Bad habits

[Jack Crow]

Hi all,
This is going to be complicated. So work with me please.

Im mixing three hobbies into one project.

As most of you know, Im a radio geek.
One of those guys with too many antennas and nill social life.
And yes I do bathe.

I have recently discovered the thing called Virtual Railfan.
People go to areas where big trains do neat things, and set up automatic cameras to feed live video.
This link is for a 'diamond' crossing in Ohio.
https://www.youtube.com/watch?v=tVGIXLoQ-Fw

Now for some people this is as exciting as watching paint dry.
I learned a long time ago that watching the solvents boil out of pigments is not a sport for everyone.

This is not something I spend my nights watching like a hawk. More like background sound.
A chance to learn something new.

There is a 'chat' area where signed in members can exchange notes and information. They are a cool bunch.
They count cars and which power units are being used.
Some have the schedules and know what is coming when.
People from other parts of the world watch this stuff and comment on it.

Now the rub.

These cameras have microphones on them.
They are very good.
You can hear the wind in the trees, and if you leave the volume up on your speakers, get knocked out of you chair when a train horn goes off.
Part of that is Im using a big stereo unit as speakers for this computer. It has some power behind it.

Next level.
There is a 'scanner service' where some thoughtful soul set up a radio receiver that sends audio to the internet.
This is to catch the voice traffic for the dispatchers and crew in that area.
It works fairly well. Their problem is end users. Some speak loudly, some whisper, like the camera audio the volume levels are all over the dial.
https://www.broadcastify.com/listen/feed/26809/web

It was so bad that while watching this I had to keep adjusting the volume control to keep from going deaf.

There is a better way.

It's called audio compression.
The same method that is so annoying in tv commercials. As in why the adverts sound loud compared to the normal tv audio.
I use it here to level all this out.

Found a simple two transistor audio compressor on Youtube and made a 'stereo' edition.

Ego protection note here.
Just so you understand, this is a rev one, hand made circuit board.
Some might call it a haywire rig.
It's not going to look finished or refined.
No rev one product will ever look perfect. Just ain't going to happen in the human universe.

The compressor effect is now most every sound is at the same audio level.
The horns make as much noise as the wind in the trees.
Same for the radio traffic.
No more ear abuse.

Not constantly on the volume control. This is a major advantage.
Guess you could say "there I fixed it".

This is the back view. Ok, not too exciting.
10-27-2017 003.JPG

The inside view.
To quote Thomas Dolby 'all my tubes and wires!'
10-27-2017 004.JPG

Close up of the hand made prototype board under test.
Get the first side of a stereo circuit to work right, built the second side to match later.
10-23-2017 008.JPG

Front view.
The bar graph is a bit of un necessary swank.
In service it looks cool.
This thing takes the full level from the computers sound card w/o a major problem.
The switches will select 'compress' and 'by pass' modes.

10-27-2017 001.JPG

This is where my inner nerd is going to show up.
The output level has not gone past -29dBm on my bench milivolter.
No matter how loud the input.
That is how compression works, think of it as 'this and no more'.
10-23-2017 005.JPG
I know that VU and dBm don't line up.
There is a big article on the wiki about it if you want to split hairs.

I have it running right now. Works well.
I think it can be improved from a user function point of view.
The idea was to mount it to the side of the stereo amp Im using.
So the input and output connectors will have to go on the back.
Same for the power jack. I may install it in the stereo and loose the housing completely.
Time will tell.

Thinking about making a simple etched circuit board.
The proto board was ok for a 'one of' but if this thing catches on, circuit board is the way to go.

Need to put the internal wire work on connectors, all that clunky hand soldering looks so 'seventh grade'.
I can do better.

For now Im going to run it for a few weeks and see how it holds up.

Be well all.
Jack Crow aka Radio Mike in Virginia Beach

[Mooselake]

You can never have too many antennas or radios, just not enough space to mount them all...

Don't forget the local amateur radio club for social life - if we have one here in MooseVille your's is probably a lot bigger. Lots of radio geeks there

Kirk

[Jack Crow]

Hi Kirk,
Good to hear from you.
If you can, punch up the links and let me know what you think about the stock audio levels.
Suspect the scanner audio is a mix of wide and narrow FM signals plus the usual front end overloads.

Keep it sane.
Jack Crow

[RetireeJay]

Could you provide a link to the audio compressor circuit? Many, many years ago, I tried to design a compressor myself. If I "broke the loop" and just used a potentiometer to create the simulated level of compression, the circuit worked wonderfully; it had a huge range and no distortion at any level. But whenever I closed the loop and let the circuit try to do the compression on its own, it just kept cycling between little compression and lots of compression regardless of input.

[Jack Crow]

RJ
One link, coming up.
https://www.youtube.com/watch?v=pUii_pDQxg8&t=16s

This works fairly well.
There are two articles in the series.
One is the full blown engineer version with the fancy multi channel scope, and this one connected to a scanning receiver.

Keep it sane.
Jack Crow

[Mooselake]

I didn't see a post-compression link, but the one to broadcastify sounds pretty good and with adequate level control for the short time I listened. Something seems to have introduced a strong southern accent, though

We've had ALC, AGC, etc. circuits for many years, and software equivalents for some time, but when switching from Netflix to YouTube on a Roku it wants to blast us out (well, me, Mrs. Moose isn't much on AvE or that Australian electronics guy Dave) of the room, and that's with compression enabled on the (must be around mid aughts) home theater system

Kirk