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Old 22nd Aug 2017, 8:50 am   #81
Hybrid tellies
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Default Re: Radio 4 198 sibilance

Just a heads up. David Allett emailed me yesterday to confirm the fault on the Droitwich R4 198Khz transmitter had been cleared on Saturday, 19/08/17, afternoon.
I think its now sounding as good as it ever has.
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Old 22nd Aug 2017, 11:10 am   #82
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Default Re: Radio 4 198 sibilance

Excellent! Thank you Simon.
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Old 22nd Aug 2017, 12:02 pm   #83
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Default Re: Radio 4 198 sibilance

Seeing all of the posts concerning quality issues for R4 LW reminded me of my early years on the early shift (0615-1415) in the welsh region in 1970.
First thing through the door was to check the meters on the power cabinet, then the rack of ppms (peak programme meters on the master monitoring panel as well as the automatic monitors major for alarms. Then visit the small refreshment area and power the kettle! You need to prioritise!
Next, if there were no alarms going off, you sat down and went through all of the off air receivers for your area and monitored for quality. Incidentally R4 LW, from Droitwich, was one of the reserve feeds for R4 and always assessed for Quality. Even the pipsqueak relay on MW at Penmon was monitored for quality in North wales by the staff in Bangor.
I suspect that that none of that happens any longer. Members of this forum know how difficult it is to contact any body about quality issues in the BBC which appears to have gone from the British Broadcasting Corporation to the British Broadcorping Cast off Company or even the Broken Biscuit Company.
I remember the organisation shedding jobs and virtually all of the engineering department, this after transmitters had been sold off complete with as many staff as wanted to stay. They are now back to nearly as many staff as in my day but most are 'ARTISTS' and with some really gifted ones as recently noted after enforced declarations.

The Long wave service from Droitwich, still regarded in certain parts of the northern hemisphere as something worth listening to, is part of the professional output of the national broadcaster of this country! R4 was placed on this channel to provide both internal and external to this country, access to this information service!
If this was Germany and I am well aware that it is not, a different set of rules would ensue.
A decision would be made by the broadcaster service on an end of service date. this would be placed before the relevant leaders of the state who would consult within the population and either agree to withdraw the service or refuse and extend the life of that service.
Of course here in Britain we are better and know more, so we do the corporate thing and bring in 'Exsperts' ( sorry about the spelling). Two syllables Ex meaning, has been, and sperts, equals drips under pressure!
The decision is therefore to let it carry on and do nothing, then when it goes wrong, let it fester for a while and when the complaints rise to boiling point eventually get one of the contractors to sort it out. Of course most of you should know now that the BBC has turned into something that a previous Director General said would NEVER happen. John, now Sir John Birt stated in a staff publication, that the 'BBC would never become a Publisher Broadcaster. In selling off its' transmission chain and not being able to control the output it has become exactly that!
So R4 Droitwich is, as has been referred to, part of a legacy system.
I cannot think of any piece of equipment save satellite that covers most of the United Kingdom and from Iceland to Morocco and with such a pleasing mixture of programming. Yes the internet is fed with all of the different flavours of the BBC. I wonder how much all that costs to send across the world, bearing in mind, that we as licence payers, pick up the bill!
After that diatribe I must admit that R4 LW from Droitwich does sound very nice out in the middle of the country near Welshpool on my large floor standing RGD console set and my Murphy corner panel fed with 150 feet of aerial. No background noise, no mains born interference and you can hear the announcer draw in a breath and sometimes operate a fader on the console. In a darkened room it is still an experience!
Mike
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Old 22nd Aug 2017, 2:18 pm   #84
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Default Re: Radio 4 198 sibilance

Ah, the BBC that was...

This problem sounds like some software-based processor which needs the occasional reboot. Should be simple enough to give it a hit in passing every so often...
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Old 22nd Aug 2017, 3:32 pm   #85
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Default Re: Radio 4 198 sibilance

I have to say that until R4 first went faulty as "just a member of the public" I assumed that the situation outlined by Mike still existed. I thought that the possibility of BBC radio transmissions being anything other than perfect was highly unlikely. A bit like the British armed forces I just assumed that the BBC was the best.

