BBC Radio 4 long wave reception problems etc.

[G8DLG]

Every now and again I find BBC radio 4 programs distorted,very spashy speech,(sibilants) DAB seems fine but VHF poor and LW really bad,I found studio and news bulletins very bad,but recorded material seems ok.As usual the BBC dont seem interested.Has anybody had this on LW?

[Skywave]

Hi!

I hear what you say that it only appears to be on certain types of programme material. Could this just be co-incidence? I wonder if your receiver / your location is being subjected to interference - like a really strong locally-generated electro-magnetic field - a nearby transmitter or something? Perhaps a listen on a different set, or using a portable set and trying different locations might throw some light on the issue.

As a Radio Amateur, I know that you'll understand my drift here & what I'm thinking of - so I needn't go into details.

Then again, could the set itself be faulty? (He says, leaving the blindingly obvious to the last!)

Although nowhere near your location, I regularly listen to Radio 4 on LW in my car - with an inefficient aerial - I don't get your reported problem.

Al / Skywave.

[GJR 11L]

I usually listen to the BBC R4 AM service on MW, but have just tried the 198KHz LW position tonight and it seems fine here.

[G8DLG]

Originally Posted by Skywave

Although nowhere near your location, I regularly listen to Radio 4 on LW in my car - with an inefficient aerial - I don't get your reported problem.

Its on all the sets I have,no matter what antenna I use or direction,the BBC say its due to their digital audio processing,and that I should listen on DAB,what rubbish! They,once told me that it was a poor earth at the Droitwch transmitter in the summer months when the ground was dry,but it was cured when the rain came!

[paulsherwin]

The problems on LW and FM are unlikely to have the same cause.

There was indeed a LW problem about a year ago which resulted in distortion on the Droitwich signal - this was a fault which took a surprisingly long time to sort out, though it's OK now.

Sibilance and roughness on FM is normally cause by multipath reception or co-channel interference, and is related to high pressure weather conditions. FM reception can be quite poor in parts of London because of the many large steel framed buildings.

R4 sounds coarse and gravelly on DAB all the time because of the very low bitrate, but I suppose people get used to that.

Paul

[Skywave]

A few further thoughts that might just help . . . .

In addition to Paul's comments above - which sound like a very likely set of explanations to me - have you tried listening to other stations on VHF and LW when the problem is evident? Is it unique to BBC transmissions? An if so, (on VHF), is it only R4? I'm still thinking about strong signal overload from some yet-to-be-identified RF source, even if it is affecting LW and VHF - "miles" apart in frequency.

I know that sounds pretty unlikely - given the freq. seperation - but after Paul's comments - I'm quite stuck for any other suggestions. Sometimes, strange problems have unusual (read: not obvious) causes.

As I said before, since you're a long-standing Radio Amateur (G8 plus 3), I don't feel that I need go into the technical detail on my thoughts.

Al / Skywave.

[Skywave]

Hi.
Lunchtime today - sitting in the car eating sandwiches - I listened to BBC R4 on LW - and remembered your OP.



By listening carefully to the nature of the transmission - as opposed to the information therein - I could just detect a slight tendency for the audio response to be a little over-emphasized on sibiliants. If this is what you are referring to, then my earlier suggestions are obviously incorrect

But this effect was not really "significant" (to my ears) - and I did not find it particularly annoying nor did it disturb my enjoyment of the programme.

Hope that this helps.

Al / Skywave

[G8DLG]

Hi,
Yes thats the distortion,depends on whether it comes from studio or recorded,try listening to news!It can be very annoying,they have admitted they have a problem with the audio processing,it is the same with R4 FM,although not as so pronounced,but DAB (bless it!) is very clear.
I do try to listen to Radio 4 quite a lot,theres not much else!

[Skywave]

Ok - so we seem to be getting somewhere with this!

In actual point of fact, in my earlier posting it was indeed the news on BBC R4 on LW that I was listening to!

I must say that for myself, I didn't find the quality of the transmission particularly annoying - but then again, I know that my hearing is pretty duff at the mid- to top-end of the audio spectrum. I need to have the treble control turned to max. for speech, music, W-H-Y to sound "right".

So I guess that's as far as we can go on this - no?

Al / Skywave.

