Understanding
Soundcard Interfacing
by Ernie Mills, WM2U. http://www.qsl.net/wm2u

Please print this article and use it as a hand out at Club talks and lectures
Interface (Russian) tnx to Andrey Otroshenko, RA3DOA

This page is an attempt to correlate the interfacing schemes for various Radio models, and Sound Card configurations. Since 26th December 1998, when the sound card version of PSK31 was first introduced to the Ham community, and after much dialog, experimentation and confusion, an interfacing pattern slowly emerged. I feel that an understanding of this pattern is valuable and can save you a lot of time and grief. Please note that each circuit references various letters which will correlate with the Radio pin-outs on the various popup tables available. Just click the manufactures button below, pick your radio and read off the hook-up points.

I Urgently need other Radio hook-up info. and corrections.  Please submit this Form for it's inclusion onto this page.

You have a Kenwood Radio and your hookup information is not here! Don't panic! Goto the Kenwood. Amateur Radio site, then to the "Jump To" pull down menu and... hey presto!  If it is not on this list, it was never made.

If you can't find it here try this great TNC to Radio page; Hook-Up Magic

Ok! Ok! so you prefer to buy (that's a dirty three letter word) a ready made Computer to Radio Interface. Check out this nice package by N1ZZ and K1UHF. They call it the RIGblaster

Wait!!! are you hooking up a fully computer controlled Radio? One with a virtual consol? The Kachina, Pegasus or whatever? Hey! first read George's Notes

STOP!!! If you are a FT1000MP owner, look no further. Doug McCann, VA3CR has a web page dedicated solely to that fine machine. This great site is a one stop information authority and missing it will be your loss. You are warned :) Check out http://www.va3cr.net/.

Thomas Giella, KN4LF, has also a great web site showing hookup information for the FT1000MP Mk5.  Check it out at ~ http://www.kn4lf.com/kn4lf10.htm
Ok, Almost there, but before we get into it, please read this email I received off Jack, K8PET if you are thinking of interfacing to a LapTop computer.

First off, keep it as simple as you can. This circuit shows a single connection between the Radio Audio Output and The Sound card LINE IN, and a simple 100:1 attenuated connection between the Radio Aux. Mic IN and the Sound Card LINE OUT.
For SWL the fastest way to Rx is to simply let your Computer listen to the Radio. If you have a microphone connected to your pc, load your PSK software, and tune your rig to a PSK signal and tah-dah, PSK print on you pc screen. :)

The most simple Sound Card hook-up. Use this first. If system works OK with no ground loops then stop right here. Your finished!
Oh! before we start a little word on the component abbreviation used on these diagrams. Since the decimal point was not showing up too well in cases like 4.7k ohm I adopted the European system which uses the 'k' as the decimal point. So the 4.7k ohm now will be marked as 4k7 ohm.
The 100:1 divider is very important because the output from the Sound Card can be in the order of 1volt into the microphone input which is nominally 10mvolt. It follows therefore that without the attenuator, microphone input overload can result, causing the normal narrow bandwidth to increase dramatically producing unwanted splatter.

Try this hook-up first. If you are operating clean and you are having no ground loop problems, that's it. Read no further. Your done! There are a lot of Hams who operate very well using just this circuit.
So! you have ground loop problems eh? Well the next step is to isolate your sound card from the radio. To achieve this, check out this well proven schematic shown at right.
W
ith this configuration the VOX is used to trigger the PTT line for Transmission.

OK, with a bit of luck all is ok now. If not you must add isolation on your PTT and/or CW line. Carry on!
Talking about VOX, I received an email off Mike Waters, W0BTU. It is well worth reading giving the virtues of VOX over PTT see http://www.w0btu.com/digital_modes.html

After believing that Radio Shack does not handle these transformer it turns turns out that they do. Radio Shack does have transformers available. Many thanks to Steve, KB0OLF for this information. The Radio Shack stock number 273-1374 is a 1:1 transformer with an impedance of 600-900 ohms, designated T2 in our schematics, and the 273-1380 has an input impedance of 1K ohms and output of 8ohms, T1 in the schematics.
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nother source is Bux Comm at Warehouse 209;  Office 211;  Luenburg Drive; Evington,  VA 24550;  FAX 434 525 7818 or email Buck at k4abt@packetradio.com and tell him I sent ya! ... yea! he'll charge you double. :)   Take a look at Buck's web page for these items at http://www.buxcommco.com/
A
nd while we are on the subject of transformer availability, I received this great tip off Peter Jackson, G3KNU who reports that, "
I have found that transformers off telephone modem cards work FB, there are plenty of them at rallies now that lots of folk are going broadband. I picked some cards up for 20p".  Hey! it doesn't get any cheaper than that folks!  Thanks for the tip Peter.

