This is going to be long and detailed, so brace yourself. This is a pain but you only do it once (ahem!) and the Flex is brilliant once set up. Other SDR rigs will be similar.
With a traditional non-SDR rig like an FT-817 you would use two types of real lead, a
PTT (or CAT) lead, usually from a USB socket on your computer, and an
audio lead plugged into an audio card.
You would have to buy these leads. With the Flex and other SDR rigs you can do all the connecting together inside the computer. Instead of connecting a computer to a rig with real leads, you are connecting one piece of software (your data program) to a different piece of software (the Flex operating system) and passing the data inside the computer.
Just to warn you at the start, I use "Control Panel" on my PC set to display "Small Icons". By default it is set to "Category". You had better change yours to small icons or a lot of the navigation within Windows will not make sense. You can do it by Category, but it is very fiddly. It is fiddly enough already.
The Flex 1500 is a well known route for many people into Software Defined Radio (SDR). It is a 5 watt output transceiver, small, with just one control on the box, an on/off switch. Everything else is controlled via the computer it needs to drive it.
The idea is simple enough. It covers general coverage receive from 490kHz to 54MHz and transmits in all amateur bands in that range. If you buy the rig it comes with a version of "Power SDR" software to drive it. As supplied the transmit frequencies are limited to amateur bands in your area, and you need to get the rig "turfed" if you want to transmit in other areas or if a new band is authorised in your area.
I have had mine for over 4 years now (now is April 2015). I bought it initially to use it as a transverter driver. It is well suited to this as it has 1mW (0dBm) output sockets at the back, plus the ability to use separate receiver sockets and configurations which mean that your frequency in the PowerSDR screen is correct for your transverter. I used it this way with three or four different transverters before I started using rigs designed for the bands involved. Since then my Flex is used mostly for 6 metres, or sometimes 10 and 12 metres - almost always on data modes.
The Flex has done me well and I have used it frequently. In fact, it is now one of the longer-lived pieces of equipment in the shack. You would have to say that it has a brilliant receiver in that it has the SDR ability to use a wide range of filters, plus the computer controlled ability to move around the band using the fantastic SDR software.
The Flex 1500 has two receivers, and I have used both to receive WSPR and JT65 at the same time on 10 metres, though you can only transmit on one. Fine, but they both need to be within the display range.
That screenshot of PowerSDR above also shows a problem, a second "image". The second signal below (to the left of) 70.200 is in fact an "image" and is not really a second station. All superhet rigs have images, it is just that you usually cannot see them. Often they fall outside your range of use. They are usually going at some multiple of the tuning rate in the wrong direction. I have never actually replied to an image (they are usually reversed sideband so do not work in data, but they could fool you in CW). They stick out a mile. However, they are an issue with the Flex.
OK, so on to data modes (at last you say!).
With the modes I use, I set up the PowerSDR to work the push to talk ("PTT") and inject an audio tone into the rig. It is just like using cables to connect a computer to a standard rig, but all the cables are virtual and inside the computer. There are four cables I use in total, two serial cables for the PTT with a numbered port at each end, and two audio cables with sound inputs and outputs at each end.
You can set PowerSDR up in memory so that if you click a memory setting like "6m WSPR" the rig will go to the right frequency, select the right mode (DIGU), correct filter, and switch from microphone input to "VAC" (more about VAC later). Then if you click something you have saved at "6m SSB" all that can be reversed at one click of the button - magic. But the memory does not recall the audio settings, which you have to change separately. for example, I need much more rx drive for FSK441 than I do for WSPR. Still, the audio has memories too, so I set those up for "WSPR" or "SSB" and that makes just two clicks to make.
That audio settings problem would be solved, incidentally, if all WSJT programmes had variable audio input and output like WSJT-X. But on WSJT10 you can vary the input level but not the output, and on WSPR2.11 you can vary the output but not the input. I know that there are plans to bring the all together, but that will take time.
So, to connect the Flex 1500 to a data program like WSPR or Ham Radio Deluxe (HRD) you need to cover the two aspects. One is the PTT and CAT line (2 virtual serial cables) and the other is the audio line (2 different virtual audio cables).
For PTT you can connect to PowerSDR either by CAT or simple PTT. PowerSDR accepts either and I always set up both. Some data programs, like WSJT10, do not have CAT. Others like HRD are best used via CAT. So it is easier to set up both though you only need one at a time.
As both WSJT10 (our current example), and the PowerSDR software, are on the same computer, you will use "virtual serial ports" (VSP) connected by a virtual cable for CAT and PTT. Thus when WSJT "presses the PTT", the PTT signal goes by digital connection to PowerSDR and tell it to pess the TX button.
The VSP I use is "VSP Manager" by Steve Nance (K5FR). You can get it from him at k5fr.com. At the time of updating this link (09 Jan 2016), it works if you click HERE. I will do my best to keep the links up to date but if this does not work you may need to contact K5FR directly.
Quite reasonably K5FR asks you to let him know you are using it. He says this:-
If you are an Amateur Radio Operator and would like to use VSP Manager for your *Personal* use, contact me with your call letters and I'll be happy to send you a copy.