[mickjjo]

I can get Radio 4 on no less than five different platforms so it is interesting to compare the sound quality of the different versions. F.M. ought to be the best here as Wrotham is only 10 miles away, but the audio is not good with bad sibilance on news broadcasts just as G8DLG has noted, Recorded programmes usually sound good. L.W. is a strong signal but always sounds a bit muffled without much top whereas the R4 Medium Wave outlet is a little brighter and clearer but nowhere near the quality attained by Arrow 675 or even Big L at its best
Radio 4 via DAB and Freezeview sound about the same and close to F.M. but with the slight but irritating grainy distortion due to the low bitrates.
I suppose for much of R4s output the quality doesn't really matter but with all that money they should be able to do better.

Regards, Mick.

[arjoll]

Without having *ever* listened to Radio 4, but reading all this, it does sound like they have issues with audio processing - either the wrong settings or maybe using the same processor for different platforms.

I know that Rhema struggled with similar issues especially for the Southern feed where they have a mix of large AM and small to medium FM stations, processing mostly at the head end to save costs.

Adding to this I'm not sure of the transmission characteristics of LW. If they are the same as MW then something standard like an Optimod 9200 or 9400 should sound great, otherwise they'd either have to manufacture something suitable (do the BBC still do engineering?) or modify/adjust something to 'fit'.

Also if it used to sound good but now doesn't (and sounds like they're pushing the highs at bit hard) then it may reflect a different path to the transmitter - they may have switched from a low bandwidth leased line or STL to a digital STL or satellite feed, for example. This could potentially let more highs through and the older processing just can't cope - something they just may not have thought of. Potentially easy to fix - say a parametric before the processor - but the problem would be getting past the receiptionist/call centre/help desk at the BBC to a tech who has some kind of clue.

In terms of the FM broadcast the sibilance could be multipath, an overdriven analogue STL (actually that could cause harshness on the LW feed as well) or overdeviation.

Broadcast processing can be really fiddly to get to sound 'good' on every radio, especially as you start pushing things a little to get some more 'loudness' - I've spent hours trying to get Life fm's Southland feed sounding good through the Aphex 2020, just to have someone in Auckland tweak the head end processing so I have to do it all again

[Skywave]

On VHF sound transmissions, if the pre-emphasis in the exciter is not set up just right, you can easily get too much "top end" in the audio range.

For reference:
In Region 1, 88 - 108 MHz (which includes the UK), the standard is 50 us; in Region II, 88 - 108 MHz (includes N. and S. America,) it is 75us. Not sure about Region III (76 - 90 MHz) - but I suspect it is 75us.

Al / Skywave.

[arjoll]

NZ uses 50uS (as does Australia) but not sure what region we're in!

Setting a processor to 75uS does sound terrible, and I'm sure that the BBC wouldn't do that (although there are all the comments here about standards slipping...). It produces a harsh, bright unpleasant sound. It is different to an overdriven STL or exciter - that would sound ok with quieter programme but 'spit' like crazy on some speech and music.

[Hybrid tellies]

Recently I have listened to a few programes on Radio 4 on 198Khz and found the audio quality to be of a very high standard.
Lets hope it continues.

[G8DLG]

Are you listening on LW,?since they still have not sorted this problem out,and from what it now appears,they dont intend to!
BBC radio 4 are well noted for this sibilant distortion,very bad on LW,and tolerable on VHF/FM,where it does not seem too noticicable.
DAB and internet sounds very good,well its got to be! they want to pull the plug on Droitwich, they just need this poor audio exuse to shut it all down.

[Skywave]

Well as it just so happens, today, Saturday 10th. February, at about 07.15 am, I was listening to BBC R4 on LW, and I must say that this "accenuated sibiliant problem" was very noticable! Quite objectionable, in fact.

Al / Skywave.

[SWB 18]

I agree R4 from DEI does sound poor at present and has done for a while now.

I suspect that the Tx's (not now owned by the Beeb of course) are behaving themselves and the audio processing applied by the Beeb is causing the problems.

Wonder why G8DLG thinks that the Beeb want to 'pull the plug' on DEI R4?
It has a far greater significance than just a medium for getting out 'The Archers'. What about the NPL frequency standard on 198Kc/s, tele-switching of 'Economy7' meters, the Shipping Forecast, World Service during the night, a means easily getting UK news when travelling in Europe, plus a few other roles too?

Trips out to standby, before wandering too far OT..........

Phil.

[Hybrid tellies]

Originally Posted by G8DLG

Are you listening on LW,?

You are right, I was listening on a radio which does not have much top. When
listening on my Bush TR130 the problem is all to plain.
All I can sssay is sssssory

[Steve_P]

What'll be happening, I speak from Bitter Experience of these large companies, and worse when 2 or 3 companies are involved, is that each company's engineers go 'Our gear's alright so it must be somewhere else'.

