A Frequency Problem-HELP NEEDED!

[Charley B]

Hi
Can anyone enlighten me on this one:
My scanner over the last 3 weeks has had a lot of horrid buzzing background noise on 135.32, 135.05 and 126.07 the freqs Ialways listen to .The planes side is fine, only yours is noisy!I understand that the aerial for thesefreqs is on the I O Wight-has it gone from there or is there some other reason?
My scanner is elderly but is a good make and has never had this problem before! Would the TV man putting our digital aerial on the chimney have made any difference-(this is where my dipole aerial is)
Thanks
Charley B

[vintage ATCO]

Probably the Radiocommunications Agency . . . . . ;) :p

[Charley B]

Vintage ATCO
Very good!!!!!!!!!!

[Fox3snapshot]

Charley B are you related to the dude who is collecting old flight progress strip holders????

:E

[Charley B]

Absolutely not!Always been interested in ATC and like planes so it kinda goes together.When I see a plane going overhead its just nice to know what it is and where its going.
All the controllers that I listen to work DAMN HARDand do a great job something I would have loved to have done a few years ago!

[Numpo-Nigit]

Hi Charley B

Each of the London Control frequencies is transmitted simultaneously from two, three or even four widely-dispersed sites. With the recent prolonged spell of fine weather due to areas of high pressure over the UK, I suspect that you may be hearing two transmitters instead of the one you normally hear. That MAY account for the stange noises. If so, as soon as we get more typical weather patterns things should be back to normal. So, don't make any drastic changes to your set-up just yet!!

NN

[redsnail]

I think it's Manchester 133.8 has some terrible interference on it.

[HEATHROW DIRECTOR]

I think the positioning of the new TV aerial adjacent to your receiving aerial could be highly significant as TVs dish out a large amount of RF "noise". As a radio amateur I know a bit about this - but it's usually the other way round with my transmissions wiping out all the local TVs! Does the situation change when you switch the TV off at the mains? If so, I suggest you move one or other of the aerials. Has someone local you you recently installed a burglar alarm? Have you or any neighbour recently acquired a new PC.. or have you moved a PC nearer to your scanner? You're not by chance using a "booster" amplifier are you?

Scanners generally are not top-grade communications receivers and are "open" to noise which may have nothing to do with the frequency you are listening to. I have a fairly good wide-band receiver but it gets clobbered by various local interference.

Email me direct if you think I can help further..

[Capt H Peacock]

Because of the wide coverage required from a single frequency, many sectors are broadcast from two or more sites. If both transmitters were on the same frequency, they would interfere with each other (in the literal sense) causing all kinds of problems eg blank spots and a heterodyne whistle at the receiver.

To avoid this phenomenon, one of the transmitters is 'offset' by a certain amount, for instance London Volmet Main (135.375) as broadcast from the Greenford transmitter radiates on 135.385. This still produces a heterodyne tone (135.385-135.375=10kHz) but this is way outside the receivers audio passband. The listener doesn't therefore hear the heterodyne. Sometimes, at long ranges, the whistle is slightly perceptible in the background.

If you want to listen to both sides of the conversation, you'll need to select a broadband AM (10kHz or more) mode on your receiver so that both transmissions fall within the passband of your receivers front end.

Incidentally this method is only used in the UK to my knowledge. Over the water they 'bandbox' if they're only using one controller for large sectors.;)

[Charley B]

Thanks to everone who has tried to help with this little problem.
Tv was duly turned off at the mains just now and lo and behold the noise stopped!
TV man is to be summoned to take the digital aerial off the chimney and back to the back of the garage where it was before!!

[EGCC Rwy 24]

Well, while we are on a roll, how about this one:

Decent scanner, roof mounted aerial, not near any others. All Manchester frequencies absolutely fine, except 121.35 which has horribly buzzing noises.

Wife's portable scanner exhibits exactly the same problem - which eliminates the roof aerial.

Ideas all welcome.

Nick
Nick Locke's Reporting Points (http://nicklocke.co.uk/Points)

[Bigears]

EGCC Rwy 24,
Receive anything on or around 110.65?

[Simtech]

EGCC Rwy 24,

Is the buzzing continuous or does it come in bursts?

[EGCC Rwy 24]

Bigears - nothing audible on or about 110.65.

Simtech - it comes in bursts. From every few seconds to every couple of minutes and, generally, lasts for about five or ten seconds each time. The noise is best described as a cross between white-noise and a rasping sound.

Continued clues welcome!

Nick

[Simtech]

Nick,

Sounds like you might be suffering from breakthrough from a pager system. These things are the bane of many radio enthusiast's lives. My amateur radio equipment is sometimes affected but wideband receivers like your scanners are more susceptible. You can buy filters that connect between the aerial and the radio which claim to eliminate this interference (try looking at the adverts in Practical Wireless or Shortwave Magazine).

Regards,

Simtech

[Charley B]

Hello Im back again!!
On Fri the TV man arrived and returned the dish to the original place!Last night went to listen to 135.32 and the wretched buzzing noise was back!!!!!!!!Turned TV off at the wall then SILENCE (apart from ATC! )It does seem that most of this problem is either the new TV(32"widescreen run of the mill Tv) or the Damn digibox that he swapped over with ours when we called him out in the first place as the Sky was not working!!!!!
The digibox which we paid him £80.00 is Amstrad Crap and is So slow at changing channels ,if this is causing the problem it too may have to go------------this is all getting a bit expensive!!!!!!
Well done to the young guy on 135.32 last night between 22.00 and 24.00 you just didnt stop and sounded if you were really enjoying yourself!!

[Bigears]

EGCC Rwy 24,
Sorry, didn't realise that it was in bursts until Simtech asked.
Agree with his thoughts- heres a link which may help- never had to use one though- Notch Filter (http://www.ssejim.co.uk/page0007.html)

[Simtech]

Charley,

Most modern domestic electronic equipment (TV, computers etc) use switch-mode power supplies. These contain an oscillator which is effectively a radio transmitter. The emissions from these devices must comply (in Europe anyway) with the relevant CE regulation which specifies the maximum level of such emissions. A sample of each item has to be tested in an accredited laboratory to ensure that it complies; only then can it be sold. Unfortunately the CE regs are not very tight and many radio enthusiasts suffer the consequences. There are also cases where electrical goods (often imports from the Far East) are CE marked but have not been tested and approved.

A switch-mode supply can be designed so as not to cause interference but this costs money. Also, modern design practice dictates that the power supply is active whenever the equipment is connected to the mains, irrespective of whether it is switched on or not. I think they call it progress!



:mad: