Decoding using Dream - Sound settings?

[Reece]

Hi, my first post here!! Greetings to all.
I have been decoding utility stations on and off for many years and recently experimenting with a 144Khz/12Khz IF decoder using Dream, this produces very clear signals with the ability to narrow the bandwidth without expensive radio filters.
However the problem is all/most software require an audio in through a sound port rather than the current desktop sound, I can only think of a connection from the current sound port out to another sound card input, would this work or is there a better method?
Thanks.

 

[ka3jjz]

I'm unsure what you mean by a 'current desktop sound'. I've fooled around with DREAM, and that's not how you hook it up.

You would make a connection between the 12khz IF directly to a input on your sound card on the PC. Some folks find it necessary to put a small audio taper pot in the line to control the level, as DREAM is very sensitive to being overdriven.

Some radios come with a tap already built in (the TenTec RX320D has one, for example, as does the new R8T from Alinco), and some need to be modified to make this work. What radio(s) are you planning to use for this app?

Mike

 

[Reece]

Sorry I didn't explain it well, as you say the 12khz output plugs into the radio's sound card input, Dream then decodes it and sends it out to the computers system sound or the sound card's output.
Problem is a decoder for fax/morse/rtty etc requires a sound card input, seems I would need another sound card, then send the current dream output to the morse decoder input, this is the problem.
I hope I explained it better (probably not, it is rather hard to explain!)

 

[ka3jjz]

I had exactly the same problem - and had the parts in my junkbox to solve it. Build a simple switchbox with a couple of inputs - one for the 12khz IF, the other for your audio out (for the digital decoder) (I'd have 3 or 4 inputs in case I had other things I wanted the soundcard to do). The output from the switchbox goes to your sound card. This makes it quite easy to add a pot in line with the IF in, in the case you need to be able to adjust the IF level to avoid the overdriving issue (it seems that some radios do, others don't - I still don't know which radio you hope to use with DREAM...). No special construction issues here - any old plastic junkbox will do, the jacks, pot and switches should be easy to find.

A pretty simple and easy project to build - this is a great starter project, if you've never done anything like that before. I wish I had the time to do more of that, frankly...

Mike

 

[Reece]

Hi, thanks for that, the radio I use is a Kenwood R-5000, I built the decoder as a kit! Making a switchbox is easy enough but seems there will be a problem having the same input for the 12Khz IF and the decoded morse signal at the same time since both will need to be active to work.
Then again maybe not!!

 

[ka3jjz]

Why would both need to be active? You wouldn't use the 12khz IF signal for your morse decoder - that would be fed from a line out, which is usually a fixed level audio output (as opposed to a speaker out, which is not fixed). You would not need both to be active - it simply doesn't work that way.

In addition I doubt that there is any decoder program that works off the IF output - it's certainly a possibility but I don't think it exists. Check the link in my sig for a pretty comprehensive list of such programs. Most all of them use a fixed level audio output to produce results (there are a couple that can use the IQ output of a radio, such as that found on the R8T).

Now if you were trying to do 2 things at once (DRM and digital at the same time), then you would need 2 soundcards (as you earlier surmised), but you'd have to insure that you could address the 2 soundcards differently. I would think the CPU load would be quite high - DRM can suck a lot of resources on top of whatever digital decoding program you might run. It's doable but I think you're trying to do too much at once...Mike

 

[Reece]

Hi Mike, yes the link you give is to utility decoding software these require a sound card input, the 144Khz IF out of the radio requires a sound card input, both have to be active at the same time if you want to decode signals from the Dream decoder since (shown below) these are better than the radio output:

The sound from the above is coming out of the system desktop speakers, this needs to be decoded.

 

[ka3jjz]

You got me on that one - never heard of anyone doing this, in this particular manner....Mike