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simone
26-11-2005, 16:46
Hi all,
here is an example of one of the BBC WS analogue MF transmissions using AMSS to broadcast some data, besides the station label there is also information for receivers (like AF lists) referring to the DRM broadcasts.
Simone
PS: Thanks to the BBC for making the sources available!

simone
26-11-2005, 16:57
and here the same data received on HF
Simone

dk8cb
26-11-2005, 19:19
And here is a screenshot of the improved version with a bigger AFS (alternative frequency service) window that now allows one to see everything without one having to use the slider.

Very nice!

Roland

carknue
27-11-2005, 09:59
Who else uses AMSS? Just BBC?

simone
27-11-2005, 10:44
Hi Carsten,
as far as I know, at the moment only BBC WS are using AMSS on their AM transmissions on 648 kHz and 9410 kHz (see AF´s in the attachments above), hopefully there will be some others in the future!
Simone

dk8cb
27-11-2005, 14:25
For an explanation on what AMSS is all about and how it works, have a look at this explanation (http://drm.sourceforge.net/forums/index.php?showtopic=59&st=0&#entry293) given by James Briggs.

Roland

jbriggs
27-11-2005, 16:31
Try Beidweiler (234 kHz) !?

carknue
27-11-2005, 16:42
Originally posted by jbriggs
Try Beidweiler (234 kHz) !?

Yeah, here it is.

dk8cb
27-11-2005, 16:52
Originally posted by jbriggs
Try Beidweiler (234 kHz) !?

Vraiment !

A bit different on the new AMSS window in today's CVS release, see screenshot.

Roland

simone
27-11-2005, 18:50
Hi all,
strong signal from Beidweiler (thanks James for the frequency information), no problem decoding the AMSS, but that´s what it looked like after tuning in again on a BBC frequency ;)
Btw is there a problem with signalling or are all the stations really not using any type of carrier control?
Simone

jbriggs
27-11-2005, 21:17
Btw is there a problem with signalling or are all the stations really not using any type of carrier control?

I think that 648 kHz does use carrier control, either AMC or DAM. I think 9410 kHz does not use carrier control, but I am not totally sure. I can check.

Just a bit of info for those not familiar with Dynamic Carrier Control (DCC) & also the reason this is signalled:
With a normal AM transmission the power in the central carrier is always fixed. There are different types of DCC, but essentially they allow for lowering the power in the carrier at certain times. This lowers the overall power consumption at the transmitter. However this could cause confusion for a receiver trying to demodulate the phase information from the main carrier because it will be varying in amplitude too due to the DCC. Therefore the type of Carrier control is signalled and the receiver can better decode the phase information if it can predict the amplitude variations due to carrier control.

jbriggs
27-11-2005, 21:28
I am moving this thread to general topics as I think it is of wider interest.

DRM-Fan
27-11-2005, 22:30
Originally posted by dk8cb


Vraiment !

A bit different on the new AMSS window in today's CVS release, see screenshot.

Roland

What new CVS release ? You mean Dream ? Is this 'available' ?

DRM-Fan
27-11-2005, 22:32
So RDS for AM then. Did'nt Germany want to use this (or similar) technology back in 1990 but could'nt for some reason ? One reason I think why Ofcom (name not this then) backed down from using c-quam for am stereo in the UK...

dk8cb
27-11-2005, 23:11
Originally posted by DRM-Fan
What new CVS release ? You mean Dream ? Is this 'available' ?

Dream's latest source code release is always available via the CVS (concurrent version system) and can be downloaded ('checked out' in CVS language) from cvs.sourceforge.net using a CVS-client of your choice. Of course you have to compile the executable from it.

Roland

DRM-Fan
27-11-2005, 23:17
Thanks Roland though now have a complited version downloaded from a certain website I had partially forgoton about 1.5 CVS.

THe AMSS decoding is amazing as I'm barely getting BBC WS on 648 but the AMSS data shows 100%! I hope more station adopt this system

dk8cb
27-11-2005, 23:19
Originally posted by jbriggs
... However this could cause confusion for a receiver trying to demodulate the phase information from the main carrier because it will be varying in amplitude too due to the DCC.

Since the information is entirely in the phase of the signal, if I understand it correctly, wouldn't it be sufficient if the receiver just limits the received signal at a sufficiently low level as any FM receiver does? You can easily achieve 60 dB of AM suppression this way. Shouldn't this be sufficient to get rid of any amplitude variations generated by carrier control and/or fading?

