Radio 3 - FM reception

[Lateralthinking1]

Are you content with FM reception for Radio 3? Although living on the edge of Greater London at its second highest point - Surrey in all but official name - I find that it leaves a lot to be desired.

As the music battles with whistle and discordance, and not only when there is a piece by Birtwistle, I am in little doubt that there are one or two amateur DJs nearby. On the dial, that is. They may be just six miles away in Croydon but in all likelihood it's Kennington or Streatham.

I don't think it is those though. I just can't believe that anything ridiculously powerful could be emitted by them, even if they are broadcasting from a tower block. It seems to me that the boost behind 3 is less than that behind 4 and that this in turn is less than that for 1 and 2. So is it just my radio - in fact every one I have in the house - or is it a common problem?

[salymap]

I get quite good reception in Sidcup, apparently from the Crystal Palace transmitters. Any occasional boominess I put down to the position and cheapness of my little CD player/radio. DAB is worse though.

[rauschwerk]

You don't describe what kinds of radio and aerial you are using. What you describe as the 'boost', however, has little to do with the case with an FM system.

[BetweenTheStaves]

You can get birdies and whistles due to atmospheric conditions. Have you contacted BBC Engineering about this? I have always found them courteous and helpful.

[Lateralthinking1]

Thank you for these comments. I am about eight or nine miles from the Crystal Palace transmitter and much higher up but there are a number of significant hills in between.

I have two ordinary portable radio sets and a much bigger one, like a ghetto blaster, with two speakers. Two are kept at the back of the house; one is at the front. All have their aerials fully extended.

I don't get the same problems with DAB and Freeview. It is just FM.

[maestro267]

Not content at all. I can never get a consistently good FM signal here in Swansea. Could it be that the further west of London you are, the more R3 neglect you?

[Bryn]

I live over 40 miles north-west of the Wrotham transmitter at which my 5 element Yagi (mounted a couple of metres above the chimney of this two storey house) and get excellent reception most of the time. As implied by rauchwerk, the properties of your particular installation can make a big difference. I used to live in Finsbury Park, next door to the control office of a minicab firm. Nothing I did was able to prevent the breakthrough of their messages. In my current location, my next door neighbour (I live in a semi-detached house) operates as a private chiropodist. A drill/polisher she uses caused major interference to both analogue radio and television reception until I rewired the aerial system with high quality braid and foil screened cabling.

[Don Petter]

Thank you for these comments. I am about eight or nine miles from the Crystal Palace transmitter and much higher up but there are a number of significant hills in between.

Crystal Palace is only a repeater at 4kW. Depending where you are, you might do better with a directional aerial aimed at the main Wrotham transmitter (250kW)?

It gives an excellent signal down here in Sussex (Though there are some local bad spots, Eastbourne for one).

[Donnie Essen]

Well, I get a fine signal in Streatham, that is, I don't notice nothing wrong with it or interference from other stations. That's on my new Roberts Ecologic DAB (but I only use the FM signal on it). Tower blocks don't rise too high round here, really. Saying that, is there a difference in the FM signal between ones that have DAB capability and those that don't? My woman, she has an older style Roberts (with the little movable strip that goes along the frequencies when you move the dial) and can't get some stations without interference.

[Spatny]

The big secret with exceptional FM reception, is to have the aerial installed by someone who knows about FM, and not any old TV aerial installer. I spent loads of time (& money) on getting good FM reception. I now just use a single horizontal dipole correctly aligned to Wrotham. I don't suffer with any interference, even on high pressure weather days. its clear as a whistle.

[rank_and_file]

I agree with Spatny, and my Naim 001 gets a very clear signal with an exterior aerial pointing at Wrotham. I used to think that the signal came from Crystal Palace but I am told that, in essence, Crystal Palace is really only TV signals, plus a FM repeater.

[Don Petter]

My main aerial is indeed a proper FM one with attached reflector rods, albeit only laid on top of the loft insulation, with the right orientation for Wrotham, rather than fixed to the chimney. (It’s in a loft which has no other content, unlike that in the other half of the house!)

