Using an external SDR as a high resolution panadaptor

OK, so the FTdx101 series of radios has an excellent panadaptor function via the screen on the front panel plus the external screen that can be plugged into the DVI socket on the rear panel. But the screen resolution is only moderate and there are benefits that can be had by connecting an external SDR unit such as an SDRPlay RSP1A. A unit such as this works with an application on the shack PC which processes the output of the SDR, tuning it to the required frequency, demodulating the RF and applying functions such as noise reduction and filtering.

The Ftdx101 has excellent support for an external SDR with sockets on the back panel for both RF and IF outputs to drive the receiver. I originally used an SDRPlay RSP1A connected to the RF output of the main receiver. I've subsequently upgraded that to an SDRPlay RSP Duo which has two independent receivers. The RSP Duo receivers are coherent and will support true diversity reception with appropriate software. The two receivers of the RSP Duo connect to the two RF outputs of the FTdx101D and the diversity function of SDRUno virtually deletes most local QRN.

The two leading SDR applications for Windows are SDR Console and SDR Uno. When paired up with a suitable SDR, these can make your PC function as a very nice general coverage receiver spanning frequencies from Long Wave all the way up to microwaves. They also include functions that will allow them to be interfaced to many modern HF transceivers to provide a high resolution panadaptor and/or an additional receiver.

Both SDR Uno and SDR Console include a function to synchronize themselves with an attached transceiver - including an FTdx101D. When this function is enabled, the tuning of the SDR application and the transceiver are locked together - spin the dial of the FTdx101D and the application on the PC will follow the tuned frequency, retune the PC application using the mouse wheel or keyboard and the FTdx101D will follow it.

If all you want is a better panadaptor, then the configuration is simple. Both SDR Console and SDR Uno make use of OmniRig as the interface for this synchronization. You need to install the SDR application of choice, install OmniRig, create a virtual port pair following the instructions here, configure one end of that virtual port pair into 101Cats and the other end into OmniRig. Finally, configure your SDR application to synchronize via OmniRig and it will all work well.

The issue comes if you want to sometimes use the SDR application as an additional independent receiver. Both SDR Console and SDR Uno have buttons on their windows to suspend the synchronization and you can then tune to a different frequency to that to which the FTdx101 is tuned - possibly in a completely different band if your antenna routing will permit it. Again, this works perfectly well - until you want to restore the synchronization. The restoration is just a case of clicking the button on the screen of the SDR application again, but neither SDR Console nor SDR Uno give you any function to specify which device, the FTdx101 or the SDR application, should be considered the master. It is all a question of timing and cannot be reliably predicted - you have found an interesting signal on either the FTdx101 or the RSP1A and want to listen to it on the other device, but you could easily find the restored synchronization works in the opposite direction and you lose the frequency of interest.

In order to resolve this, 101Cats introduces a second interface to an external SDR application - the "SDR Port" that is referenced in the configuration screen. You create another virtual port pair, configure one side of that pair into the SDR Port of 101Cats and the other side into the CAT function of SDR Console or SDR Uno. Once you have done this, the two buttons “To SDR” and “From SDR” that appear on the right hand side of the main screen become active. If the synchronization has been turned off, then these buttons allow you to transfer the tuning in either direction in a controlled manner before re-enabling synchronization.

Note that there is a configuration setting which specifies which SDR application is being used. Currently, the only options are SDR Uno and SDR Console. This is a recent addition and not included in the configuration dialogue box - it is necessary to edit the configuration file manually in order to change it. See the pages in this Wiki for instructions on how to do this. The relevant configuration item is the "App" setting \:

Permissible values are SDRUNO and SDRCONSOLE.