MDSR Software IF interface with FT-857d through Xonar U7 usb sound card, and Asus T100

This is going to get complicated.  My plan for this blog entry, (or maybe a couple) is to explain the what and how...I do this a lot, but this one is particularly complex (not difficult) and it took me a while to decipher the docs and troubleshoot.

MDSR
MDSR Yahoo Group

Background is there are a number of SDRs (software defined radio) out there with costs from $40 for a receive only dongle (RTL-SDR) to $3000 worth of Flex-Radio or the equivalent.  But there isn't much in between.


Some very smart folks figured out that you could pull (in many cases) a 455kHz IF (intermediate frequency, a tool the radio uses to give it multi-band capability...and probably other reasons an EE could explain) from many lower cost commercial amateur radios.

With the IF output, you now have all the audio for whatever band the radio is on...the radio does the heavy lifting, and you play with the output.

The folks at Modulator-Demodulator Software Radio created some circuitry and software to take that IF output, bring it down to around 12kHz and then let the software create the waterfall effect and other things (like filters).  Tuning through the bands looking for signals is more fun with a waterfall display.  (uses Omni-Rig and my CAT cable for the interface)

The RX hardware is called Lif2014, it can be used stand alone (that is as far as I have gotten).  The TX part is called BiLif, and the Lif plugs into it for RX/TX capability.  With this hardware, you don't need TNCs or other hardware to use digital modes.

The software is called MDSR.

1) Radio

Here is my setup.  A Yaesu FT-857d to supply the IF.  I got a short chunk of small coax with a BNC on one end.  for the other end, I bought a 4 pin header with 2mm spacing.

The easy part (and one reason I bought this radio) is there are two blank plugin spots for filters.

The coax center conductor is soldered to the 'inside' pin (left pin of the set of 4 in the above picture) and the ground shield is soldered to the 3 outboard pins of the header...then header plugged onto filter pins.  So no permanent mod to the radio.

 

By wiring it up that way you enable the filter in the radio menus...so you can turn the mod on and off.  One possible drawback would be that you lose audio out of the radio speaker while the filter (IF output) is engaged...disengage it again, and you have normal use of the radio audio output.

Note that the audio will be supplied by the IF converter and your sound card...so voice modes are still available, just through the computer speakers (or headphone jack).

2) IF converter (Lif2014)

This kit (available on the MDSR website) is a fairly easy build with no testing equipment required (other than a voltmeter).  The labeling on the some of the components was hard to decipher, so I will include my notes on that.  The unit requires 12vdc, I am using a 500ma wall wart for now.  (note, mine is the 2012 version, but the circuitry/operation/software is identical...just the layout changed a tiny bit)

3) Sound card

Here is where it starts getting tricky.  To use the equipment I have listed so far, you can simply plug the Lif output into your computers sound card and have at it.  If you want to transmit, you will need a good sound card.  If you want to use digital modes also, you will need a second sound card.

The solution to all that is the Asus Xonar U7, a USB sound card.  The MDSR folks have tested it and found that it is within limits for transmitting, so you can use it as your audio out...in addition it adds a sound card, so you can use your internal sound card (for example in a laptop) for digital mode decoding, and the Xonar for the MDSR software work.

This is the biggest headache I had on this hole job...getting my desktop sound card line inputs to work properly...I haven't tried it on a laptop yet.

So I have a standard mini stereo jack going from the Lif 12kHz output to the Xonar linein/mic input.  On the back of the Xonar I have a RCA to mini stereo cable going to my desktop line-in port.

(missing in the above pics are the input properties...where you select "Listen to this Device" and the output you want to use)

Again, this is so MDSR software can have the audio out of the Xonar, and programs like Fldigi can have the audio out of the computer sound card.

4) Software

Of course the Xonar required its software and drivers, but it works well, no problems with installation or use.
MDSR  has to be installed with the latest updates.  And some digital mode software if you want to play with that.


The MDSR software itself is functional, but it relies on java, and is sluggish (on my fast desktop).  They are working on an all new software package, that should solve those problems.

If you made it this far...I have successfully run this setup on my Asus T100 Transformer.  I don't have a USB hub handy, so I haven't used the CAT control with it (only one USB socket), I also have not put audio into the Transformers sound card...and I am assuming it has an audio in...

to be continued...  Part 2

BTW here is the screen shot that all the above closeups came from...