4G and Freeview

[Don Petter]

DAB is so easily, and seriously, compromised by mobile telephone transmission sites. Every time I drive past one the DAB gets disrupted. I first noticed the effect when passing the transmitters adjacent to Ashford Hospital, but have since encountered it when passing a similar mobile telephone aerial profusion nearer to my home.

I've had no trouble like this since I started using an external car roof aerial - near continuous 100% signal with very few intermittent dead spots, usually among buildings in the centre of big towns.

[Gordon]

I've had no trouble like this since I started using an external car roof aerial - near continuous 100% signal with very few intermittent dead spots, usually among buildings in the centre of big towns.

Gone quiet over here hasn't it, after all that spleen!!

A car is a Faraday shield so anything other than an external aerial is going to be a compromise. You are probably using the best there is in the circumstances, a roof mounted monopole of a length close to a quarter wavelength [about 340 mm for DAB 750 mm FM] that is able to use the roof metal plate as a ground plane, assuming your car hasn't got a plastic roof like some have these days and also that there isn't a big hole where the sunroof is. Aesthetic considerations means that most cars have very much less than optimum aerials, sometimes hidden away or stuck to the window glass like a heated rear window element which it often is as well!!

Add some interference to a poor aerial and you get trouble as Bryn has experienced around Ashford. I'm not convinced that Bryn's problem is a mobile phone mast although it is not out of the question if there is a bit of "rusty bolt" around somewhere.

http://www.google.co.uk/#hl=en&output=search&sclient=psy-ab&q=rusty+bolt&oq=rusty+bolt&gs_l=hp.3..0l8j0i10j0.1234.4031.1.4172.12.11.1.0.0.0.407.3188.2-4j5j1.10.0...0.0.354HTKT469M&psj=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=6fce60427945059e&biw=1093&bih=827

Most likely is some strong radio source emitting in the VHF around the DAB band frequencies that gets into the front end and blocks it momentarily. Mobile phones do not operate anywhere near Bands 2 [FM] or 3 [DAB], they are all above the DTT band V starting around 900 MHz and going upwards. VHF radios in the hospital however,.....

[Don Petter]

A car is a Faraday shield so anything other than an external aerial is going to be a compromise. You are probably using the best there is in the circumstances, a roof mounted monopole of a length close to a quarter wavelength [about 340 mm for DAB 750 mm FM] that is able to use the roof metal plate as a ground plane, assuming your car hasn't got a plastic roof like some have these days and also that there isn't a big hole where the sunroof is. Aesthetic considerations means that most cars have very much less than optimum aerials, sometimes hidden away or stuck to the window glass like a heated rear window element which it often is as well!!

Good deduction Holmes!

Mine is a quarter wave with magnetic base, mounted centrally about a foot forward of the rear edge of the estate car roof. (It's about five feet away from the rear of the sun roof aperture, but with the longest lead I could find (2m) and feeding it along inside the trim and then up from the centre rear, I can't get it any further forward.)

[Gordon]

Elementary my dear Watson! You might do tad better with the magmount a bit further forward but not much. The proximity of that back edge along the top of the rear door will have a small effect, probably only when the transmitter is behind you. An estate has a good ground plane roof area compared to a saloon say.

What is affected more is not so much the signal collecting capacity of the aerial [the Gain] but its directional features [its horizontal polar response, HRP] which is rather important in a vehicle that alters its angle with respect to a wavefront coming from a transmitter. You don't really want to turn a corner and have the radio die. Putting an amplfier in the lead will not change the HRP. Some of the simple window mount aerials do just that and have some awful polar responses with deep notches caused by door pillars etc not to mention poor impedance matching both to space and the receiver input. Monopole magmouts are best. One of the worst aerials I've seen measured was from a well known up market executive brand that has 3 letters and comes from south Germany.

[Bryn]

The thing is, I get the same problem when I pass what is definitely a mobile phone transmission aerial site about half a mile from my home. It's not a route I often take with the radio on, so had not noticed the effect there until a couple of weeks ago. Admittedly I do have a windscreen DAB aerial. I suppose there could be an emergency services FM repeater in addition to the mobile phone transmitters at the local site. I will have to check.

[Dave2002]

Since this is all about radio frequency spectrum constraints, I hope it hasn't escaped your notice that, in the case of BBC broadcasts and many other radio stations, they're available on:

FM
DAB
Freeview****
Freesat

Radio 4 is also available on LW

**** Seemingly not in Scotland, much to my surprise on a recent trip to Dundee. We were unable to access Radio 4 using Freeview. TV channels were available.

[Northender]

I think access to a number of radio stations is restricted in Scotland in order that BBC Alba can be accommodated on the Freeview platform. (Freesat enables me to watch certain Rugby Union matches on BBC Alba, and S4C, while understanding about 1 word in 10 of the commentary.)

[Dave2002]

I don't have a problem with Scotland having BBC Alba, but that does make a mockery of the claim that National radio channels are available on the Freeview digital platform. Of course, if Scotland votes to go it alone ...

