AM STEREO DECIDER

[rigmo]

Hi
Question
Albert H an all. Do you heave good AM STEREO DECODER?
What is better MC13020 or MC13028?

http://meduci.com/
https://rf-circuit-schematic.blogspot.c ... 13028.html
http://www.aspisys.com/dqam_manual.pdf

[Albert H]

None of them - they're all horrible! AM stereo was never more than a silly gimmick, which never really took off. The biggest radio markets around the world were moving to AM for talk stations and FM for music, so AM stereo largely died out.

The American channelling on MW - 10 kHz - gives a chance of slightly better sounding audio, but in Europe, the 9kHz spacing makes audio bandwidth a bit tighter. AM stereo also uses a wider channel width, so would have been impractical in Europe because of the high numbers of stations (at the time) crammed into a limited number of possible frequencies.

AM also has the interference problem. FM invariably sounds better because as long as the signal strength is enough, the limiting action of the IF strip in the average FM receiver will eliminate most interference signals. AM, on the other hand, is prone to all sorts of pops bangs and crackles....

To quote Steely Dan: "FM, No Static At All"!

[Zozo]

Ultimately Motorola's C-QUAM has the largest populatiry when it comes to Stereo-AM. Even Dreamradio AM in the Netherlands only upgraded to stereo on 1485KHz in February last year; They also opted for C-QUAM encoding.

I have a few Stereo capable AM receivers I purchased from a Japanese auction site which is the best option in my option, rather than modifying receivers with decoders. However the Meduci has the largest support / help docs I'd say.

Stereo-AM is still largely used in the United States, Canada and Australia. However there are still some in the following countries: Philippines, Japan, Thailand, South Korea, Italy & Brazil.

[Zozo]

This video is a direct feed from the receiver, you can certainly hear the separation.

[fmuser877]

I wonder if DAB+ stereo will be better nowdays

[Albert H]

I wonder if DAB+ stereo will be better nowdays

Not really. I've recently put a number of DAB+ stations on the air, and the audio quality is generally disappointing - mostly because the distribution companies are trying to cram ever more stations into their limited bandwidth.

Theory suggests that - assuming you have a good sample rate - that the quality of DAB+ should be close to that of a CD, but in reality the coding and decoding process is less than perfect, and a quick test we tried was to have the same material played direct, on FM stereo, and on DAB+. We had a bunch of listeners - in the same listening room - fill in a chart with the mode that they thought each music snippet was being played by....

All of them could identify the DAB+ almost every time (91%), FM Stereo about 40% of the time, and direct CD about 60% of the time. The digital artefacts of the DAB+ coding process are almost always audible.

A while ago, we tried some similar listening tests with various different audio encoding schemes, including WAV, AAC, FLAC, Ogg, MP3 and Dirac. ALL of them were reasonably obvious, but when we asked for preferences, our panel usually chose WAV or FLAC, with higher bit-rate Ogg not too far behind!

We ran a similar set of tests with broadcast professionals at an EBU meeting in Geneva, and everyone chose FLAC and WAV as their preferences. All of them could (usually) identify the codec they were listening to!

[Albert H]

This video is a direct feed from the receiver, you can certainly hear the separation.

Unfortunately, it's NOT actual broadcasting you're seeing - it's a little AM Stereo exciter connected directly to the receiver. Unfortunately, in the Real World™, the vagaries of AM make the results rather less than acceptable listening quality! Most of the broadcasters in the USA that tried it abandoned it as their music services left AM. It's pointless for talk shows!

[radionortheast]

I suppose records have come back into fashion maybe people could take to hearing bangs and whistles bit of snap crackle and pop

[radionortheast]

I do find am stereo interesting, with fm nothing interesting could reach the uk with tropospheric reception, there are no high power pirates on fm that could reach the uk as there used to be in Ireland, it would be nice to hear a stereo signal coming 100's of miles on a regular basis. Sporadic e allows reception of stations 100’s of miles away it is unreliable only happening afew months during the summer, more of a nusiance. Am you have the skywave which makes it reliable, its nice to think there might be something out there interesting one day coming through the noise..with there not been much of an audience around and no receivers that could receive the stereo signal I suppose it is a bit of a day dream.

[outis]

None of them - they're all horrible! AM stereo was never more than a silly gimmick, which never really took off. The biggest radio markets around the world were moving to AM for talk stations and FM for music, so AM stereo largely died out.

The American channelling on MW - 10 kHz - gives a chance of slightly better sounding audio, but in Europe, the 9kHz spacing makes audio bandwidth a bit tighter. AM stereo also uses a wider channel width, so would have been impractical in Europe because of the high numbers of stations (at the time) crammed into a limited number of possible frequencies.

AM also has the interference problem. FM invariably sounds better because as long as the signal strength is enough, the limiting action of the IF strip in the average FM receiver will eliminate most interference signals. AM, on the other hand, is prone to all sorts of pops bangs and crackles....