Now, a very simple transistor circuit can be added to automatically switch the PTT circuit on the Rig. This uses the RTS line in the active Comm. Port. The voltage swing on this is -12v/-5v through +12v/+5v so this line is always 'hot'.  To isolate the RTS line from other devices being used on the same Comm. Port, you might need to incorporate a switch.
I
mportant: Please check that the PTT line, and/or the Keying line on your rig has a positive voltage on it and it requires a pull-down to ground to activate. These circuits will not work otherwise.
What does that mean? Well, you don't need to use a separate Comm. Port just for this application. I have a Kantronics KAM (all mode TNC) connected to Comm. Port 1 and use the same Port for my sound card modes. The KAM is switched off during sound card mode operation.
Instead of using the VOX to operate the PTT line, this circuit will automatically switch over by using the Comm Port RTS line.

I take off the RTS, DTR and GND lines from the Comm. Port at the RS232 connector going into the back of the KAM. Since the KAM will drag the DTR line down, leave it disconnected at the KAM connector. The KAM does not use it anyway! 

Since you might already have used the RTS line you can use the DTR line for other switching chores. Very handy for sending Morse Code.

Ok! Included on this web site is a really nice keyboard CW program. I like the idea of being able to simply click an Icon and start operating one of a growing number of Sound Card modes now available. So CwType uses the Comm. Port DTR line to send Morse Code.

So! you have realized that with the inclusion of the TTL circuits shown above that you now don't have 100% Radio to Computer isolation.

Even worse maybe you  still have a ground loop problem. Well simply substitute one or both of these schematics for there equivalent TTL version. They are the same as the two TTL circuits above except that they use an Opto Isolator to switch the circuit.
The Opto Isolator is a 4N25, 4N29, ECG 3084, PS2601 or equivalent from Digi-Key, Newark or Radio Shack, I used a TIL111.
Uhmm! Just received this really helpful email off Kevin, AC0EQ. "You can get Opto-Isolator free samples from Fairchild Semiconductors by clicking HERE."

If you still have some ground loop affects after using the 'isolated' circuit above, then this Opto Coupled PTT line switch offers complete system ground isolation

To maintain 'complete ground isolation' you should use this circuit if you are using the DTR line for auxilliary switching.

An e-mail off Ken, W7LAR gives us a great tip by the way. If you want to get the Optoisolator from Radio Shack it will probably not be a store stocked item. You can get it direct mailed to your home by asking the shop clerk to order it for you from there warehouse. It is number 11305190 and costs about $3.00
Bill Strong also added that he also had problems getting Radio Shack parts but suggested going to a company called Mouser. "They advocate a call for non listed values and odd parts, 800-346-6873 Ordering can be done via Email or Phone. The On Line catalog list all. www.mouser.com"  Thanks for the info Bill.
Now, for you guys who have negative keying on those older rigs. This problem is not as straightforward as it first appeared. An email off Bob, W2SR pretty well sums it up.--
Using a classic rig like those made by Drake, Collins and Heathkit present a problem. Just how do you key a transmitter that has -30 to -90 volts on the keying line? Not with your average 2N2222 or 4N33!  So I looked into it and I will not try and reproduce the schematics here but will point ya! in the right direction. The first, known as the Jackson Harbor Approach, uses a high voltage transistor, MJE350. Unfortunately this kit is no longer available however if you go to http://jacksonharbor.home.att.net/keyall.htm you will find that Chuck Olsen, WB9KZY has designed a replacement called, The Keyall. He tells me it can key grid block (negative), cathode (high positive) and regular 13.8V solid state rigs - it can even key the Tuna Tin 2 transmitter - it's a solid state relay circuit. Thanks Chuck for this excellent kit.
Also checkout Radio Adventures who have a Grid-Block Adapter that is good to -200v see http://www.radioadv.com/ham_radio_equipment/accessories/bk170.htmArt Boyars, K3KU has a great circuit for keying both +ve and -ve keying voltages. This appears in the April 1993 QST magazine, and originally in the (PVRC) Potomac Valley Radio Club Bulletin, Feb 1990.  Other sources include-  J.Garrett, The WB4VVF Accu-Keyer in QST Aug 1973.  and D.Foster, Negative High Voltage Keying Circuit, Technical Correspondence, QST Jun 1991.