I remember as a young teenager writing to the Engineering Department with what in retrospect were elementary enquiries and I always got courteous and informative replies. Another illusion shattered!!
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Old 22nd Aug 2017, 4:14 pm   #86
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Default Re: Radio 4 198 sibilance

Even the major transmitter sites are lights out operations nowadays, and there has been no routine off air monitoring for at least a decade. The transmitters all send telemetry to Arqiva but nobody is actually listening to the output.

As I understand it, the R4 LW distribution chain is separate from the standard BBC setup and contains lots of arcane redundancy arrangements dating back to its key role in cold war planning. All of this will be 70s and 80s custom built hardware and I have no doubt that there's nobody around today who understands how it all works. The sensible approach would be to decommission it and use a simple link to BH in London, maybe using a satellite or internet feed, but that would count as new capital expenditure and the BBC won't fund it. As a result we soldier on in an increasingly rickety manner.
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Old 22nd Aug 2017, 6:21 pm   #87
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Default Re: Radio 4 198 sibilance

Quote:
Originally Posted by Hybrid tellies View Post
Just a heads up. David Allett emailed me yesterday to confirm the fault on the Droitwich R4 198Khz transmitter had been cleared on Saturday, 19/08/17, afternoon.
I think its now sounding as good as it ever has.
Great news indeed, glad you got a response as he didn't bother replying to my last two emails! Perhaps he was receiving too many to get back to!
Enjoying nice Radio 4 sound again on my Murphys.
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Old 23rd Aug 2017, 4:27 pm   #88
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Default Re: Radio 4 198 sibilance

Quote:
Originally Posted by ndg-2000 View Post
Quote:
Originally Posted by Heatercathodeshort View Post
At 69 I am far too young to get involved with Radio 4
Haha brilliant, I'm 42 and Radio 4 is what's on in my van every day. Unless The Archers is on! Must be old before my time LOL.
I used to listen to Radio 4 when it was still on MW with my first home made Practical Wireless OC44 receiver. I used to fall asleep listening to Book at Bedtime and mother would come in and gently remove the earphone from my ear. I even listened to The Archers! I was still at school. Don't know what that says about me. (Or perhaps I do...)

Re R4 LW in the car: LW reception in my recent cars has been very poor. My current car (16 years old) has an upgraded radio (CD player!) compared with the one (cassette player!) in my previous car of the same model but older. Test Match Special was tolerable quality in the previous car and I could hear RTE reasonably out of town but LW reception is hopeless in the current one. (Bear in mind that Droitwich is just down the road from me.) MW was ok but it seems they were paying little attention to LW back at the turn of the century. In new cars it's probably all FM/DAB and bluetooth whatever.

The previous generation of AM/FM car radios seem set up for FM and to get acceptable reception on AM but not optimised for LW. The little stubby car aerials that are inevitably a compromise won't help.

In any hire or courtesy car I find that the presets are invariably set to various pop stations and Radio 2. A week ago, as a favour, I picked up a customer of a business where I go and do a bit and he immediately remarked that I was listening to "a decent station" - Radio 3.
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Old 24th Aug 2017, 8:58 am   #89
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Default Re: Radio 4 198 sibilance

Quote:
Originally Posted by gramofiend View Post
After that diatribe I must admit that R4 LW from Droitwich does sound very nice out in the middle of the country near Welshpool on my large floor standing RGD console set and my Murphy corner panel fed with 150 feet of aerial. No background noise, no mains born interference and you can hear the announcer draw in a breath and sometimes operate a fader on the console. In a darkened room it is still an experience!
Mike
I can relate to this, I live near Watford and now experiencing very good sound indeed. I'm constantly surprised at how detailed and pleasant LW can be to listen to on old radios. I'm wondering if the nature of the sound is more suited to vintage equipment than modern.
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Old 24th Aug 2017, 6:14 pm   #90
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Default Re: Radio 4 198 sibilance

Quote:
Originally Posted by Junk Box Nick View Post
Re R4 LW in the car: LW reception in my recent cars has been very poor. My current car (16 years old) has an upgraded radio (CD player!) compared with the one (cassette player!) in my previous car of the same model but older. Test Match Special was tolerable quality in the previous car and I could hear RTE reasonably out of town but LW reception is hopeless in the current one. (Bear in mind that Droitwich is just down the road from me.) MW was ok but it seems they were paying little attention to LW back at the turn of the century. In new cars it's probably all FM/DAB and bluetooth whatever.

