason. I used to live and work in the South East and R3 was always bad compared to other BBC stations. Bizarre.

It certainly is. I found exactly the same thing from a variety of transmitters in Scotland over the last forty years or so.

[Gordon]

....... I find it difficult to understand how in 2012 these things are technically so difficult so solve.

This is not actually a technical problem although it is not without its difficulties. I can think of several technical solutions to this kind of problem but all would require some R&D and some equipment development, testing and intsallation etc. That translates to the will to do it and to pay the cost and that is where the solution to this kind of problem falters - not enough people suffer in the great scheme of things and resources to fix the problem are not there any more.

Many years ago [in the late 70s from memory but it could have been after Channel 4 in the 80s] the BBC and IBA decided that they had completed the network build for UHF colour TV as required to fulfil their remit to cover a given percentage of population. This meant that some small communities did not get cover either because they were not large enough in numbers to justify a relay or technical difficulties [ie local terrain etc etc] made it too expensive. Then a "consultation" was held about that small percentage of the UK population that did not get service and the result was that it was recommneded that communities of 200 people or more should get it, and surprise surprise government agreed and anctioned the cost! That started an R&D programme that resulted in cheap enough rebroadcast relays [RBRs] and other techniques like passive reflectors [a designed version of the tree leaves that did the job in another posting here!!] and local self help schemes [nowadays solar or wind power would be used as well to energise these small stations]. There was a will then to support community reception and the BBC and IBA were well funded to do the R&D and commission the equipment. Not so now.

One idea that would help in Lynton, and anywhere like it, would be to fit a small single frequency network of micro-transmitters [ie v low power and quite small physically] on existing telegraph poles [BT Openreach permission required - there's century of bureaucratic consultation over the wayleave fee for a start] or suitable rooftops in the town. These would be situated such that they can get a good signal themselves and then re-transmit to serve the nooks and crannies of the town appropriate to that terrain. The BBC once [as did the now long defunct IBA privatised in 1990] had a research dept that did this sort of thing [I know, I used to do it!!] but is now sadly decimated and refocussed onto more immediate issues. There is neither the will, the means nor the money to develop this sort of suggestion and is the consequence of the slow but steady dismantling of public service organisations like BBC and IBA and the slow strangling of their funds and remits by those enemies of anything that is for the public good and not private gain.

In a privatised world Lynton or the like would get nothing at all and be totally forgotten about - not enough revenue to be viable. At least then the good citizens of the town would not be paying a licence fee, however it small it is these days in terms of pence per hour of BBC services.

I would be fascinated to know what the position is in Ilfacombe/Woolacombe as I can't remember what it was like when I was there. Presumably similar if not as bad.

Ilfracombe is close to the same situation as Lynton [and many other locations in the UK] but may be lucky in that Huntshaw Cross or a relay can reach it and cover better although it is still also covered well by the same Welsh transmitters. One would have to suck it and see!!

[Gordon]

....Freeview can be very sensitive to an indifferent aerial cable.

This is one of the most common causs of poor reception in areas where signal strength is supposed to be good. Aerial installers during TVDSO reported that both aerials and downleads were often many years old. If the downlead has an extended section outside it is open to the elements. Its outer insulation degrades and lets rain water through to the outer braided conductor and then into the polythene core which is often not solid providing a path for the water to progress along the length of the cable which is clearly draped so as to direct the water downwards. That water becomes trapped and doesn't dry out. In the presence of damp loss shoots up and the cable is then little better than useless. Oe should replace downlead cables that are exposed every 10-15 years.

[Gordon]

..... 4.43361875MHz +- 0.25Hz.

Now that brings back memories!! What a PAL you are RM and so precise too.

[Resurrection Man]

Now that brings back memories!! What a PAL you are RM and so precise too.

LOL! Ex-BBC myself.

[vinteuil]

my electronics never really got beyond 4.43361875MHz +- 0.25Hz.

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... as a reminder : "The 4.43361875 MHz frequency of the colour carrier is a result of 283.75 colour clock cycles per line plus a 25 Hz offset to avoid interferences. Since the line frequency (number of lines per second) is 15625 Hz (625 lines × 50 Hz ÷ 2), the colour carrier frequency calculates as follows: 4.43361875 MHz = 283.75 × 15625 Hz + 25 Hz."

[mangerton]

One idea that would help in Lynton, and anywhere like it, would be to fit a small single frequency network of micro-transmitters [ie v low power and quite small physically] on existing telegraph poles [BT Openreach permission required - there's century of bureaucratic consultation over the wayleave fee for a start] or suitable rooftops in the town.

While not wishing to decry your idea, which I'm sure would work, would it not be cheaper and easier in these days of satellites for freesat to be installed?

In a privatised world Lynton or the like would get nothing at all and be totally forgotten about - not enough revenue to be viable.

