ICOM 718 RTTY Mode

[KB3MDT]

Hi,
    I've been successfully doing PSK, RTTY and a few other modes with my ICOM 718 and a Signalink USB interface.  Normally I set the ICOM's mode to USB or LSB.   I'm using FLDIGI for software.

    My rig also supports an RTTY mode.   I played with it a little and it doesn't seem to do anything differently for RTTY versus when I when I'm using the Signalink and USB.    Question - Thus, what does the RTTY Mode on the ICOM actually do?

73
KB3MDT
Ken

[VA7CPC]

you should check the manual, but usually:

. . . "RTTY mode" is used when you have an interface that does "true RTTY" or "mark/space keying".

For such an interface, the MARK signal is at one (DC) voltage, and the SPACE signal is at a different (DC) voltage.

The rig has circuitry that uses those voltages to shift the frequency of its carrier.  The MARK/SPACE signal is applied to dedicated RTTY pins on the 13-pin "ACC" connector on the IC-718.

The signal transmitted is the same as the signal using AFSK, where the audio MARK and SPACE frequencies are used as SSB modulating signals.  However, there are some technical reasons why "true RTTY" is preferred by some hams.

If you want to pursue this, there's an interface by W3YY:

http://www.eham.net/reviews/detail/8519

And there's probably more information at:

rttycontesting.com

.              Charles

[KO3D]

It's for true Frequency Shift Keying RTTY using a TNC rather than the sound card AFSK RTTY most of us now use on USB. As long as you are using a sound card for your RTTY, you don't need the 718's RTTY mode.

[AA4PB]

Probably the primary advantage of RTTY mode is that you can select the optional 500Hz CW filter for the receiver. In USB or LSB you have to use the wide SSB filter.

[VA7CPC]

On an IC-706:

. . . you can "lie" to the IC-706, and tell it that you've installed a "narrow SSB" filter, instead of
. . . telling the "truth" about the 500 Hz CW filter.

That lets you use the narrow filter for CW _and_ USB/LSB digital modes.

The sideband center-frequencies are not where they should be (for USB/LSB voice), but you can fix that with the IF SHIFT control.

If the Ic-718 has an "IF Shift" control, the same trick should work.

.            Charles