Roland

dk8cb
27-11-2005, 23:41
Originally posted by DRM-Fan
So RDS for AM then.

You could term it that way. Similar systems have been used for a long time to transmit data along normal programmes. To my knowledge, Droitwich, now transmitting on 198 kHz, formerly on 200 kHz, carries a phase modulated time signal using a similar system. Radio-controlled clocks make use of such phase modulated transmissions from longwave transmitters (MSF, DCF77) to obtain accurate date and time information.

Roland

jbriggs
28-11-2005, 15:21
sufficient if the receiver just limits the received signal at a sufficiently low level as any FM receiver does?

Roland this sounds like a valid approach, maybe the receiver manufacturers won't need to use this extra information. But the approach to take is up to the receiver designer.

Andreas
28-11-2005, 16:39
As reception of 234 kHz is impracticable at my QTH due to an yet unidentified source of hum I tried 648 kHz instead.

Yes it works!

Edit: But it takes some time on 9410 kHz. AMSS acqusition requires exact tuning by hand to the centre of the carrier. However data are lost repeatedly....

:mad:

Andreas
28-11-2005, 17:19
I must correct myself:

Although I would rate received audio with O= 1 AMSS works also on 234 kHz from Luxemburg. It's amazing!

But still no success with 941o kHz although audio there is - let me say O=4 to 5. Mhmmmmm ????

dk8cb
28-11-2005, 20:19
Originally posted by Andreas
... But still no success with 941o kHz although audio there is - let me say O=4 to 5. Mhmmmmm ????

I had the same effect yesterday. When I tried in the early evening, it worked perfectly on 9410 kHz despite a weak signal. When I tried again later, this time with a strong signal, it didn't work. I guess, different transmitters at different sites are used at different times of the day, one using AMSS and the other not using it.

It works very well at the moment (2115 UTC) and there is no need to position the cursor precisely, I always let Dream do it by itself, see settings in my screenshot (Auto frequency acquisition and PLL).

Roland

radiomann
28-11-2005, 20:47
Maybe a silly question but how come I have no AMSS on Dream?

Paul

dk8cb
28-11-2005, 21:05
Originally posted by radiomann
Maybe a silly question but how come I have no AMSS on Dream?


What is your version? AMSS has only been implemented last saturday on version 1.5, you won't find it on older versions.

Roland

radiomann
28-11-2005, 21:07
Originally posted by dk8cb


What is your version? AMSS has only been implemented last saturday on version 1.5, you won't find it on older versions.

Roland

Hi Roland,
I downloaded version 1.5 today all I see is a DRM button?

Paul

dk8cb
28-11-2005, 21:52
Originally posted by radiomann
I downloaded version 1.5 today all I see is a DRM button?


Now I see clearer, you mean you downloaded an executable today and you now miss the AMSS button in your version. Well, the screenshot is taken from an even newer cvs version which I compiled yesterday. On your version, AMSS can be activated via the settings menue, if I remember it correctly.

Roland

simone
28-11-2005, 22:04
Hi Paul,
just click on settings and choose AM and the AMSS window will be opened.
Simone

dk8cb
28-11-2005, 22:14
Originally posted by simone
Hi Paul,
just click on settings and choose AM and the AMSS window will be opened.
Simone

Now I remember that on my first try with the previous version, I also did not see the AMSS window because it was located behind the AM window. Just move the AM window a little to the side and you will see ...

Roland

DRM-Fan
28-11-2005, 23:15
So can we expect to see AMSS implemented next year as DRM radios become available which have this 'built in' to the spec like the Roberts RD20 ? I'm thinking of course also an excellent tool for MW dx'ing but I guess it will never become common place...or will it ?!

radiomann
29-11-2005, 15:43
Thanks Roland & Simone, it was hidden behind the other window.

Paul.

simone
29-11-2005, 18:15
Originally posted by dk8cb
I guess, different transmitters at different sites are used at different times of the day, one using AMSS and the other not using it.

