Monitoring transmissions using a SDR receiver

When using digimodes you have to rely upon another amateur who can tell you if you signal is being over-modulated. Or, as per my previous blog entry, look at the ALC meter on the rig.
Another way of doing it is by using another computer in the shack (everybody has an old one!) and logging onto a Web SDR receiver somewhere on the internet.

There are many now and a quick search on Google reveals where they are.

Install Ham Radio Deluxe onto the old PC and set it in demo mode so you are only controlling a demo radio.
I found a piece of shareware software called Virtual Audio Cable that runs in demo mode.
Download it from here

Install it and launch the Audio Repeater part of it.
Set this to take the output of your audio card and feed it to the Virtual Audio Cable 1 as per this picture

Then set your sound mixer to have defaults similar to this

With this setting you will not
hear any audio through the speakers.

With this setting Line 1 is the input to the
DM750 module of HRD

Now when you use your favourite web browser to open a web SDR site you can tune it to the frequency your other PC (and the rig) will transmit on - make sure you set it to the correct sideband too (USB is normally used for PSK modes). Initially set the waterfall to the same audio frequencies on both PCs

Then transmit a CQ. If the SDR receiver is within range you should see your transmission. You may have to set the AFC (auto frequency control) on the DM780 to keep track. In practice I have found that the received frequency can be a few Hertz off from the transmitted frequency. This may be due to sky wave propagation or equipment tolerances.

I have used this to see if I am actually getting out to the countries I can actually hear on my rig, Most of the time it works but just like most things radio QRM or QSB can prevent your signal from being heard even though you can hear the recipient.