For the kitchen radio, however, I made up a simple dipole from two lengths of wire laid along the picture rail (remember those?) as the wall is near enough at right angles to the Wrotham direction. The length of wire is not terribly critical, but if my maths are right for R3 at 91.3 MHz, the theoretical figure for a quarter wave is 32.3 inches each. The inside ends of the two wires are joined to the inner and outer of a coax cable which feeds into the set.

Even this jury rig will give vastly better results than an internal aerial or a little chrome telescopic type.


Addendum

If your radio has a balanced aerial input available (shown by a pair of twin terminals rather than a coaxial socket), making the home-made dipole becomes even easier, as you can use just a length of twin flex with no joining.

Obtain a suitable length of side-by-side twin flex and for 32 inches at one end, separate the two insulated wires to form the arms of the dipole. The remainder of the flex is then the downlead to connect to the set. (In case this is not clear, you should end up with a ‘T’ shape, the two top arms are single wire, and each approximately 32 inches long, the stem of the ‘T’ is the twin wire down to the radio.)

If you don’t have my conveniently orientated picture rail, the thing can become a bit flimsy and unwieldy. One solution is to tape the horizontal wires along a length of wooden dowel or light batten. You can then hold it aloft to find a good position for reception by experiment. How you fix it in that position I leave to your ingenuity. It must be admitted that the end product is more suited to a study than the drawing room.

[Lateralthinking1]

Thank you to all for these helpful comments. I have found this link which seems useful.

http://www.bbc.co.uk/reception/

It has confirmed tonight that my transmitter is indeed Wrotham although that is much further from here than Crystal Palace. I haven't located the respective power of each in regard to FM but interestingly it is exactly the same in both instances for DAB.

I lost R3 completely tonight on FM from 9.22pm for the best part of an hour but the diagnostic tool states there are no problems at Wrotham. That was a very unusual occurrence but it remains the case that the overall reception could be much better.

[Don Petter]

I haven't located the respective power of each in regard to FM but interestingly it is exactly the same in both instances for DAB.


You should read my posts! :winkeye:

Quote from M8:

Crystal Palace is only a repeater at 4kW. Depending where you are, you might do better with a directional aerial aimed at the main Wrotham transmitter (250kW).

[Anna]

My R3 reception is dreadful. My transmitter is Wenvoe but we have a relay mast here. During the evening reception drops to near enough impossible to listen to, ditto R4. OK, I can listen via FreeSat or the computer, neither of which is convenient (i.e. I need to listen in the kitchen or bedroom and need a portable radio) But why is it, ClassicFM is clear as a bell?

As to DAB, forget it, I haven't invested in it but my neighbour has, and it's dreadful. Funnily enough R4 on LW is brilliant (I use an old Bush Echo bakelite for the cricket!)

[Lateralthinking1]

Interesting comments.

Don - My apologies. I did read it and with interest. Clearly the brain cells were having problems with reception at 11pm last night. This weekend, I intend to locate the direction of Wrotham and make some suitable adjustments - Lat.

[johnb]

I haven't located the respective power of each in regard to FM but interestingly it is exactly the same in both instances for DAB.

I believe you will find that Radio 3 FM is transmitted at the same power as R4, R2, etc.

The impression that it is broadcast at a lower power is probably due to the fact that R3 has a far, far greater dynamic range that the other channels which means that the average sound level on R3 is lower.

The other thing that comes out from various posts is that many people are using portables. It has always been the case that, to get the best reception from FM, you need to use a decent external aerial (not one of those circular things you sometimes see). If you live in a marginal area this is even more the case. Having said that, I can't see anyone bothering with an external aerial for a portable radio.

One of the problems with FM is that it can pick up pirate stations, etc but it might be possible to minimise the effect with a multi-element directional aerial.

[Don Petter]

Interesting comments.

Don - My apologies. I did read it and with interest. Clearly the brain cells were having problems with reception at 11pm last night. This weekend, I intend to locate the direction of Wrotham and make some suitable adjustments - Lat.

My post was tongue in cheek, as I hope you realised. Good luck with your adjustments.

[Ferretfancy]

johnb

Unless practice has changed dramatically since I left the BBC, the permitted dynamic range on all sources remains at 28dB, and the same goes for television sound. I'm still not convinced that the transmitted power is the same across the networks. Try using a good FM tuner at a time when Radios 3 & 4 are transmitting news bulletins at the same time and switching between them. The peak level on speech should be the same on both networks, but in my experience R3 sounds lower.
I'm assuming that neither channel is using Optimod at the time.