[mangerton]

I don't have a problem with Scotland having BBC Alba, but that does make a mockery of the claim that National radio channels are available on the Freeview digital platform. Of course, if Scotland votes to go it alone ...

Dave "National" radio stations which are available on "other platforms" (eg FM radio, DAB, t'internet) are not available on Scottish freeview between 5 pm and midnight Mon - Fri, and (I think) 4 pm and midnight at weekends. This is to release bandwidth to allow BBC Alba to be broadcast, as Northender said. As you found out, it's a pita, even in Dundee and other large cities where FM is available. It's even more of a pita in some remote parts of Scotland, where the only way to get these radio stations is via Freeview.

That said, I was appalled to note when spending a night recently in a (large chain, overly expensive) hotel in Bristol, the only radio stations available in my room were Radios 1 and 2. Fortunately my mobile phone with FM radio was to hand.

[Dave2002]

mangerton

Thanks for the clarification/update. I think I was trying to hint that some in the south of England, e.g Vaizey, may not know this, and will chunter on about digital platforms and takeup etc., when the reality is that some basic services are not available in some parts of our nation, as it is currently constituted.

Probably similar to Mrs T's views on trains, since AFAIK she hardly ever used them.

[Anna]

Where I am Freeview offers BBC1,2,3 but inexplicably not BBC4. ITV1,2, C4, C5 and S4C. Radio is just BBC Wales and BBC Cymru. Therefore I have FreeSat as I watch a lot of BBC4 and it enables me to get the whole range of radio programmes. So, Freeview does vary considerably in what it offers according to location.

[Dave2002]

Where I am Freeview offers BBC1,2,3 but inexplicably not BBC4. ITV1,2, C4, C5 and S4C. Radio is just BBC Wales and BBC Cymru. Therefore I have FreeSat as I watch a lot of BBC4 and it enables me to get the whole range of radio programmes. So, Freeview does vary considerably in what it offers according to location.

I guess those "in charge" or possibly responsible for a future digital radio switchover, would like to be able to plead ignorance of this. Surely Radios 1 through 4, at a minimum, should be available on all digital platforms, including Freeview, in order so support any possible claim that digital listening outnumbers listening via FM. This is an argument which has been invented by some who have vested interests in turning off FM. I'm not so anti turning off FM myself, but the digital or other alternatives do need to be at least as good and widely available with similar or better levels of service.

[Anna]

I guess those "in charge" or possibly responsible for a future digital radio switchover, would like to be able to plead ignorance of this. Surely Radios 1 through 4, at a minimum, should be available on all digital platforms, including Freeview, in order so support any possible claim that digital listening outnumbers listening via FM. This is an argument which has been invented by some who have vested interests in turning off FM

But, DAB radio where I am is a non-starter (maybe possible with new large aerial installations?) so I am reliant on my FM radio for everyday listening and whilst I can go in the room where the tv is to listen via FreeSat (not convenient as a large part of my listening is in the kitchen/dining area) or listen via the computer (with a not very brilliant sound and again not convenient) I want to able to listen in any room I choose, hence my portable Roberts which also gives me LW (for Radio 4 Cricket) plus MW. Therefore, until they sort DAB out an FM switch off would be a disaster for me and many others. It's really annoying that it's presumed (by those in London) that everywhere has blanket coverage, rather like the assumption that everyone has a computer and therefore iplayer is available to all.

[Northender]

I guess those "in charge" or possibly responsible for a future digital radio switchover, would like to be able to plead ignorance of this. Surely Radios 1 through 4, at a minimum, should be available on all digital platforms, including Freeview, in order so support any possible claim that digital listening outnumbers listening via FM. This is an argument which has been invented by some who have vested interests in turning off FM. I'm not so anti turning off FM myself, but the digital or other alternatives do need to be at least as good and widely available with similar or better levels of service.

A friend of mine retuned his Freeview set the other week, whereupon he regained some of the channels he'd lost on the previous occasion and lost others which he'd gained on that occasion.

[mangerton]

Where I am Freeview offers BBC1,2,3 but inexplicably not BBC4. ITV1,2, C4, C5 and S4C. Radio is just BBC Wales and BBC Cymru. Therefore I have FreeSat as I watch a lot of BBC4 and it enables me to get the whole range of radio programmes. So, Freeview does vary considerably in what it offers according to location.

Anna,

It looks to me as if you're missing at least one multiplex - possibly more. BBC 4 is broadcast on a different multiplex from the other BBC channels You should also get the BBC news channel, two BBC children's channels during the day (these share multiplex space with BBC3 and 4, so disappear in the evening). You should also get a lot of commercial rubbish which you probably don't want. Perhaps a retune would help. Try that and see. Do you know what transmitter you use? It's probably Wenvoe or one of its many relays:

http://www.digitaluk.co.uk/when_do_i_switch/wales/wenvoe

If, like me, you use a relay, you won't get as many multiplexes, and therefore stations, as those using main transmitters, but you certainly should get the public service multiplexes which include BBC4. This, by the way, is a nasty form of discrimination which has been sneaked in via a back door. We all pay the same licence fee, but those of us using relays get a much inferior service.