75kHz FM plus DAB DX

[Pye Man]

All you need to know from Halfords:

https://www.halfords.com/advice/technolo...uide-video

I've taken a screen grab for posterity and to add to my technical library.

[ppppenguin]

Buzz!

Deviation.

Challenge allowed.

You have 48 seconds on FM vs DAB.

[Mike Watterson]

Oh dear.
Words fail. Also AM is nothing like FM, though my 1929 and 1935 AM sets sound better on R4LW than RTE1 does on DAB! Probably big box and speaker vs 3.5" speaker and plastic box.

If the DAB used 256K I'd believe better quality. Not at 128K MP2 and 64K AAC.
Also 220MHz is worse coverage than 100MHz. There are not enough fill in masts for portable or car coverage for DAB. That's why they do opt-outs on R4LW.
Here the DTT is in theory worse still coverage being 470 to 750MHz approx, except here DAB has  less than 50% geographic rollout and DTT is 99% with also Ka band FTA sat coverage. Also most of the DAB here is only RTE plus a few extra semi-automated RTE, all on DTT.
Also a DTT stick for a tablet or Laptop uses less power than DAB and is about £7 inc postage.
FM receivers use even less power.
Outside of a car I've not seen a single DAB set that is has a decent speaker.
Sadly the DTT here uses the same 128K stereo as the DAB.

I  have a satellite distribution system for non-Irish stations. A £35 Sat receiver and £5  FM transmitter intended for MP3/Phone to car radio (CE) is used for up to three extra stations. The quality on any decent FM portable or table model (home, car in drive, or workshop) is superb.
I get about 10 to 20 FM stations on my phone too, not just RTE. ALL far better quality. BECAUSE the bitrate is to low (worse for poor hearing as the 128K MP2 assumes a standard hearing) and coverage too poor.
The ergonomics on modern portables is mostly ghastly, though worse for FM than DAB.
Channel change time to a different Mux? Terrible in N.I., no problem here as there is only the RTE mux.

Now they are practically giving away top of band one. 67MHz to 87MHz and 175 MHz to 195MHz would have made more sense for Rural/National and local/community FM. I even have DOMESTIC sets that do those bands.

DAB was too early and now the operators are too greedy. Halve the number of stations per mux and add far more masts and develop a cheap low power chipset, then I might take it seriously.  The DAB+ is simply being used to increase the number of stations, not quality. South East DAB+ here is all 64K!

[radioman]

You're lucky ! - many DAB+ stations here are only 32k!!
The DAB radio in my car suffers from drop-out due to the terrain whereas the FM signal does not. However, I suppose having the aerial built into the heated rear window doesn't help...

Andy

[ppppenguin]

The odd thing is that early work on DAB showed a lot of promise. I remember going to a talk at the IEE some years ago where BBC Research showed a film about their DAB work. They had a equipped a coach with FM and DAB receivers and set up an experimental DAB TX in Birmingham. They drove the coach around Brum's tunnels and underpasses. DAB stayed rock solid except in the longest tunnels, FM was pretty horrendous.

That's the RF side. I don't know what got downgraded between the tests and start of service, or if for some reason the tests weren't representative of real life. I don't believe that BBC Research frigged the results. Perhaps it's a bit like the introduction of VHF FM in the 1950s, where the assumptions were wrong for hjow the service actually developed. For VHF FM the service was predicated on the use of outdoor aerials, just like TV. Needed more power and mixed polarisation to get it work well with portables. Should be posible to find the relevant reports on the BBC Research website.

The audio side is another matter. I think DAB was conceived with 256kb/s and MP2 data compression. I understand this is pretty good but as you push down the bit rate then MP2 is far from ideal. It was too soon for MP3, AAC or other data reduction which can give better results at lower bit rates.

So we're saddled with a half-a****d system. What's the betting that FM will outlast DAB? With internet now being an important platform for radio what's the real point of DAB?

[Old Sparky]

I admit that I seldom use either of my DAB radios (both portables) now, as I either listen via Freeview or on the internet, though I sometimes listen to Radio4 Extra on DAB, and, for speech programs, the quality is O.K. In fact I'm often amused when the continuity announcers apologize for the quality of the mostly 50 or more year old programs the station broadcasts, forgetting, perhaps, that most people in the 50s & 60s listened to MW or LW anyway.

[Pye Man]

Apologies! I didn't really want this to become a discussion of of DAB versus analogue as I know this subject is often contentious and the arguments well-rehearsed.

Perhaps it's how I read it but I was rather amused by the copywriting that referred to the 'super-fast wavelength of around 220MHz' and implied FM broadcasts on 75kHz - I have missed out on these but am just thinking about the length of a whip aerial on a portable for the latter!

And also 'you'll be able to listen to [DAB] channels from all over the UK (and sometimes even abroad), rather than local broadcasts on FM / AM'. I know there's been a bit of a VHF 'lift' recently but I've yet to log my first continental DX on DAB! As for 'all over the UK' I'm a bit disappointed that although Radio Caroline is on a small MUX in Birmingham the best I have managed is to get an indication of its existence on the screen but not a squeak - not even 'bubbling mud'. Perhaps I've got the wrong sort of receivers but I seem much more likely to hear broadcasts from all over the UK and abroad on AM on my vintage sets!

As for DAB - I use it here quite a lot as the stations I enjoy are not available via traditional radio. It is solid whereas reception on FM here can be difficult with much aerial waggling - I really need an outside aerial. I have a few kitchen type DAB receivers around the house as I got my first one nearly twenty years ago (a Pure woody - still going strong) and with ageing ears I'm probably not the most discerning listener though I do notice if sound quality is particularly bad. The DAB sets are convenient and the presets make them simple to use. I sometimes listen online but only if I'm near a computer. I do notice a quality improvement on the computer - not least because I then get stereo.

Anyway, I think that copy needs a rewrite. Not getting frequency confused with wavelength might be a start!

[Terry]

I've taken a screen grab for posterity and to add to my technical library.  

I hope that this is not indicative of the quality of the rest of the contents of your library!

Out of interest, I posted that link on the uk.tech.broadcast group. Some of the responses are fairly predictable although the thread seems to have wandered off in the general direction of RDS now ...:

"What an absolute load of bilge. The first two paragraphs - especially
the first - are both factually and technically WRONG!

How in heaven's name do they get away with it!"

"Hellfrauds?..."

"Amazing even for Halfords."

"This sounds like what occurs if you take a technical article and have it sub
edited by a member of the public who knows nothing about the subject."

[Refugee]

Perhaps they have employed someone from some far away place where they really do use tape recorder bias oscillators as radio transmitters.

[Mike Watterson]

Ha ha ha!

Curry's (who own the now obsolete named CPW) also started as bicycle sellers and have amusing in store descriptions. I think they'd have been better getting in bike sales than buying CPW, which seems to have less trade in phones than Tesco, and Tesco want to sell their phone service.