To quote Steely Dan: "FM, No Static At All"!

I do have and AM Stereo capable radio - AMAX certified Sony SFR-42 - and it is more than a gimmick. It kind of took off in the US for a while and it is probably still a thing in SE Asia/Japan, maybe Australia too.
I was using it earlier today for R. Caroline, and AM definitely sounds better - even the non-stereo stations.
I used to use it in France and Greece where there were AM-Stations. There are no such in France now.
For Europe a WideAM radio I think will be as good, if not better. Although I have tried the Sangean ATS-909 in its wide setting and wasn't impressed. The only radios in which I found AM sound impressing are the vintage Roberts R600, R707 and (slightly less) the later R900. There are other too.
So if one today wants quality AM sound the way is some older HiFi AM receivers and other vintage radios as above, rather than an am-stereo decoder.

PS. I can understand why treble is not very good on AM - but why bass isn't either? The bandwidth is there...

[Albert H]

AM stations usually roll off the bass end because most receivers won't reproduce deep bass, and there's little point in wasting energy in transmitting audio content that won't be audible!

[outis]

AM stations usually roll off the bass end because most receivers won't reproduce deep bass, and there's little point in wasting energy in transmitting audio content that won't be audible!

But why the FM don't? It's usually the same radio.

[Albert H]

Commercial FM stations often roll off at around 60 Hz.

AM transmitter power requirements are proportional to the frequency of the modulating signal, because lower frequencies convey the most energy. Rolling off the bass allows greater "talk power" with the transmitted energy being more predominant in the "speech band".

[outis]

Commercial FM stations often roll off at around 60 Hz.

AM transmitter power requirements are proportional to the frequency of the modulating signal, because lower frequencies convey the most energy. Rolling off the bass allows greater "talk power" with the transmitted energy being more predominant in the "speech band".

Thank you, which explains why my own AM transmitters sound s much better! But then there are some radios (like the old Roberts R700) that have quite better bass than others for the same stations. So it's on the radio too.

[Albert H]

Back in the offshore days, it was quite common for some of the transmitter engineers to "open out" the transmitted bandwidth in an effort to improve the perceived audio quality. The "Ampliphase™" transmitters could be set up to transmit audio down to ~45Hz and as high as 9 kHz, so they tended to "splatter" adjacent frequencies. I would always adjust for a midrange and treble boost, with a tight roll-off at 7k5Hz, and a bit of bass boost. It wasn't "FM" quality, but it sounded better than most of the competition!

[Nige from Brum]

You should hear some of the Dutch MW pirates that operate between 1620 & 1700 KHz. Many of them transmit almost HiFi AM signals if you have a good receiver & speaker set up. I'm often amazed that there is actually some bass that I didn't realise was possible with AM.

Sadly modern receivers & restrictions on bandwidths imposed on legal stations really hamper the sound quality.

[outis]

You should hear some of the Dutch MW pirates that operate between 1620 & 1700 KHz. Many of them transmit almost HiFi AM signals if you have a good receiver & speaker set up. I'm often amazed that there is actually some bass that I didn't realise was possible with AM.

Sadly modern receivers & restrictions on bandwidths imposed on legal stations really hamper the sound quality.

It is mostly to the receiver - in my view - than any audio processing, because there are receivers giving good audio whatever is the station transmitting bandwidth. So it isn't so only what the station bandwidth is. And to return to the topic: it's much better to find one of these radios (an easier too) than to try AM Stereo or the modern radios that offer a "wide" AM option.
I have tried a ...wide range of radios, vintage, valve, transistor, crystal (!), modern, portable, pocket, sound system tuners, and tuned to a variety of stations looking for the "ultimate" AM/MW experience. So far nothing beats late 50s valve radios or mid to later 60s Roberts radios (although I guess the Hackers are most likely as good). Then come the AMAX/AM Stereo, then the radios with "wide" setting options or "extra bass". What I haven't tried so far is those HiFi AM radios of the 60s and early 1970s.

[outis]

Back in the offshore days, it was quite common for some of the transmitter engineers to "open out" the transmitted bandwidth in an effort to improve the perceived audio quality. The "Ampliphase™" transmitters could be set up to transmit audio down to ~45Hz and as high as 9 kHz, so they tended to "splatter" adjacent frequencies. I would always adjust for a midrange and treble boost, with a tight roll-off at 7k5Hz, and a bit of bass boost. It wasn't "FM" quality, but it sounded better than most of the competition!

No matter how much one "opens up" the modern radios are just not up to the task. And also the AM/MW content isn't great.
The best option is to find the content one wants then use a "pantry transmitter" with no bandwidth filtering at all and send it to a good vintage radio. For the listening experience. If one wants a broadcaster experience one can use something more powerful of course!