I must thank Walt Hoskins, W0EDS, for his recent enquiry asking how to interface the old Drake TR-4C. He wanted to run TruTTY software for CW using his sound card. We produced the circuit at the right. The diode is a 1N34 and the Dip relay is a 5/6 volt SPST, NO type from Mouser. #655-JWD-107-5
I recommend buying a socket for the Dip relay as direct soldering onto the chip is bad practice, and makes maintenance easier.
The drawing shows the pin out for this relay and the internal connections.

Well I hope this little reference helps ya! I was getting quite a bit of email on this :)

The following data was researched by  Henry, KC9TWY   ~   All you IC-7200 users take note.  ~
I just bought a IC-7200 and got a rigblaster plug&play with it as well. Wanted to share a few experiences that others may be struggling with.  (Come on, the real reason is that there's a real sense of achievement getting this to work and we want to brag).
Well, ends up, the new IC-7200 has a USB interface that works both as PTT and sound card so, theoretically, I shouldn't' have bought the interface at all.
I'm a hardcore Linux fan but use Windows eventually for testing and when some fancy games come out (watch for Battlefield 3).
I used the IC-7200 with both Rigblaster (will call it mode 1) and pure USB (call it mode 2).
Both modes - pure USB and pnp+soundcard - work great on both windows vista and linux (with hamlib). 
Big perhaps is that the USB is both convenient and easier to set up but it is not activated automatically when USB is used - as one would expect - so some tweaking is needed.
Here's an excerpt of my notes:
>>>>> Mode 1) Using soundcard: PC soundcard LIGHT BLUE (LINE IN) to BLUE on rigblaster (better than to connect it to the PINK/MIC) PC USB to rigblaster USB cable Rigblaster cable to IC 13 DIM Adaptor (sold separately) IC 13-DIM adaptor to ICOM 7200  ACC connector Set PC soundcard volume to 100% IC-7200:  - Quick set DATA OFF
>>>>> Mode 2) Using USB PC USB to ICOM 7200 USB  IC-7200: - Quick set DATA ON
For BOTH modes, set also this on the IC-7200: - SET/SET MOD M/A  <== this will be used when the SOUNDCARD is selected (mode 1) - SET/SET D-MOD U  <== this will be used when the USB is selected (mode 2) - SET/SET USB LEVEL 85 
The last set of options were pretty hard to figure out alone - as this is my 1st rig anyway. The default USB level 50 just does not seem to work on Linux for some reason. 
QUICK SET means pushing the SET button ONCE for 1 sec. There are 3 quicksets there. SET/SET means pushing the SET button TWICE for 1 sec. This gives access to a plethora of options.
For now I'm pretty happy with the USB (mode 2) option. It's very convenient. 
One difference between the two though is that the soundcard option allows 192,000 Hz sampling from the PC while the IC-7200 USB will only allow up to 48,000 Hz. This may make a difference for some hardcore DSP programmers/hackers out there, especially dealing with PSK. 
BTW just got my license and my 1st QSO (DX!) with someone 9,000 km away with my poor man's G5RV hanging out of my window to a tree nearby. The guy must have one of those 2km antennas we only see on pictures.
Probably keeping the rigblaster for some future use as it seems to be a great card anyway.
73's
KC9TWY - Henry ~~~ great piece Henry, Keep up the great work, Ernie wm2u  ~~~

Now for the Collins lovers and operators.

Many thanks to Roland Burgan, KB8XI  who recently sent me this interface he designed specifically for the Collins KWM-2. He does add however that it should work an any earlier rig.
Roland is well know in Amateur circles and has worked with FAR Circuits back in the 90's, for 73 Amateur Radio, Today Magazine. Remember the following articles? January/1995...Easy PTT Control; and August/1996...Receiver RF Preamp; May/1997...Build an Audio Multiplexer for Your Frequency Counter.
If you need further help or information on this please email Roland at rburgan@up.net
All parts can be purchased from Mouser Electronics;
T1,T2 .... part number 42TL016
K1 .....  part number 655-JWD-107-5 (DIP 5/6 VDC SPST-NO)
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printed circuit board can be bought from FAR Circuits. Take a look at the component list for contact details.
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or a complete list of components, click here. If you would like a printout of this list, simply right click on the popup margin and click print.