Radio 4 sounds bad on News Broadcasts in Particular, on LW and FM. This suggests to me at any rate that the Transmitters are OK. What I'd like to know, if anyone can help here, is how the programmes are fed from Studio to Various Forms of Transmission.

I know that R4 LW and R4 FM are separate, they have to be for the b***** cricket! And also that both feeds go to Satellite, as I can get both feeds on my Digibox.

So, the problem is probably at Broadcasting House, as not that many lines across the UK can have the same fault! I'd go to the Studio Output Racks and have a listen to both circuits there. A close listen. The fault may not be immediately noticeable there but further down the line it certainly is!

P.S. Castle Crown Comms or whatever you are called now, please fix up the Antenna at Droitwich properly at some point soon! Even if it means taking it off the air and going to reserve antennas for a while...

Cheers,

Steve P

[Ray Cooper]

Steve_P:

Radio 4 sounds bad on News Broadcasts in Particular, on LW and FM. This suggests to me at any rate that the Transmitters are OK. What I'd like to know, if anyone can help here, is how the programmes are fed from Studio to Various Forms of Transmission.

The R4 long-wave feed travels from London BH to Sutton Coldfield on a digital fibre-optic bearer circuit (NICAM 728). From there, it goes on BT landline (copper twisted, private wire) to Droitwich. Reserve feed is available on another private-wire, and if everything goes pear-shaped there's an off-air RBL feed from Sutton Coldfield VHF, though this is of course problematic 'cos of the variations in programme content.

P.S. Castle Crown Comms or whatever you are called now,...

Crown Castle International: but then they got bought out and became National Grid Wireless when I last looked - but I think there's been yet another takeover since, don't know what the latest outfit is called. Don't very much care by this point, either. All this chopping and changing can't be very good for maintaining continuity and standards (he remarked stiffly, as becomes an old-time BBC Transmission engineer...)

...please fix up the Antenna at Droitwich properly at some point soon! Even if it means taking it off the air and going to reserve antennas for a while...

And therein lies the problem... there isn't a reserve antenna for R4 LW. Doing large-scale maintenance on this array is an absolute nightmare as a result. You can't just sling up a temporary array - even the present permanent one is grossly inefficient because it's well under a quarter of a wavelength long at 198kHz. Even if you had a temporary aerial on site, you probably wouldn't be able to work on the permanent array because of the colossal amount of induction that would take place into it from the temporary array - as it is, it's unsafe to walk about in the field carrying an extended metal ladder.

Back in the 'nineties there was a scheme afoot for a temporary LW site at Daventry, to cover the six or so months that a decent overhaul on this mast was likely to take. Lack of cash, and privatisation, knocked that one on the head. In the absence of a reserve array, the only alternative is lengthy shutdowns, and do the job quickly, rather than nicely.

In any case, even the design of the array is very much a compromise. Due to the very low carrier frequency, the fractional bandwidth of the signal (ratio of modulation bandwidth to carrier frequency) is much higher than for any MW station, to the extent that the match of the aerial is quite different for the two sidebands... so matching it is difficult. In order to compensate for the sideband anomalies, the audio input to the TX has to go through a phase-correction filter which does not leave the amplitude response unscathed. Additionally, and just to add to the agony, you can't actually do a direct performance test on the TXs because the signal coming out of the TX bears not much resemblance to what is actually being radiated - you have to test it via another correcting filter, which simulates the aerial. The only way to test it properly is to take a test receiver into the far-field region of the aerial - at least 5 kilometres away...

And then, there's yet another stumbling block - the sound input signal has to go via a digital bucket-brigade delay line to enable the precise timing of the modulation to be corrected. This is to equalise delays between Droitwich and the other users of 198kHz (Westerglen, Burghead) so that distortion in the mush areas where their signals overlap may be minimised.


G8DLG:

They,once told me that it was a poor earth at the Droitwch transmitter in the summer months when the ground was dry,but it was cured when the rain came!

In fact there's a fairly efficient earth mat buried in the ground to overcome variations in ground conductivity. There's so much current flowing in this mat that the ground doesn't stay wet for long - after a rain shower, you can often see the ground steaming.

Believe me, it isn't all beer and skittles at DEI. I often wonder that it sounds as good as it does... But then, if you're troubled by minor shortcomings of this nature, then you shouldn't be listening to LW/MW. It has never been sold as a quality service.