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| Polar Modulation Stereo System https://forums.stereotool.com/viewtopic.php?f=16&t=6233 |
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| Author: | radio700 [ Mon Oct 05, 2015 9:12 pm ] |
| Post subject: | Polar Modulation Stereo System |
Hi Hans, could you imagine for a project in the lower Fm Band 66-73 Mhz to support Polar Stereo with a Maximum deviation of 50 Khz? Tech Details here: https://www.google.by/url?q=https://www ... VWKIMbvrWA |
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| Author: | hvz [ Mon Jan 04, 2016 5:31 pm ] |
| Post subject: | Re: Polar Modulation Stereo System |
I don't really understand what this is or what it's used for. Could you give me some more info? I can try to Google it but since you asked for it you probably already know. |
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| Author: | radio700 [ Fri Jan 15, 2016 7:23 pm ] |
| Post subject: | Re: Polar Modulation Stereo System |
In eastern europe they use a different way of generating MPX Stereo for the lower FM band between 65-73 MHz. We have: 0-15 kHz L+R, 19 kHz Pilot, 38 kHz carriersuppressed AM L-R They use: 0-15 kHz L+R, 31,25 kHz Carrierreduced AM L-R They also have a maximum deviation of +/-50 kHz |
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| Author: | hvz [ Fri Jan 15, 2016 9:12 pm ] |
| Post subject: | Re: Polar Modulation Stereo System |
Ugh. No pilot? And what does 'carrier reduced' mean? More importantly, does anyone still use this? (Since nobody has asked me before). Are there radio's that can receive it? |
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| Author: | Doctor_Technical [ Sat Jan 16, 2016 10:09 pm ] |
| Post subject: | Re: Polar Modulation Stereo System |
From the frequencies mentioned by the original poster -- and indeed from the linked specification -- it sounds like the original poster is describing the now-mostly-obsolete "MTS" (Multichannel Television Sound) analog-TV stereo transmission system. The spec does mention a 1/2 f(sub) pilot injected at 8-10%... again that sure sounds like MTS, where the pilot was derived (and sync'd?) from the video's horizontal scan rate. Strictly as an engineering curiosity, how simple would it be for you to merely change the f(o) of Stereo Tool's pilot to 15.625 KHz and the modulating frequency of the L-R carrier to 31.250 KHz as the OP describes? You already have the ability to move the low-pass cutoff of the audio to what I recall as MTS's suggested 12.5 KHz -- although in a digital world, why not run it right up to 15 KHz?. The is one "glitch" with this idea -- there's always a glitch, right? -- in that MTS required aggressive preemphasis and DBX compression of the L-R subcarrier for noise-reduction purposes. Curling up with the Google Machine pointed to "MTS dbx specs" does makes for an interesting read, especially of the NAB Engineering Handbook section on the matter. Your question of "does anyone still use this" is quite appropriate, but on the other hand, I do recall marveling at the quality of MTS audio that was being shoved through already-ancient TV transmitters back in the 80's and 90's. |
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| Author: | hvz [ Sun Jan 17, 2016 12:50 am ] |
| Post subject: | Re: Polar Modulation Stereo System |
Changing the frequency of the L-R signal is not that difficult (although I would have to bypass some performance optimizations). But if this is very obsolete technology and also requires synchronization with a video signal (which I cannot do!), I don't really see the point. |
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| Author: | radio700 [ Wed Jan 20, 2016 12:46 pm ] |
| Post subject: | Re: Polar Modulation Stereo System |
No, it has nothing to do with television. It's FM Modulation for Stereo still used widely in the lower FM part (64-73 MHz) in Belarus, Russia and other CIS countries. Instead of having a Stereo Pilot sitting at 19 kHz and having a suppressed carrier at 38 kHz, Polar uses a Pilot at 31,25 kHz, but reduced by 14 dB Attachment: PolarFM.jpg [ 185.16 KiB | Viewed 13706 times ] Attachment: PolarRadios.jpg [ 104.38 KiB | Viewed 13706 times ] Attachment: PolarITU.png [ 58.38 KiB | Viewed 13706 times ] |
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| Author: | hvz [ Wed Jan 20, 2016 8:40 pm ] |
| Post subject: | Re: Polar Modulation Stereo System |
So, 1. If you broadcast normal stereo at these lower frequencies, radio's won't decode it? I really don't understand then why nobody has ever asked about it! 2. No RDS? 3. If I add this, can you test it? If you know of an SDR program that supports it I could test it myself as well. |
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| Author: | hvz [ Wed Jan 20, 2016 8:42 pm ] |
| Post subject: | Re: Polar Modulation Stereo System |
About 2.1.2.4: that appears to forbid using composite clipping?? |
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| Author: | radio700 [ Wed Jan 20, 2016 10:10 pm ] | ||
| Post subject: | Re: Polar Modulation Stereo System | ||
#1. If you broadcast normal stereo at these lower frequencies, radio's won't decode it? I really don't understand then why nobody has ever asked about it! Yes, with an OIRT Stereo Radio youll get only the mono portion of the signal (of course if you use a SDR that's different and works) #2. No RDS? Indeed no RDS. As the 57 kHz Carrier is not locked I don't know if there would be any noticable distortion when decoding... RDS would also be lacking of the Alternative Frequencies in this area. But RDS2 as far as I read would support them... Let's see what future brings #3. If I add this, can you test it? If you know of an SDR program that supports it I could test it myself as well. I don't have a polar-capable SDR program ready but a original OIRT transmitter and the corresponding tuner, so I could test it. As for clipping, I can't tell. Here is the full spec: https://www.utdallas.edu/~dlm/3350%20co ... !PDF-E.pdf
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