Configuring FT 991A for native FSK RTTY mode

[How to] Configuring your FT-991/A for Native (FSK) RTTY mode.

Introduction

This is a step by step setup guide to setup the native RTTY encode mode of the 991/A, using RTTY-LSB mode instead of the Data-LSB, which we commonly use in other modes.

Note: In RTTY mode, it is usual to have it done in LSB mode, irrespective of the band - as in FT8 the USB mode is chosen, irrespective of the band.

In this example we will be setting up the FT-991A in FSK mode, using the USB port and MMTTY as the RTTY software.

In FT-991/A, the RTTY-LSB mode provides a convenient way to encode RTTY - it outputs a constant carrier (like in CW) and have the carrier shifted to encode the RTTY in the presence of a serial port signal. We usually provide the radio the encoded/modulated/ready signal to be transmitted via the sound card - but this also requires proper audio level driving, ALC, distortion control and other hassles. In RTTY native mode, you don't have to worry about it - all you need is the serial port signal (or the SHIFT pin on the rear port) to 'tickle' the carrier - so the radio can actually 'modulate' the RTTY signal. For correctness, shift the signal; this is why it it is named FSK mode.

I choose to use the RTTY native (FSK) mode due mainly to not having to take care of the audio control/loudness feed to keep ALC in reins - this is all taken care by the radio itself.

AA5AU gives an great explanation describing AFSK and FSK advantages and pitfalls. An tl;dr by me describing AFSK and FSK is:

• AFSK - You feed the audio generated on the computer to your radio, modulated and ready to be transmitted (like done in FT8);
• FSK - You "tickle" the Shift/Serial pin and then the radio will modulate it.

FSK advantages, by AA5AU verbatim: I prefer FSK because it’s straight on/off keying into the FSK input of my radio. I don’t have to worry about the audio level or whether I forgot to turn the speech processor off. I can then use the FSK mode on my radio along with the narrow 250 and 500 hz filters. When I switch from SSB to RTTY, I only have to change the mode on my radio.

In the end, the resulting transmitted signal will be (almost) just the same. I went the FSK route to give some use to the Standard COM Port, leaving the Enhanced port free for other uses, use the native RTTY-LSB mode - and I do agree with AA5AU's opinions too.

So without further ado:

Configuration

1. First thing, identify what's your Standard COM port (not the Enhanced!!!!!). Open the Windows' Device Manager. In the below example, it is COM5. Write it down.

2. Download and install MMTTY (link)

3. After installing, open MMTTY. Go to menu Option, select Setup MMTTY

4. Go to the SoundCard tab. In Reception, choose the interface that contains USB Audio CODEC. No need to choose an Transmission audio card. Do not click OK yet.

5. Go to the TX tab. In the PTT & FSK Port clause, scroll all way down to the bottom and select EXTFSK64. Do not click OK yet.

6. Now, move to the Misc tab. In TX Port, select COM-TxD(FSK). Now, click OK.

7. Next step; configure the EXTFSK. Click the RTTY icon in the task bar, select the below EXTFSK program.

8. In Port, select the COM port that you found in Step #1. In FSK Output, select DTR. In PTT Output, select RTS. Click the trace next to the OK status to minimize.

9. Now, to the radio. Go to the Configuration Clause 060 - PC Keying - Choose RTS

10. Scroll down to the configuration 096 - RTTY SHIFT PORT - choose DTR

11. Hit the MODE button on the radio, select RTTY-LSB

12. You are all set!!

Tune to the proper RTTY frequency in the band, hit the MMTTY's CQ2 button and enjoy!

Hope that helps; 73 de PY2RAF.

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