From what I have noticed so far, I think it is only one site using AMSS on 9410 kHz and that´s Limassol/ Cyprus, the schedule should be :
0000- 0200, 0500- 0600, 1700- 2200 daily
0900- 1000 Sundays
Maybe James or someone from the BBC would know better(?)
Simone

jbriggs
29-11-2005, 20:46
Yes Simone, The AMSS modulator is fitted to 1 of the BBC's Cyprus transmitters, so any 9410 kHz originating from any other BBC or VTC site or even any of the other 9 HF transmitters at Cyprus won't have AMSS modulation.

simone
30-11-2005, 04:11
Hi James, all,
unlike mentioned in my post above there is no AMSS on 9410 kHz at 0500- 0600, so it is either not from Cyprus as scheduled or another transmitter is being used.
Simone

mitajohn
30-11-2005, 16:01
Hi all,

I have just received the AMSS on 9410, look at the attached file.

John

Johnbs
30-11-2005, 22:05
I've just read this thread, thanks to an alert from James.

1. 648 does use carrier control: what the BBC calls DCC. So it should be signalled as such (needs correcting).

2. The reason for "telling" the receiver about the carrier control being used by the Tx is to allow future "digital" receivers to more perfectly undue the carrier control. The original DCC time-contants were chosen to be approximate (reciprocal) matches to the typical AGC time-contants found in AM receivers. Hence the Rx AGC effectively removes the varying carrier amplitude, just as it does when dealing with varying propagation loss. The system thus created is rather like a simple compander.

If future Rx designers are given the precise details of the Tx AMC time-constants and laws etc, it should be possible to obtain an even more precise match in the receiver, hence a (theoretical) overall improvement in fidility. It may in practice be a bit of silk "purse from sows ear..."


John

simone
20-12-2005, 16:29
Originally posted by Johnbs
1. 648 does use carrier control: what the BBC calls DCC. So it should be signalled as such (needs correcting).
John
Hello John,
as promised, signalling of the DCC mode on 648 kHz has been corrected today :)
Btw the same mode (AMC 2, -6 dB) is signalled on 9410 kHz from Cyprus.
Best regards, Simone

andy.chance
20-12-2005, 19:29
Originally posted by simone

Hello John,
as promised, signalling of the DCC mode on 648 kHz has been corrected today :)
Btw the same mode (AMC 2, -6 dB) is signalled on 9410 kHz from Cyprus.
Best regards, Simone

Anyone know what the 2 (in AMC 2) refers to?

I thought 648kHz was still running DAM with 3dB carrier compression, not AMC with 6dB as is more common on HF.

Andy.

simone
20-12-2005, 19:40
Hi Andy,
I only know the definitions of the different AM carrier modes (1= -3dB, 2= -6dB), see attachment
Of course you experts at the Tx sites should know which mode you are using ;)
Maybe signalling on 648 kHz is currently wrong and they just used the same settings as for 9410 kHz, I was wondering that it was the same on HF and MF.
Simone

simone
27-12-2005, 15:46
Hi all,
seems there is still a problem with the DCC description on the BBC WS transmissions, since a few days they use again "no carrier control" instead of sginaling a wrong mode, see attachment
(btw same on 648 and 9410 kHz)
Simone

simone
03-01-2006, 15:16
Hi all,
the AMSS description on BBC WS 648 kHz has been changed today, now signalling DAM mode1, which probably is the correct mode on this transmission now.
Simone

PS: On HF from Cyprus it still is "no carrier control"

sveron
05-01-2006, 20:44
Hello to all,

The station ID has also been updated on 648//9410 kHz between wednesday afternoon and thursday night : from "BBC WS" it changed to "BBCWorld Service" as on DRM. Just noticed it tonight :-)

73, de Stephane

simone
06-01-2006, 10:59
... and here is an example what it looks like on 648 kHz after the changes yesterday
Simone

MikeB
24-01-2006, 11:46
Just published in the EBU technical review:

The AM Signalling System, AMSS — does your radio know what it is listening to?
Andrew Murphy and Ranulph Poole

The AM Signalling System (AMSS) adds a small amount of digital information to existing analogue AM broadcasts on short-, medium- and long-wave, giving similar functionality to that provided by the Radio Data System (RDS) on the FM bands. The system has been designed within the Digital Radio Mondiale (DRM) consortium, primarily to ease the transition from analogue to digital broadcasting.

A suitably-equipped receiver will allow selection of the AM service by name as well as the choice of re-tuning to other frequencies carrying analogue or digital versions of the same or a related service.

