The Awesomeness That Is The Signalink USB Sound Card Interface

Anyone that has been following my Twitter will already know that I’ve just become active on WSPR.  As of now, there are just 3 people following my Twitter – my brother Simon, who as far as I know, isn’t interested in amateur radio at all (and probably didn’t realize that my Twitter is strictly amateur radio related when he signed on to follow me, so is probably wondering why I’m such a geek who speaks only in jargonese),  some company called “Memory Suppliers” (why are they following me?), and my friend Antoinette.  Antoinette is my biggest hope here, as she actually bought the Radio Amateur’s License Manual at HRO a few weeks ago and has declared an interest in getting a license, so I’ll keep my fingers crossed that she pursues it.

A couple of weeks ago, I found a blog by Jason, NT7S.  Jason is a Buddipole employee and an electronics and radio nut with a strong passion for electronics and radio.  (What is it about these politically correct phrases that look as if they just popped out of a boring resume?  I’d much rather be described as a radio nut than as someone with a “strong passion for radio.”  It’s the anti-corporate side of me coming out.  I don’t know Jason personally, but I think he’d understand.)  One of his blog entries discussed a mode that was new to me – WSPR,  and my interest was piqued.  Check out Jason’s blog when you have time.  It is written from the perspective of someone who has a strong technical background, but he has a personable manner that makes you feel as if you’re on the same journey as him.

Back to WSPR. If you’re a radio amateur (and I’m hoping that before long I can persuade a few hams to sign up for this blog),  and you have any kind of interest in the propagation of radio waves, WSPR may well be of interest to you.  Have you ever worked on an antenna and wondered how it’s getting out, but felt that you’ve asked your ham friends for signal reports one too many times? Perhaps you just want to see how your signal gets out but don’t feel like getting into a long-ish QSO just to see if your signal is being received in South Dakota. I’ve had some really memorable contacts, including the one with XE2IZN in Oaxaca, Mexico who was living in a remote, fertile valley with the indians.  They didn’t have easy contact with the world outside their community, so to hear his voice from his battery-powered 10 watt signal, to talk with him, then to listen as his signal faded into the noise was magical.

Let’s face it though, not all QSO’s are this memorable.  Sometimes you make connections with people, and other times you just don’t feel like swapping details of rigs, linears, QTH’s, and fascinating information about whether it’s raining or cloudy at each end with some guy called Bert whom you might never talk to again. Many apologies to anyone called Bert; it’s a fine name, but you get my point.

This is where WSPR comes in.  Your computer makes semi-automatic beacon-like transmissions.  They are heard by other stations, and your computer hears their transmissions also.  The transmissions include data on location, transmitter power and received signal strength, amongst other things, and all this data is automatically uploaded to a website where you can look at it.  There’s even a map of the world showing which stations are hearing which other stations.  Brilliant!

WSPR was written by Joe Taylor, K1JT, who also wrote the various protocols of WSJT, digital modes that allow for two-way QSO’s at very low signal levels.  They can be used for weak signal work on the VHF/UHF and HF bands, including EME (earth-moon-earth) and meteor scatter contacts. WSPR is also a weak signal mode.  My copy of the program regularly decodes signals down to 27dB below noise level; I hear that it can produce decodes down to 30dB. If you listen to a signal that weak on the speaker of your radio, you won’t hear anything – it’s amazing that the program can produce intelligent information from what to you just sounds like band noise!

I downloaded WSPR, plugged the line level audio output from the data port of my radio directly into an input on my sound card (not a great idea), set the radio to the frequency recommended by the program (the most popular frequency is a dial frequency of 10.1387 USB in the 30 meter band) and began receiving transmissions from WSPR stations almost immediately.  Some of the stronger signals you can hear – they sound like pure sine wave tones, though they do vary in pitch by up to 6Hz.

