PRO 3 Stereo Coder

[sinus trouble]

Hello Necks!
I have searched the NET far and wide for info on this PCB and had no luck!
However! I believe it is very similar to the design Sir Moss used on his 1 - 5 Watt VFOs which I happen to have!
The PRO 4 is truly superior but I like the simplicity and it is genius the way it works!
Pisses all over most basic coders out there today!
Anyway I thought id share my first copy! Parts list and layout to follow!

003 - Copy.jpg

[nrgkits.nz]

Here's the original manual:
http://www.gareth.net.nz/nrgdocs/Pro3_Stereo_Coder.pdf

I have gerber files, will upload them later

[Albert H]

Note - there is an error in the circuit diagram (my fault, I'm afraid). The pre-emphasis resistors should be 47k on both channels. One of them is incorrectly marked 4k7. The components on the PCB layout and in the parts list are correct.

There is one simple (and cheap) improvement that you can make to this coder - replace the CD4016 with a CD4066. This will reduce distortion from about 1% down to 0.1%. The 4066 is a pin-for-pin drop-in replacement.

[sinus trouble]

Here's the original manual:

You are the man Mr NZ!!! Much appreciated!
I did not realize there was a mono/stereo select jumper which is handy! I learn something new everyday!

[sinus trouble]

Note - there is an error in the circuit diagram (my fault, I'm afraid). The pre-emphasis resistors should be 47k on both channels. One of them is incorrectly marked 4k7. The components on the PCB layout and in the parts list are correct.

Dear dear! Amateur error Mr Albert!
I think I recollect you mentioning that you assisted Sir Moss on most of the NRG projects! Salute to you both for these legendary creations!

[sinus trouble]

There is one simple (and cheap) improvement that you can make to this coder - replace the CD4016 with a CD4066. This will reduce distortion from about 1% down to 0.1%. The 4066 is a pin-for-pin drop-in replacement.

Cheers Mr Albert! I will do just that! Cricklewood electronics is not far from me so I shall pop in there some time next week!
Unfortunately they don't stock the 4.864mhz crystals They do have some other interesting stuff like trim coils etc which I have been meaning to get for some time now!
Enigma seem to have the correct crystals and other bits in stock so I will be contacting them soon!

[nrgkits.nz]

I have a bag full of 4.864mhz crystals I picked up from www.taobao.com for next to nothing

[Albert H]

Note - there is an error in the circuit diagram (my fault, I'm afraid). The pre-emphasis resistors should be 47k on both channels. One of them is incorrectly marked 4k7. The components on the PCB layout and in the parts list are correct.

Dear dear! Amateur error Mr Albert!
I think I recollect you mentioning that you assisted Sir Moss on most of the NRG projects! Salute to you both for these legendary creations!

The Pro II coder was Stephen's design, and he came up with the neat little square PCB for it. There was a problem with the coder, though in that the input sockets would be right and left randomly - each time you switched it on, there was a 50 : 50 chance that the channels would be the wrong way around!

I came up with a couple of simple modifications - using the reset input of the 4013 during start-up and guaranteeing that the bistable would always switch in the right "sense", allowing the input sockets to be labelled "left" and "right". The other modification involved adding some extra diodes, with two of them forcing both channels "on" in mono mode, and suppressing the pilot tone. The one-wire switch to make the LEDs change over was also my idea. These modifications were added to differentiate Stephen's product from the "Veronica" effort down the road, and they added virtually nothing to the component costs, but improved the function of the coder markedly.

We found some nice bi-colour LEDs that we used in ready-built gear - when you flipped the mono / stereo switch, the LED changed colour. We also used these for the simple modulation indicator that I came up with - green for OK level, and red for peaks.

I also came up with a two-LED indicator for adjusting the VCO trimmer, using an op-amp, and using the 5V supply to derive the reference. We planned to include this on the next run of PCBs, since many users found that adjustment to be tricky.

[Electronically]

I've had one of those circuits .When balancing the right and left audio there not so good one sounds louder than other when there balanced they go off balance at times on its own .bit of a pain really not worth putting one of these together .

Sent from my SM-G900F using Tapatalk

[Albert H]

The Pro III is simple to set up. Just put a tone into both channels in turn, adjusting the presets for the peak deviation you want, making sure that both channels deviate the same. Done!

[Electronically]

tried that .When it was balanced it would sound slightly louder on one side and other wasn't so good after a couple minutes .Veronica stereo decoder wasn't that good .The very first one they had was good .

Sent from my SM-G900F using Tapatalk

[shorty]

Scans of the silk screen and track side of a pro 3 coder

[Electronically]

Scans of the silk screen and track side of a pro 3 coder

confused I thought it was stereo coder pro 2 from veronica .But I've never tried this board .Where do I get my hands on one them ?

Sent from my SM-G900F using Tapatalk

[Electronically]

Sorry Albert I've mixed up with veronica board .But I've not tried pro 3 board .

The Pro III is simple to set up. Just put a tone into both channels in turn, adjusting the presets for the peak deviation you want, making sure that both channels deviate the same. Done!

Sent from my SM-G900F using Tapatalk

[nrgkits.nz]

Here's the gerber files I use:
http://www.gareth.net.nz/nrgdocs/nrg/pro_3_coder/

And you can easily get 4.864MHz crystals from Aliexpress also:
https://tinyurl.com/y8apezs4

You also need set the padding capacitors for different batches of crystals, you need a scope or freq counter for this but will ensure its operating spot on 4.864MHz

[sinus trouble]

Scans of the silk screen and track side of a pro 3 coder

Nice quality scans Mr Shorty! I think I will scrap my earlier version and copy those!

[sinus trouble]

Here's the gerber files I use:

And you can easily get 4.864MHz crystals from Aliexpress also:

You also need set the padding capacitors for different batches of crystals, you need a scope or freq counter for this but will ensure its operating spot on 4.864MHz

Blimey!! 100 crystals for less than a fiver!! That Aliexpress is really cheap!
Too many crystals for me though lol! Do you still produce the coders?
I do like the PAs you had too! Neat! Even the steel housings are impressive!

[Albert H]

Scans of the silk screen and track side of a pro 3 coder

confused I thought it was stereo coder pro 2 from veronica .But I've never tried this board .Where do I get my hands on one them ?

Sent from my SM-G900F using Tapatalk

Gareth in New Zealand may be able to help you with a PCB. I have built them on Veroboard - that's how the first prototypes were done. There is a Version Pro IIIb that Stephen and I had done - the only change was to use the last op-amp in the TL074 to develop the ½-rail for the input stages and the output filter. We also considered adding a bit more filtering to the output to make it a bit cleaner, but found that there was little benefit in the additional complexity.

I think that I've got a Veroboard layout for one of these somewhere. I'll dig it out an post it on here.