I lived in two Scottish towns which were served by cable systems in the 50s and 60s. One of these (pop c 16,000) was cabled by two competing companies. The cables ran overhead from house to house. I think the weekly cost was two or three shillings!

[Resurrection Man]

While not wishing to decry your idea, which I'm sure would work, would it not be cheaper and easier in these days of satellites for freesat to be installed?

....

Lugging that satellite dish round the garden would be a bit of a drag!

[Dave2002]

Most of it is very good indeed but the reception for R3 has always been atrocious compared with the rest and this seems to be the case whichever direction I place the aerial. Somehow R3 seems that much more sensitive to movement in the house and not in a good way.
!

I am rather surprised at this given your location seemingly close to the transmitters. I agree that generally the R3 signal seemed less good on FM than the other BBC channels, though the dynamic range and audio level (which is usually lower) may have something to do with the perceived quality. I recall that it also actually had a lower measured input signal value from the days when I was able to check that easily.

In what ways is your R3 atrocious? Background hiss, poor stereo, distortion? If it's distortion it could be that you actually need an attenuator in the input line - though this would seem unlikely given that presumably R1,R2, R4 etc. are OK. I found that having a good (very good?) aerial was necessary to get rid of most of the hiss on R3, but otherwise it wasn't such a problem. In Chesham, where I used to live, and where many people have problems because of the valley, reception wasn't generally so good, but as we lived near the top of a hill we did manage to get a pretty reasonable signal, and a low hiss level. That was over a decade ago, and since moving I've not felt so bothered about getting a good aerial in place for various reasons. DAB and FM portables are just about acceptable now for listening to non-critical programmes on R4 etc., and if I feel the need for higher audio quality I tend to use the internet feeds.

At one point I was going to throw away my FM tuner as it seemed to have a fault - also intermittent. Eventually I checked the coax input, and that wasn't set up properly and IIRC had a poor connection. After that it appeared to work fine, though I've still not got round to using it regularly.

One other point, could you be getting other interference? One of my tuners has the ability to change the bandwidth of the IF stages which I believe can improve things in some situations, though I never found it necessary. That tuner also has attenuators built in, and I think it also has a stereo blend feature which might improve the perceived sound in some situations. With a good aerial there wasn't much need for that though.

[Lateralthinking1]

I have read all of today's contributions with interest. Some of the science is a bit beyond me and the rest not so much but I have some further comments on R3 and R4. This is quite difficult for me to explain so please forgive my unscientific language.

Radio 4

With careful tuning, R4's centre point on FM can be found easily. That part of the dial where you know you have hit it spot on.

Tuning a minute distance upwards from there, far less than 1.0 MHz, there is another point at which reception is clear but the volume is lower. That point feels narrower if I can put it in that way. This tells me that it isn't the centre point. I don't know if it comes from another transmitter or whether the location of the nearest transmission offers a narrow band for this area, inside the broader band of 92.5-96.1, rather than just one specific frequency and you then choose which one that suits. It may be that the second is better for North London, for example, and that the first is better for this area.

In between these two points, at the crossover, there is a fade point with minimal distortion.

Radio 3

With R3, there is similar - a point that you know is supposed to be spot on, a point above it which is less so, and a crossover point between the two. The spot on point is far lower in volume than the spot on point for R4 and it is far more susceptible to changes according to aerial direction, room in the house, internal movement and even other electrical devices. In fact, the spot on point for R4 is not susceptible to any of those things. By contrast, it is crystal clear.

The point of lesser reception slightly above the centre point for R3 is flimsier than its equivalent for R4. It is narrower, quieter and quite distorted. At a push, you could listen to off-centre R4 but not easily to off-centre R3.

And the crossover point between the two R3 points, rather than being a simple fade, is a crash of distorted sound.

Just below R3 on the dial - all of R3 - there often appear to be pirate stations from inner South London and that has been the case for many years. They are audible, not that I want to listen to them, but the reception is poor. In fact, it is distorted and seems a bit rangy. I'm wondering if these have an impact on what is happening to R3 reception just above them on the dial?

[Lateralthinking1]

On the TV, and specifically Lynton, my grandparents had Rediffusion in the early 1970s. A dial box on the walls of the kitchen and the living room with a series of letters A to whatever. This might have been the type of service that was discussed earlier and it is arguably a shame that it isn't available now. I don't know how it worked. Was it an early version of cable?

The other thing I wondered was whether it would be possible to transmit the South West of England service from Wales somehow. Can it be done in theory and is the fact that it isn't down to limited capacity of one kind or another? It wouldn't necessarily reach the folks of Winsford and Simonsbath but it would probably solve a lot of problems on the north coast. That would no doubt be welcomed by the majority of hotels in the area as well as the majority of residents.