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SmartSDR CAT & DAX - in depth

How well do you know DAX and CAT?

DAX is for sharing audio from the radio. CAT is for sharing frequency information from the radio. Did you know you can run DAX and CAT on multiple computers at the same time? You could have digital programs running on 2 different computers to the same radio at the same time. Some very cool stuff.

Video Transcript

This video’s full transcript has been provided below for your convenience.

Today I want to talk about SmartSDR and some of the basic interfacing that we do. By interfacing, I mean you’re allowing your logging program or any other program to communicate with the radio. There are a couple of ways to do that, but I’ll try to keep this fairly straightforward. The first time you start SmartSDR and you’ll notice it, by the way, that each of the icons have a version number on them, so that if you install a new version, you will have a new set of icons with new version numbers. So keep those in mind, if you upgrade to a different version or even downgrade to make sure you start the right version number. I tend to delete the ones off my desktop that I don’t require anymore. However, you can have many different versions on your computer without any risk of anything going right or wrong.

The software will ensure that the radio is updated and we call those upgrades and downgrades. They’re all okay. We do them all the time and there’s no risk to doing an upgrade on our radio or a downgrade. You always have a plan B that you can go back to a previous version. Couple things here on the SmartSDR main window. Now, we see two radios here. There are a remote radio. We have a 6500 in my local 6600M. You’ll notice that when I hover the most over the radio, it pops up with this little black box. Well, right now it doesn’t mean much, but if you have a licensing issue or a concern, we may ask you for the contents of that little black box, and we’ve made it fairly easy to deal with. Again, put your mouse over top. If you right click, it’ll say copy radio info clipboard and when you do that, you can then paste that into an email, which is pretty handy.

So, as an example here, if I just bring in a blank text document, and we’ve copied that to the clipboard and I write click and I hit paste, you’ll see that this showed me a lot of key information. It was actually the same thing. It’s all in the black box, but it’s also one of the items we start with immediately. And if you’re opening a support case, for any reason, it’s probably always a good reason to include this because it tells us a lot of items. So we’ll get rid of that. The other thing here in the chooser, you notice that I have a radio that says SmartLink. That’s a remote radio and I have this one that does not say SmartLink. That’s a local radio. It’s on my land and I can see it. It’s right here. I can touch it.

It’s right beside me, and the one above is about a hundred miles away. That’s what that is about. Look here at the settings before you go any further and we click on that, you have a choice. On startup, you can auto connect to the last radio. That’s probably what most of you like to do if you only have one radio, or auto connect via SmartLink. So that’s, that’s pretty handy. We’re going to start up my 6600 and we’ll show you a few things. Again, we want to talk about SmartSDR CAT here and SmartSDR DAX and they’ll be somewhere in your desktop. We’ll connect to my 6600M and up it pops and yes, I do a lot of six meter and two meter work. So in my case, SmartSDR DAX and CAT did not auto start.


I have it disabled. For most of you, it will automatically start and I’m going to open CAT and CAT is for the communications between the radio and your software programs. Just like any other radio you’ve had, where you’ve had signal links or CAT control devices. You don’t have to buy any hardware. We’ve got it here in software for you. So we want CAT to connect to this radio is the one I’m using. And again, don’t worry about the SmartLink stuff. That’s only if you’re doing a remote operating and we can can see CAT here and I’m going to move that over there. And we’re going to start DAX, and DAX started in a whole other window. I’ll just drag it over here, but you can see it here. We’ll come back to DAX in a moment. Let’s talk about CAT, and CAT’s the really critical one and what this is telling us, you’re going to see these windows here.

They say C, P, O, there’s a bunch of different ones, but for most of you, the important one will be C and probably P. So right now, this says we have a CAT port, CAT serial RS232, they’re all the same name. They mean the same thing. And they mean usually use them to control the frequency, the band, or the mode you’re on and few other settings.


The auto switch TX means that if the program, this might be WSJT or DM780 or some other digital program would like to talk, put the radio into transmit that it will automatically put the radio in transmit. I’m going to click on this 14 and let’s edit it. This is generally what it looks like. If the name is blank, you can put something there, but it is COM14.

This one is related to VFO Slice A and that’s VFO Slice A, which is… This A up here, it sort of hidden. Let’s move that out of the way. That A right there, we’re going to go back and edit this. You’ll see that it’s A, but look at the choices, because this is a four slice radio. I can have A, B, C, D. If it was a 6700, there’d be four more and if you were on a 63 or 6400, there would just be A and B. What this means is that this CAT port, this serial port, this RS232 port, all mean the same thing are going to send commands or listen to commands from logical slice VFO A up here in this case, it’s on six meters. So you can leave split mode alone and generally we want… I’ll drag that over so you can see the message that pops up. Generally want it to automatically switch, to push to talk to this device. We’re going to cancel that, because there’s nothing to save. Most other programs or most every program you have will also require for the radio to go into transmit.