The previous generation of AM/FM car radios seem set up for FM and to get acceptable reception on AM but not optimised for LW. The little stubby car aerials that are inevitably a compromise won't help.
When you upgraded the radio you *did* remember to wire up the +12V feed from the radio to the antenna-amplifier I hope?

I've sorted-out several people's expensive replacement head-units that had "hopeless radio reception" because the original head-unit had DC passthrough on the antenna-coax or a switched 'antenna' feed, but their new head-unit had no DC-passthrough or they'd assumed the "Antenna" switched-feed was for a motorised up/down antenna and hadn't bothered to connect it because their car didn't have such an antenna.
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Old 24th Aug 2017, 7:04 pm   #91
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Default Re: Radio 4 198 sibilance

The car came with the upgraded installation. From what I can see from the wodge of paperwork it was fitted from new.

I've thought of upgrading to DAB - that would double the value of the car
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Old 24th Aug 2017, 7:20 pm   #92
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Default Re: Radio 4 198 sibilance

Ah, I thought you'd done the head-unit upgrade yourself.

Modern car-antennas with amplifiers work badly on FM when not powered-up (pickup on the coax?) but pretty much not-at-all on LW under the same conditions!

I've just tried tuning to R4LW on my kitchen-radio PCR and the sibilance is definitely gone, though the PCR has its IF stages aligned for maximum-selectivity so the high-frequency components of the received signal get pretty effectively deleted anyway. I only noticed the sibilance in the past when the receiver was slightly off-tune.
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Old 24th Aug 2017, 10:25 pm   #93
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Default Re: Radio 4 198 sibilance

If this isn't a stupid question, what does the actual distortion that makes "s" sounds hiss look like?
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Old 24th Aug 2017, 11:23 pm   #94
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Default Re: Radio 4 198 sibilance

Clipping, although the effects can be quite complex.

You can get similar effects with low bitrate digital encoding, where the sibilant peaks can't be encoded properly.

None of us really knows what causes the R4 sibilance when it happens.
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Old 25th Aug 2017, 10:58 am   #95
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Default Re: Radio 4 198 sibilance

Could it be that the HF boost given to the audio (to cope with the narrow antenna bandwidth) somehow gets turned up?
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Old 25th Aug 2017, 3:12 pm   #96
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Default Re: Radio 4 198 sibilance

Although the BBC once used their long wave transmitters for Transmitting the Light Programme which became Radio 2 with a high percentage of music, using a carrier of 200 KHz (198 KHz now)
audio fidelity presents a problem especially when one considers the maximum audio frequency transmitted, to maintain 9KHz channel spacing, is 4.5 KHz.

From a conversation with a engineer, as an example, a modulation bandwidth of 20KHz is 10% of the carrier at 200KHz, and hence the Q value of the circuit is large such that modulation frequencies decrease quickly so limiting the higher frequencies which are necessary to give clarity of speech and some musical fidelity.

To compound the issue, the IF passband on domestic AM radios is often no more than 4.5KHz; that is GPO telephone sound.

Whilst I cannot find technical papers from the BBC on audio processing for their Long Wave service, listening to the station, it sounds as if the broadcaster is trying to get a quart out of a pint pot by modulating the carrier to its legal limit and audio fatigue soon sets in. Switching my receiver to a wide IF bandwidth gives some idea to the processing, which is similar to the BBC 720 KHz Radio 4 fill in transmitter used in London (for MP’s to listen to?), which is to my ears also still “hard work” when listening to the station..

It doesn’t have to be so. Tune to RTE on 252 KHz and it is a different world with a good AM sound quality without listening fatigue. Apparently, their Long Wave transmitter is for the benefit of the older population who no doubt can remember what a human voice sounds like!! Luckily it would seem that a listeners request for RTE to copy the BBC audio processing fell on deaf ears. No pun intended!!

