Stereo encoder not working

[Slipmatt1]

hi I just bought a stereo encoder and the audio sounds terrible it a NRG vironica one. audio fine in mono. just wondered if anyone else had problems with stereo encoder

[Slipmatt1]

I have noticed that no Pirates broadcast in stereo I was wondering why

[LeeCavanagh]

Have you set the levels and have you set the audio pre emphasis (if your not doing it elswhere). There will be two that you can set to 50us, but turn off the pre emphasis on your TX if you have one there too.
Please show a picture if you want further help

[Slipmatt1]

hi mate its this one

099A1CD6-80C9-4D78-BADE-BACAF54F9315.jpeg

[Slipmatt1]

just so much bad noise comes through but OK in mono

[Slipmatt1]

my link box sounds fine until I connect stereo and it just goes all out the window. it's not my transmitter because I'll get it coming out of my Sat can as well same noise.

[LeeCavanagh]

The encoder is decent enough, they work well for the price, if you don’t mind which is left and right.

Turn the volume down, then slowly turn it up until the stereo light comes on

Can you describe the audio? Or attach a recording
The thing is, we don’t know how you have set everything up, the link TX does that have pre-emphasis? If so turn it off, you only want the stereo encoder to do the ore-emphasis, adding twice would make it sound awful (but I don’t know if that’s what your hearing or something else)

The other possibility is that RF could be affecting tour audio, but that is difficult to say from here

[teckniqs]

I remember those olf things from the mid 90s, if I remember correctly from back on the old Y2K Pirates forum people were building a seperate 'Brickwall Filter' PCB for these because the separation was so bad.

....I tried using one just like this back in about 1996 from a little rig running direct and it even hissed in the same house lol.

[LeeCavanagh]

Ive used them and found them to be fine, the separation specs are fine, also how does a brick wall filter help separation? I understand it would help with explosives and the like, but not with separation , its not going to improve things in that respect, if you have junk in though you will get junk out, keep your audio under control from the outset and these are more than adequate. What do you use for your audio processing? Do you have a agc/ limiter in your link TX? If so maybe it’s going a bit crazy trying to adjust for the mpx signal. Ive even used these with RDS and it was all happy together. Let us know how you get on. I’m betting the levels are all that’s needed.

[teckniqs]

Well I very much doubt they would have gone out of their way to bother making one up and fitting one if it didn't need one, but you're the expert.

[LeeCavanagh]

Well I very much doubt they would have gone out of their way to bother making one up and fitting one if it didn't need one, but you're the expert.

Not claiming to be the expert ,don’t worry techniqs, but i certainly used one without any issues so that feels relevant to me to mention, with a wide range of programme source material too. Maybe they needed the extra filter because of uncontrolled levels to start with, I could not even begin to guess, if you have the circuit for the mod then maybe the op will want to give it a go... we still don’t know what type of artefacts he’s hearing in the audio, so we are all a bit blind, I hope he’s fixed it though, last thing I want to do is annoy you. (Group hug)

[MiXiN]

hi mate its this one099A1CD6-80C9-4D78-BADE-BACAF54F9315.jpeg

I built one of these about 5 years ago, and I'm sure there was some faint high frequency tone audible when it was set to stereo mode. The tone was about 16 > 18Khz and annoying.

In mono it sounded OK.

As Teckniqs said, I also recall having to use a 15khz brickwall filter because high frequencies like cymbals made the audio sound bad & scratchy.

The brickwall filter was built on a red PCB, and it was from some guy on here based in the Netherlands I think - Katruud is it, Teckniqs?

[mikroman]

i used this encoder 20+ years ago. The noise problem can be caused by high pilot levels. If you have no other way to measure the pilot level, as suggested you connect a potentiometer between the stereo encoder and the mpx input to the link. Turn the potentiometer slightly until the stereo lamp on the receiver appears. Another cause of noise can be a bad PC card combined with a lack of brickwall filters. Next, the author of this toy missed the preemphasis curve. At 15KHz there is -3dB rolloff. Another disadvantage is that the encoder swap the left and right channels after restart. And yes, the separation really breaks down when the audio material enters the pilot area. When you correct emphasis curve, with a good sound card and broadcast software with LPF encoder sounds ok, but still a few steps better variant is software defined stereo encoder and 192KHz sound card (decent entery level costs less than 80 euros)

PS
an unfiltered switch power supply can also make a mess in the composite baseband

[yellowbeard]

hi mate its this one099A1CD6-80C9-4D78-BADE-BACAF54F9315.jpeg

I built one of these about 5 years ago, and I'm sure there was some faint high frequency tone audible when it was set to stereo mode. The tone was about 16 > 18Khz and annoying.

In mono it sounded OK.

As Teckniqs said, I also recall having to use a 15khz brickwall filter because high frequencies like cymbals made the audio sound bad & scratchy.

The brickwall filter was built on a red PCB, and it was from some guy on here based in the Netherlands I think - Katruud is it, Teckniqs?

https://www.amateurradioshop.nl/webshop/katruud/

[MiXiN]

hi mate its this one099A1CD6-80C9-4D78-BADE-BACAF54F9315.jpeg

I built one of these about 5 years ago, and I'm sure there was some faint high frequency tone audible when it was set to stereo mode. The tone was about 16 > 18Khz and annoying.

In mono it sounded OK.

As Teckniqs said, I also recall having to use a 15khz brickwall filter because high frequencies like cymbals made the audio sound bad & scratchy.

The brickwall filter was built on a red PCB, and it was from some guy on here based in the Netherlands I think - Katruud is it, Teckniqs?

https://www.amateurradioshop.nl/webshop/katruud/

Didn't realise Amateurradioshop sold Katruud gear.

Katruud used to be on here, but he's not logged in for ages. Bought a few things from him years ago & it was quality gear.

[Albert H]

That's the silly "stereo coder" that doesn't know its left from right! It's also a pretty poor layout, and has huge problems with letting 4864kHz crystal clock get on to the output, causing big nasty spurs 4864 kHz either side of your carrier.

[radium98]

found on the net brickwall filter maybe close to katruud

[Albert H]

A brickwall audio filter won't help the fundamental problem with this crappy coder. The layout is appalling, and it leaks a huge amount of the crystal frequency (4864kHz) into the multiplex output. This will appear as spurs either side of your carrier!

Build a proper stereo coder. They're trivially easy to get right. If you have the audio filter, and you have the 4864kHz crystal (you can steal it out of the crappy Veronica "coder" board), I'll happily give you a circuit that's easy to build, easy to get right, and gives great separation and low distortion.

The best stereo coders that I've used do not use the switching approach, but actually go the analogue route, and generate a proper DSSC difference subcarrier and a sinewave pilot tone.

[LeeCavanagh]

Albert, does that mean you have found the circuit?

[Slipmatt1]

just got it all working. with a nrg kit pro 3 driver sounds ok it was the pre emphasis now disabled all good.