Well, you can do that by sending a CAT command, which is a serial command over this port over COM14. And you can actually see those in device manager if you’re so inclined and they actually tell us part of a story as well. I’ll bring up my device manager and we’ll go down here and we see, we have ports and we open the ports and you’ll see, there’s a 14 right here. Now under the covers, and you don’t need to worry about it, it’s actually linked to COM114. Do not delete these. They’ll break your ports, but I’ll just leave these alone. We’ll come back to that because I’m going to show you what happens next. You can take a screenshot, but you’ll probably notice there’s a 14, but we don’t see a 15. Keep that in mind. So push to talk, I personally like to have a different port for push to talk, so we’re going to add a new port and we’ll pull that over here so it’s a bit more visible. And this port protocol now becomes push to talk.

That means that the software program, whether it’s DM780 or WSJT or something like that will use this serial port to exert or send the push to talk command to the radio. It’s two things you need to know when you’re setting up your other program. It’s going to be COM15 will be the port number you’re going to reference and you can’t have duplicate numbers. These ports have to be unique meaning you’ll have many of them, but they all mean something specific and then they all only do one thing. And it’s for VFO slice A, which is the same and RTS, which is a request to send. That’s an RS232 port number or designation. Don’t worry about it. It just does though remember needs to match the program we’re using. The unwritten convention is RTS is what we use. An active low means when the software, your logging program or WSJT or something like that, pulls that port line or that hardware line low or to zero volts, then the radio will go into transmit.

We’re going to add that and we’ll see that takes a second and up here, we’re going to have when it’s done, we’re going to have a COM port 15 show up right there. That means push to talk. And remember, now we’re bringing the device manager over and now you’re going to see, we have a COM15 and a COM115. Don’t worry about the hundreds, they’re required. They’re just there for information. That’s how the ports work. Let’s say, now I’m going to run… I want to be able to work on VFO B. Well, we’re going to need another CAT port. So we’re going to create CAT again. It’s going to be serial Flex VSP. Don’t bother changing this and we’re going to select B and hit save. It’s going to probably create me a 16, well shows me there, 16. And again, if we look over in device manager, you’re going to see we have a 16 and 116. They’re actually linked together. And again, guess what now? You want to push to talk, we’re going to add CAT, push to talk on B and hit save.


That’s how the COM port works. What’s really beautiful about this part or how FlexRadio did this is it allows you to have multiple programs accessing your radio CAT information at the same time. Now think about that for a minute. Any other radio there has as one, some have two, CAT ports that allow programs to access each at the same time, but the way we did it, we could have as many as we want. If I wanted to go back on A here and I’m going to remove, let’s say, I don’t want this anymore so let’s get rid of it. We’re going to remove it. Just to keep this clean, and we’re going to remove this CAT port as well, which is 16, just to keep it clean. If you’re watching device manager, while you’ll do this, you will see them disappear.

Let’s say I wanted another CAT port, because I’m going to use 14 and 15 here for WSJT. But I also wanted my logging program to talk directly to my radio and maybe that’s Ham Radio Deluxe. I’m going to add another CAT port on A, so I’m actually going to have two CAT ports talking to the same VFO, the same radio or the same slice. Now this allows us to have multiple programs using the same radio at the same time. If I repeat this and do this for push to talk, that’ll give you that option as well. You could do that again and again and again. If you think back, if had used some of the older programs like you had a RigExpert or a SignaLink or something as a CAT device in between, or maybe even the other vendors’ sort of escape me, you had to disconnect.

You had to close down one program, because you would have a what’s called a port contention because only one program can use a port at the same time. I’m running HRD, maybe I was running something like RTTY or PSK31 or N1MM for that matter. Yeah, I want to now just use my logging program because it’s my day to day stuff. I would have to close that down and then bring up my logging program so we could access the hardware USB port that we installed on the radio. That’s the big advantage of a FlexRadio and the way we communicate over a network is this allows us to have multiple use the radio all at the same time and you can make it as complicated, as simple as you like. It’s 100% totally up to you. So, that’s the CAT part.

Again, CAT computer data, I think it leaves configurated transceiver control and for push to talk and frequency and mode. There are some other protocols here. You can have OTRSP, which you would do if you were setting up a N1MM or a SO2R type station. You can have a wing here for CW keying. The setups the same, or you can have a TCP port if you’re setting up N1MM spots so that they show up on the waterfall. It’s a little beyond what I want to talk about right now, but they are there and they’re discussed in the manual. Okay. So, that’s CAT.