Soundcard Interface - Alinco Handheld DJ-580T

Finally for you Handheld Junkies, Greg Speakman, VA3OMP is sharing his well thought out modifications and designs for interfacing this radio.  ... follows an extract from his email ...
 ... I was able to connect the 3.5mm (⅛") ext speaker jack, on top of the handheld, directly into the line-in 3.5 mm jack of the computer's on-board sound card.  For the handheld's combo mic & PTT 2.5mm (1/16") jack, located on top of the unit, I modified your circuit with the Opto Isolator.  Diagram at left shows the mods.
Regards   Greg Speakman   va3omp@rac.ca 

Many thanks Greg for this fb addition to pc-rig interfacing.

 
WM2U Tip!!
I periodically get e-mail telling me that certain parts are no longer available from Radio Shack. I suggest therefore that you go to the Bux CommCo  Catalog where you get one stop shopping for all your component needs including the hard to get connectors. Oh! by the way Buck sells the sound card, ISO-KIT and Little Rascal. Hey! for about $25 you get all the components you need. You can't buy them yourself for that price! Check out the ISO-KIT info here. After reading Bucks' page, go to his Kwik-Select guide
The N9ART Interface
designed by Jim Mitrenga
Well! you are now really biting at the bit and want to jump right in there, build a new sound card interface, download that fancy new windows software and join the Digital Revolution. Hold it! hang loose a minute. Are you one of those Hams that uses a non-soundcard, serial port type, interface, and you are really comfortable with that DOS software? You are! well  join the crowd.... but you have realized that there is a problem. Yep! you will get tired of switching cables from one system to another.
Uhmm! well, I think we have the answer to that for ya!. Lets take a look at Jim's interface. This interface will give you the best of both worlds. You can certainly join in the soundcard Digital Revolution and guarantee clean signals but at the click of a switch you cut the the sound card out and fetch in the serial port interface that feels and acts just the way you remember. 
Check out the circuit diagram below. err! look familiar? It should. This interface is from an article that appeared in the November issue of QST, entitled "A Flexible Digital-Mode Interface" and is reproduced by kind permission of the author, Jim Mitrenga, N9ART.

A Flexible Digital-Mode Interface as presented in November QST 2000, by Jim Mitrenga, N9ART

 

The PCB photo of the Digital-Mode Interface

For a complete list of components, click here. If you would like a printout of this list, simply right click on the popup margin and click print.
Ok! the construction of this interface although somewhat more complex than the standard isolated interface, is nonetheless well within the capabilities of most Hams. All the components can be found at Radio Shack and a ready made PC Board is offered by FAR Circuits at http://www.cl.ais.net/farcir/ for only $6.00. Since the original QST article can be downloaded from this site in .pdf format, I will not attempt to cover the circuit theory or the test and alignment procedure in this write-up. 

Please download this file and print it off. Jim has made an excellent job of describing his circuit theory, schematic, construction details, alignment, and the summary is full of useful links relative to both DOS and Windows software.
Hey! as Jim said "Now you have no excuse for not trying Amtor, Fax, Hellscheiber, MT63, Pactor, Psk31, Rtty, SSTV, et al." For more information you can e-mail Jim at: n9art@arrl.net.

I have operated with most of the modules listed above and have ended up with the Isolated Circuit and both the Opto Isolated versions for RTS and DTR control. That configuration works great in this shack.
After my initial hook-up, and all ground loops removed, I still had problems with RF getting into the computer. I found that winding the cable to the computer speaker system through a Ferrite Core about 4 turns, removed this problem.
However, other Hams were not that lucky. I remember two other cases I was helping with where a Ferrite Core was needed in the Sound Card LINE IN lead and the other was wound in the Keyboard cable before a cure was effected. This process seems hit-and-miss at best so the best approach appears to be one of trial and error.
One very last word but not by any means the least--- IMD!  It is essential that your signal is clean on the air otherwise you will probably be splattering all over the band. On all the software available you will see a waterfall indicator which shows all the PSK traces available to you to work, however yours is NOT one of them. So how can you see what your signal looks like so you can take corrective action if needed? Well the other station will help you adjust your station until you have a fb trace or would you believe, there are indeed devices available that will allow you to see your own trace. Check out PSK Meter by KF6VSG or IMD Meter by KK7UQ.
Got a soundcard interfacing question? Take a look at this Forum: http://forums.ham-radio.ch/forumdisplay.php?f=30
To help me collect the different Radio hook-ups please send me this Form with your Radio's hookup information for publication on this page. Any comments or help would be really appreciated.
I
hope this page grows with the your help and that it is found useful when interfacing you system,
 73 de Ernie (WM2U)