Page 09 – Commercial Interfaces

Commercial Sound Card Interfaces

If you choose not to build your own audio interface cables or FSK/PTT interfaces, you can buy a commercially built sound card interface.

There are several commercial sound card interfaces available.  All of them should work with MMTTY and nearly all of them come with cables to interface to your transceiver (you must specify which cable you need).  However, not all of them are capable of keying FSK.  If you are using AFSK, they all should work.  Some of the manufacturers and their products are included on this page.  For more specific information, refer to each manufacturer’s website.

microHAM or

microHAM offers a very wide variety of interfaces that run RTTY and work with MMTTY.  These are excellent high-end devices.  I currently own an original microHAM micro KEYER and still use it on my 2nd radio for RTTY contesting.  Even though it was a beta unit that was one of the very first built, it has NEVER failed me or even hiccupped – ever.  Because there are a lot of different units available and because microHAM is constantly updating its line, its best to browse their site for more detailed information on their products.  Their support and documentation are excellent.  I highly recommend microHAM products for RTTY.

The RIGblaster

The RIGblaster is a very popular brand of sound card interface.  There are several models to choose from.  All work with MMTTY.

The most basic unit is the Nomic.  The next model in line is the Plug & Play.  Both the Nomic and Plug & Play (plus the discontinued M8 model) do not support FSK keying directly (except the Plug & Play – see next paragraph).  The Nomic is for AFSK operation only by offering an audio interface between the sound card and transceiver for both transmit and receive.  PTT is connected to the radio’s mic input.  Gert, K5WW, did build an FSK keying circuit inside his Nomic.  For details on adding FSK to a RigBlaster Nomic click here.

The Plug & Play model also does not support FSK directly, but it’s not impossible.  The Plug & Play has a built-in USB-to-serial adapter.  The unit supports PTT and CW outputs.  The CW output is keyed using the DTR line of the USB-to-serial adapter.  By using MMTTY’s EXTFSK feature, the CW line of the Plug & Play model can be used to key FSK by configuring EXTFSK to key DTR to FSK for the COM port assigned to the Plug & Play unit.

The Plus and Pro models fully support FSK (and CW) operation and have a separate output for PTT in addition to PTT on the MIC connection.  The Plus model outputs CW and FSK on the same jack though.  In order to change from CW to FSK, jumpers are changed inside in the unit or FSK can be set to key the DTR line by using MMTTY’s EXTFSK feature.  The Pro model has separate FSK and CW outputs.

The Pro model offers a variety of options for configuring radio control, PTT, CW and FSK when using both included serial ports.  Be aware that if you intend to use hardware PTT (a physical PTT connection between the Rigblaster Pro and your radio), then both PTT and FSK must come from the same COM port.  This means that P16 jumpers inside the Pro model must be configured so PTT and FSK are on the same port and the second port is used for radio control only for use with MMTTY.  However, if you want to use P16 jumper configurations that have PTT and FSK on separate COM ports, then you must key PTT via radio control.  Hardware PTT will not be employed.

The Navigator by US Interface

From reports received, the Navigator appears to be another excellent interface for RTTY (and other modes).  It offers direct FSK keying and a host of other features.

MFJ Sound Card Interfaces

MFJ offers two interfaces – the MFJ-1275 and MFJ-1279.  Both work with MMTTY.  The MFJ-1275 does not support FSK, but the MFJ-1279 does.  However, like the RIGblaster Plus, FSK and CW share the same output on the MFJ-1279.

RASCAL GLX by Bux Comm

Bux Comm offers one basic unit.  It comes in three flavors – Black, Beige and kit form.  All three are the same interface and will work with MMTTY.  The GLX supports FSK keying.  Bux Comm offers a very large assortment of cables to interface to just about any transceiver made.

SignaLink USB+ by Tigertronics

The SignaLink USB offers a unique circuit that senses audio from the sound card to activate PTT.  Therefore no connection to a serial port is required.  This is great for use with newer laptop computers that do not have serial ports.  However, it does not run FSK and must be used for AFSK operation only.

Final Comments on Commercial Interfaces

When shopping for a commercial interface for RTTY, it’s a good idea to get one that is capable of direct FSK keying.  Even if you don’t use FSK now for RTTY, eventually you should because it allows you to use narrow IF receive filters if your radio has a RTTY or FSK mode.  Also, when using FSK transmission, you don’t have worry about transmitting a distorted signal by over driving the audio or by hum on the transmit audio line.  Another problem with AFSK is that any sounds produced by the computer could accidentally be transmitted over the air and this is not good.

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