Several AMSS transmissions are already on air and some, if not all, of the first consumer DRM receivers will incorporate AMSS decoding.

http://www.ebu.ch/en/technical/trev/trev_305-murphy.pdf (507 KB)

simone
08-07-2006, 06:30
The country code information can also be sent in the AMSS but I only found it on the RTL transmission.
Also, the Roberts MP40 receiver can decode AMSS. I attach an example from BBC WS.

simone
08-07-2006, 20:31
... and only RTL are sending AFS region information, see attachment, but time/date are not being transmitted by any station until now.
Simone

dk8cb
08-07-2006, 21:20
... and only RTL are sending AFS region information, see attachment, ...

From looking at the screenshot and the target area for the FM transmission, one might believe that RTL's FM transmitter is on board a geostationary satellite...
:D

Roland

aru
09-07-2006, 15:46
For FM frequencies perhaps the better solution can be to define a RegionId without CIRAF zones, with the Latitude and Longitude of the tx site, and with a LatitudeExt and LongitudeExt of 1°.
This is the choice made by BBCWS for the Berlin frequency of 90.2 FM (see into AFS informations on all BBCWS DRM frequencies).

Aru

andimik
04-12-2006, 21:02
The station ID has also been updated on 648//9410 kHz between wednesday afternoon and thursday night : from "BBC WS" it changed to "BBCWorld Service" as on DRM. Now back again to "BBC WS"

26922

simone
04-12-2006, 21:09
The label was changed last week, but I wonder about the DCC mode in your attachment, before and after the change I always received DAM with 3dB, not 6dB on 648 kHz!
Simone

simone
07-01-2007, 11:59
RTL are also transmitting time/date information in the AMSS signal, which can now be displayed in Dream -thanks aru- unfortunately it seems the Roberts MP40 radio does not use this information to update its internal clock.
Also, seems time information is two minutes behind UTC and is updated every two minutes.
Simone

FritzWue
12-08-2007, 18:54
Just checked AMSS (Amplitude Modulation Signalling System) stations.
BBC WS is using higher bandwidth in AM, sounds good with the right IF and audio settings. :)
More info about AMSS:
http://www.ebu.ch/en/technical/trev/trev_305-murphy.pdf

simone
13-08-2007, 20:12
... and RTL added CT recently again :)
This could not be seen in the attachment above.
Also they are actually not using DAM2 (+6 dB) on MF!
@Fritz: Seems you are using a version of Dream that had a bug concerning the modes! This has been fixed a long time ago.
Simone

andimik
03-09-2007, 08:35
Thanks to a radio freak in Germany he found out that Truckradio is using AMSS on 531 kHz (remarks: AFS is not mentioning that frequency).

http://freenet-homepage.de/html-content/gif/531_kHz.gif

Maybe that's because they "recommend" their Truckbox ...

simone
03-09-2007, 14:45
I guess the mode in the attachment above is not correct.
Simone

edit Jan 22nd 2008: As the link above does not work anymore, I attach a screenshot from Dream.

pb1
27-10-2007, 11:35
From MySnip Radio Forum (http://forum.mysnip.de/):
AMSS: Habe gehört, dass nun auch Radio Australia und Radio Vatikan AMSS nutzen
Edit:
Because of this message, I was scanning my radio for other AMSS signals. I found that the BBC WS is now also using AMSS on 11760 and 15575 kHz analogue. Both from Cyprus (like the afternoon 9410 kHz broadcasts with AMSS). Also 5875 kHz from Cyprus (that is the 1800 UTC slot).

pb1
20-01-2008, 18:58
Hi,

My Morphy Richards did link two BBC Africa Service frequencies together: 15400 kHz and 11665 kHz. Can anyone obtain (using diferent tools) any info on signaling or AFS from these analogue frequencies?

pb1
23-02-2008, 09:21
AMSS on 15575 kHz is now back to BBCWorld Service, from BBC WS (from Cyprus)

OK1MJO
12-05-2008, 00:20
I receiving AMSS on 648kHz with Himalaya DRM2009:
http://www.ok1mjo.com/all/ostatni/t-dab_dvb-t_drm/prijimace/Himalaya/Himalaya2009_ok1mjo/AMSS



Martin

andimik
13-01-2010, 18:50
Since Summer 2009 RTL at 234 kHz seems to have lost the AMSS according to a German poster at ukwtv.de.

http://forum.mysnip.de/read.php?8773,562417,761094#msg-761094

The responsible person at Beidweiler told me, this was just a temporary test.

drmdab
02-08-2010, 20:32
By the way, RTL was back with AMSS when I checked some weeks ago. :)