Once upon a time the BBC, I know, here we go again, but seriously, BBC Engineering would compare off air and transmitted audio quality through Quad AM tuners but then many radios were available with variable IF selectivity and listeners complained about the sound quality if not right.

For the record, at higher transmitted carriers, say 1500 KHz a modulation bandwidth of 20KHz is 1.3% of the carrier and hence the Q value of the circuit is small allowing modulation frequencies to decrease more slowly increasing the readily attainable bandwidth. This also the reason why shortwave transmitters can sound much better than LW and MW ones do.

Hope this all helps.

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Old 25th Aug 2017, 3:49 pm   #97
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Default Re: Radio 4 198 sibilance

The RTE service does sound very good, but to be fair it is a very new installation - a new Transradio (Telefunken) transmitter was only installed in 2007. Maybe Arqiva would like to buy it if RTE stop using it
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Old 26th Aug 2017, 12:26 am   #98
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Default Re: Radio 4 198 sibilance

Re the Droitwich LF transmitter bandwidth, BBC Engineering #89 of 1972 January included a longish article entitled: “Reduction of Interference by Reduction of Modulation Bandwidth”, page 23ff.

Therein it was noted that the Droitwich transmitter was 1 dB down at 5 kHz. I have attached the pertinent pages from the article:

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Also, here is a frequency response chart from a 1935 paper on the Droitwich station. This could well have changed over time with transmitter and/or aerial upgrades and replacements.

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The restriction in bandwidth due to aerial Q was not immutable, though. The late Allouis LF transmitter was designed to have a ±10 kHz bandwidth – then the CCIR number for AM broadcasting - as delineated in this Wireless World item:

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The above-mentioned BBC Engineering article also mentioned compression as well as bandwidth restriction.

A subsequent brief item in BBC Engineering #97 of 1974, page 27 described the FL4/55 low-pass audio filter intended for use in the programme feed to MF transmitters. This provided a steep cutoff above 5 kHz, with a 3 dB lift at 5 kHz.

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The BBC EID sheet for the FL4/55 was dated 1973 June, so I’d assume that this is about when it was introduced into service. Prior to the use of this filter, MF broadcast bandwidths were essentially limited by the GPO landlines, typically 10 kHz and lower, although the lines to Brookmans Park had been at 15 kHz since the 1940s. I think that at some later time, the MF bandwidth cutoff was moved out to 6 kHz, but I don’t have a solid reference for this.

The editorial in BBC Engineering #97 was “A New Plan for L.F./M.F. Broadcasting”. Mentioned in it were bandwidth restriction, audio processing, and a common channelling plan for ITU Regions 1 and 3, with 8 kHz suggested! At the time, Region 3 used 10 kHz channelling.

Thus, we could mark 1973-74 as the “turnover” point, after which bandwidth restriction and compression became the norm.


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Old 26th Aug 2017, 12:52 am   #99
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Default Re: Radio 4 198 sibilance

Most of the present arrangements are likely to date from the 1980s, when the original 1934 transmitter was replaced and the distribution circuits re-engineered.

198kHz really was an important part of UK civil defence planning then - it was not expected to survive an all out nuclear war, but was to be the main channel of central government communication in any national emergency less serious than that, such as a limited nuclear strike, a civil insurrection or a complete failure of the national electricity supply. It was also used as an indicator of national survival to UK ballistic subs on patrol (though it's a myth that sub commanders would launch a nuclear strike solely on the basis of the transmitter going off air).

Because of this, the programme distribution arrangements are different to those of the standard BBC transmitter networks. They were (and possibly still are) classified, and are likely to involve lots of 1980s defence comms technology. I believe this is the reason why faults are difficult to fix and keep recurring.
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Old 13th Sep 2017, 12:37 pm   #100
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Default Re: Radio 4 198 sibilance

Here we go again! just when I thought it might have been sorted out for good the poor sound is back on Radio 4 again.
This really does spoil the listening pleasure when you know Radio 4 can sound very good when the transmission is working properly.
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