If you're not a licensed Amateur Radio Operator don't bother to apply. There are no exceptions to this rule.
It is free and he is letting us use it, so fair enough. An SWL does not need it of course. They can skip directly to the audio connections, lucky people.
You simply download, install, and set up VSP Manager. It asks you to select a pair of ports which are connected by a virtual cable. I install two pairs, one for CAT and one for PTT. This allows non-CAT programs like WSJT10 to point to one, and CAT programs like HRD to point to the other.
So I set up pairs of Virtual Serial Ports at each end of the cable. I call one pair 6 and 16, and the other 8 and 18. Don't ask why, that was suggested by an article on the Flex site. Keeping one number of the pair below 10 is a good plan as some programs are fussy about that, and the other is just 10 above for convenience.
Make sure that 6 and 8 (and their pairs16 and 18) are not already used on your computer. It isn't very likely but you can check in vspManager as shown above. If they were in use, they would be listed under "Physical Ports". When you plug in something controlled via a USB socket, Windows will give it a number for the next highest port it thinks is free. If you find that 6 and 8 are already allocated by Windows, go to "Start", "Control Panel", "Device Manager", pick the "Ports" tab, find your ports and any that use 6 or 8, select them, go to into "Port Settings" then "Advanced" and simply change the number away from 6 or 8 (or 16 and 18).
Even after you have chosen to use 6 and 8, Windows can sometimes allocate the number to something else you plug in for the first time, so it is something to keep an eye on.
VSPManager has a habit of telling you that it has failed to create the ports, but just continue to set them up and they will work, at least you might have to reboot the PC first (it has to be a PC, the PowerSDR/ Flex combination doesn't like anything else but apparently it will run in Wine).
OK, you are ready to go setting up PTT with the VSP. We will deal with CAT later. Connect the PTT program (e.g. WSJT10 in this case) to com port 6. That is one end of the imaginary cable. In WSJT10 it is called "PTT port" and you have to enter the number directly.
Connect COM 16 into the PTT control by using the drop down menu and selecting port 16.Then click "enable PTT" before you select enable CAT. YOU HAVE TO DO PTT FIRST, SELECT IT, AND THEN DO CAT SECOND - if you need CAT too. Even though this photo shows both connected, you cannot set CAT first and PTT second.
OK, for CAT type programs, I suggest you follow the above first as you never know when PTT might be useful. Then you select port 8 in your program (in this case WSJT-X as in the photo below). Note that the PTT is set as well as the CAT, and WSJT-X will work in this mode but if you change band the rig will not change automatically with you unless you have CAT selected, nor will the +2khz button work without CAT).
Note too that the Flex emulates a Kenwood TS-2000 by default. You can chose other settings, but those work fine for me.
If you are using something like WSJT-X you can test the PTT and the CAT using buttons on the setup screen.
OK, that is the PTT and CAT sorted out. What about the audio?
Just like PTT, you can keep the audio connections inside the PC. You CAN use real live audio cables just like you would with an FT-817 or whatever, in that case two audio cards in your PC and an audio cable between them. I have done it! It works! However, it is very lossy, getting the levels right is a pain and I would not recommend it. Keeping it inside the PC using virtual cables is much better.
What you need here is a virtual audio cable (VAC). You can buy one from Russia. It works and my credit card was not ripped-off. However, I found the Russian ones hard to set up and given to breaks in service. So I recommend VB Cables which you can find HERE. These are freeware - I donated a few Euros and they sent me a very nice email thanking me for the money.
No big deal with the VB cables. Once again you have to imagine a cable. A virtual audio device (which will appear in your list of sound devices just like a headphone socket) will accept a digital audio signal from a data program, pass it down an imaginary cable, and the signal will appear at the other end from an other virtual audio device..
VB Cable send you three, which appear in Windows as "VB Cable" "VB Cable A" and "VB Cable B". Each end of each cable shows up as in input and an output device in you list of sound devices in Control Panel. You install them on your PC, but it is best to right click on them and use "Install as Administrator". Then you plug one into your program for input and one for output. At the data program end I always use A for input, in case I get confused (!). You can see them in the WSJT-X photo above.
The other end of the cables goes into the PowerSDR by following "Setup" then "Audio" then "VAC1".
This is much the same procedure for other SDRs and other data programs. HRD is a bit odd as it allows you to use basically a rig control system (HRD itself) to piggy back a data program (DM780). That works fine but it can introduce even more latency, rate changes and so forth. I have been able to run DM780 independently of HRD and drive the Flex direct, which reduces the latency a lot, but it uses PTT control so there is no CAT. Maybe since I resolved the 48000 Hz rate issue with VB Cable this will no longer be necessary. We shall see.
Anyway, there you are. What a palaver! Still you only have to do it once (I must have done it dozens of times after re-installing Windows etc). However, once done it works very well indeed.
P.S. Thanks to countless people for coming up with the ideas set out here, especially on the Flex and WSPRnet sites.