[Bryn]

Ff, I think things might just have moved on somewhat in the interim. Even in 2007 wider dynamic ranges were to be observed for both FM and DAB on radios 3 and 4. Take a look at some of the hystograms (and handy search term to find them within the document) here (http://www.audiomisc.co.uk/HFN/DABvsFM/likewithlike.html). Since then DAB has been further tweaked and though I don't have necessary aplication to measure dynamic range directly here, I have found a wider ratio between peak and RMS levels in Radio 3 DAB braodcast in the past couple of years, which is a fair reflection of a widening of dynamic range. With the new HD Sound facility on the iPlayer, the ratio is even wider.

[Gordon]

I think Bryn is quite right that things have moved on a bit in regard to dynamic range. I know that the Optimods and DR control in general are set differently for Radios 1, 2, 3 and 4, R3 being the least aggressive by far, despite what the complainers say.

FM networks were designed assuming external aerials [30 feet up, so on the roof] and it is only the improvement in front end design [low noise figures, better implementations etc] that portables without external aerials work as well as they do at the edges of service areas. Same goes for portable TVs. In-loft aerials can work well because dry slates or tiles absorb little at FM frequencies but may do so more when wet or covered in ice. The roof also adds to the aerial noise temperature which will be important only if you are really struggling for signal - in which case external on a pole is best. The main problem with in-loft, especially with large aerials for FM [easier with smaller TV aerials], is being able to align the aerial correctly [depends on roof timbers and how much stuff you have stored up there!!].

All the high power BBC stations at Wrotham except R1 [half the power of the others] put out the same RF power with the same aerial radiation pattern to get the same coverage. The polarisation is slant so half the power travels horizontally and half vertically so the orientation of your aerial might matter depending where you are. Polarisation can change in transit due to reflections for example. [NB: All DAB is vertical only, so an aerial in the kitchen made of twin flex on a curtain rail, like someone described above, is fine for FM but will need to be vertically arranged not horizontal for DAB and be a bit less than half the size]. The local relay at Xtal Palace is nominally a 60th of the power of Wrotham, actually 30th taking account of polarisation, so, other things being equal ie the radiated power in the direction of Lat's house due to the radiation patterns, is very much less. How much further is Wrotham away than Xtal Palace? If it is three times as far the signal will be nominally 9 times weaker but with the massive power advantage of Wrotham Lat must still be better off there. Lat says he is at a high point in which case he is very likely to have no high ground in the way. The 30 times power advantage is wiped out if he is more than square root of 30 [about 5.5] times further away [other things being equal].

I live about 55 miles north of Rowridge [Isle of Wight] which is a 250kW sant polarised site and I get a massive signal on an external horizontal 6 element Yagi aerial. My Quad 4 tuner attached to the HiFi shows signal strength at the top of its scale and I have no problems of overloading the receiver front end. Reception is very low noise with no interference at all - and low noise too, when there is no sound between items there is no audible hiss. Oxford is a similar distance to the North, in fact somewhat nearer, but has hills in the way and delivers a good signal but more variable hence my choice of Rowridge. Our kitchen portables use their own inefficient whip aerials and FM reception is poor but tolerable so we use DAB whose transmitter is only 7 miles away!!

I think that Lat's problem is probably two things together: Firstly not receiving from the right transmitter - check the frequency against the charts and you'll soon see if its Xtal Palace [R3 is 91.0MHz Vertical] or Wrotham [R3 is 91.3MHz Horizontal/Vertical] - and so having too little signal strength as well as using a portable receiver with an aerial which probably has little gain, if any. Secondly because the signal is weak and the receiver is struggling it is more susceptible to local interference from anywhere, piracy not ruled out in that area. Normally FM is good at rejectiing an unwanted signal but do give the receiver a chance by giving it the best input signal you can. Upstairs should be better than down. Retune to Wrotham and you'll most likely get more signal. Sometimes too much signal can also cause problems like birdies, especially on poorly designed receivers but I don't think think that this is Lat's problem.