But it wasn’t enough to be receiving signals from 0.5,  1,  2 and 5 watt stations around the world; I wanted to be one of those stations too. If I were an impetuous lad, I could have jammed the output of my computer’s soundcard into the mic input of my FT-817 in a bid to get on the WSPR airwaves.  It might have worked, but it might also have fried something. If you want to connect your radio to a computer sound card in order to set it up for digital modes, it’s recommended that you isolate both the audio outputs and inputs of your transceiver.  What you need is an interface that will accomplish this, as well as keying the PTT line (the thing that tells your radio when to transmit and when to receive.) There are many simple circuits online that will do this – a google search will find them.  There’s even a neat one for the FT-817 by KK7UQ that can be built into an Altoids tin.  (Good grief, has anything NOT been built into an Altoids tin?)

I don’t have a good stock of parts at home, so a decision to build an interface would most likely have resulted in my buying the parts from multiple sources.  That, and the fact that I wanted this thing soon led me to the Signalink USB manufactured by Tigertronics. They make an interface for around $70 that interfaces your radio to your computer soundcard. However, for just $99, they make an interface with it’s own sound card, AND it comes with all the necessary cables. DEAL!

The advantage of having the interface with it’s own internal sound card is that you can leave the Signalink USB, computer and your radio to happily transmit and upload away, and if you want to listen to something else on your computer on the computer’s sound card, you can, and it won’t interfere with the radio transmission.  So if you want to make WSPR transmissions and check out the video of Michael Jackson’s ghost at Neverland Ranch at the same time, you can.  (No, I’m not going to provide a link for that, but it does exist.)

The Signalink USB interface is like manna from heaven.  It is pure awesomeness in a little case measuring about 4″ x 3.25″ x 1.5″ (the 4″ includes the height of the knobs.) Fit and finish are very nice and it works well.  It comes with a cable to connect to your radio (you specify which cable you need), and a USB cable to connect the interface to your computer.  That’s it.  There is no power cord – it gets it’s power from the USB cable.

Because there are so many different radios with different wiring configurations, you have to set a few internal jumpers so that the data cable will work with your particular radio.  It is recommended that you set the circuit board on a book or similiar non-conductive raised surface, so that you can perform this procedure with the front panel still attached and not damage anything. Slightly to the right of center, you can see the IC socket that is used for the jumpers:

Looking down on the Signalink USB circuit board from above, with a copy of "Walking In Britain" as a protective base.

The first 2 jumpers have been installed.  See how sitting the circuit board on a book or other raised protective surface will prevent damage to the circuit board and front panel assembly when you press down on the socket to insert the jumpers:

The board with 2 of the jumpers inserted.Here's the board after the insertion of 2 of the jumpers:

All jumpers have been installed, and the board and front panel assembly are slid back into the case:

The board fits neatly into the rails on the inside of the case.

And here’s the Signalink USB sitting on top of my FT-817 and Z11 Tuner, for size comparison:

The Signalink USB sitting on top of the FT-817 and LDG Z11 for size comparison.

I have a tendency to strap things together with velcro. These are cow ankle straps that I bought from a supply company based in Wisconsin (lots of cows there!)

I started this just so that I could participate in WSPR, but I now also have a station that can handle PSK-31, Olivia, Throb, Hell, Thor, DominoEX (hey, hang on, I swear there’s a good band name in there somewhere) and pretty much any sound card based digital mode I can throw at it.  All for $99 – and I got to chat with Alex at Tigertronics too, who will be happy to extoll the virutes of Grants Pass, Oregon, and how it compares to Southern California, if you can tear her away from helping the other Tigertronics’ customers. She’s very helpful.

If I haven’t already made this clear, the Signalink USB is a well made piece of kit that will make you feel happy you own it. It’s also small, so if you own a laptop, you just might consider working digital modes on trips away from home too.

On the first night of operation, my little 0.5 watt signal was copied as far away as Hawaii and Japan, as well as in many places all over the US.  WSPR is an interesting mode. Thanks Jason.

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