Let’s talk about DAX. DAX is used to send audio from the radio to your program. Let’s focus on maybe WSJT but any digital sound card program, Fldigi 2Tone, MMTTY all behave exactly the same way and the setup is identical. For the most part, you have three things to worry about/ the audio coming in, the audio, going out for the transmitter, and putting the radio in push to talk as well. Maybe I guess that’s four things. You also have CAT control. So in DAX audio, if we happen to look here, we see that in WSJT this is, if you’ve used it, you’ll see that we have a new input. This is the audio coming into the radio, the DAXs audio from RX one. And that relates to this DAX control screen called RX one.

I’m going to I’ll drag this over a bit so the popup is visible and it says, it’s coming from my radio at this IP address, the channel’s enabled and the streaming rate, we’re moving almost 400 kilobits, a second fair bit of audio. That’s going right into the WJST program. But what is key is that for VFO slice A that we have DAX, this RX one, and this one are the same thing in a path.


If we had another copy of WJST running or some other audio program say it’s Fldigi, we might use RX two, meaning that it’s coming from the second VFO. So let’s talk about that a little bit in a minute. This key is that this one for most operators, until you get a little carried away and want to do more things with all you really need If we’re doing one thing at a time.

In the TX audio, the TX streaming, the output, this is the output from the software program to the radio goes here and then over to the radio. There is only one TX port and you use the same one for all programs because only one program can use it at a time. From a WSJT perspective, that’s what we want to look at. That’s part one. When you’re in a digital operating mode, we are generally in DigiU for upper side bend, generally. I’m sure there’s a few exceptions. You’ll do want to make sure that your bandwidth is about three kilohertz, or you can go as high as six. That’s how wide the receivers are hearing for WJST. The reason we want to use U is that in this format, there is no EQ or emphasis or anything between the programs and the radio. It’s all, as we call, flat. You don’t have to worry about hot spots or sweet spots in the band pass filters that you do with analog radios. Makes that work fairly well. If you’re going in to digital modes, you do have to have three buttons clicked or checked.

Let’s start on the receiving stream, the RX stream, and we’re going to focus on one. Then we walk over here and you’ll see it’s DigiU. The DSP you’ll leave alone. This DAX is key. This has to be channel one. That channel one is this channel one. You’ll see if I drop it open there’s four, and that’s, we can have four receivers, but generally one and one. You’ll notice on my second split down here that my DAX is on two because that goes to a different copy of WJST, but let’s not get too far ahead of ourselves. I’ll leave that as two. And if we open up the control box and I hit the little angel you’re at the bottom, you also need this in DigiU to be set to DAX so that the audio coming into the radio being transmitted, you’ll see it says DAX is primary transmit audio source, is where we want to go. You’ll notice that the processors turned off and because we do not want in the audio processing, we’re probably going to leave this as normal here and not with…

Actually, you can’t even change it in DigiU which is correct. That’s how that part of DAX works in what we call the analog world. Down at the bottom, these are for special programs like usually CW Skimmer, et cetera. For the most part, you can leave it alone and leave it turned off. If I wanted to assign this to a pan adapter, say the second one, it’s actually I think in display… No, right here, actually in DAX of course and I would say channel two. You’ll notice when I did that it says now 144.174, and it’s the sampling rate. Again, that’s more of an advanced feature so don’t worry about that. We’ll leave them turned off.

You can adjust the levels, inbound and outbound to your programs with these sliders and your transmitter gain here to drive the radio from the program. I would make sure I don’t have a set up to transmit. So I apologize, but this level meter will show you the audio level going into the radio while you’re in transmitting from your digital program. You want to make sure you keep the peak of that below zero, somewhere about here, minus three, minus five and that’ll keep everybody really happy.

In CAT by looking in the manual and the manual is quite good. You can download it from our website, go to, look under support and then downloads and it’s in a couple of places. We’ve got a great search tool here for finding pretty much everything, but for version three here and then documentation, and there’s the user guide. If you click on it, it will download. I will bring a copy of it over here. So you can see it. It’s a very healthy manual. It’s written by HAMs for HAMs. It’s written in English and it’s got pictures in it. You’ll see here on section eight of the initial setup of CAT and DAX. You’ll see the initial setup for DAX and hopefully with a combination of my video and some pictures here and some stuff that those that have used it have written up, you will find some more instruction on DAX and CAT and that will help you out a bit. We then go into section nine, which of course is SmartLink, and that is only required if you’re doing any sort of remote operation.

So that’s it for now, any questions how to reach us. If you have any support issues, please open a support ticket. You can also do that on our website and the guys will be happy to help you out. I want you to have a wonderful day, great DX, and that is a SmartSDR CAT and SmartSDR DAX.

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