[RTTY] Question

[Kok Chen]

On Jun 9, 2013, at 12:10 PM, Russ Guidry SR wrote:

> Had same problem, MMTTY lost it FSK config.

Dick's uses the SignaLink, and PKT mode on his FT-950, and thus AFSK.  

Dick: 

If the PTT light on the SignaLink USB is coming on when you transmit, then the SignalLink is getting the proper (at least some :-) audio signal, and the problem is not between the computer and the SignaLink.  

If the PTT light on the SignaLink does *not* come on and yet you are keying the rig when transmitting, the rig is being keyed by some other PTT signal -- you need to check your software to make sure it configured properly and you are not using FSK or something like that.

If the PTT light does comes on, you can confine your debugging to the SignaLink and FT-950.  The software is not likely to be the problem (except for tone pair selection -- read on).

The first thing you can check is to open up the SignaLink enclosure to make sure that silly DIP header that they use as a crossbar still has all the wires in place.  Check especially for the wire that connects the output audio from one of the transformers to the RJ-45 connector.    If the signals on the RJ-45 scopes out OK, the SignaLink is working fine, and you can move on to the FT-950.

First, check signals at the PACKET DIN connector at the rear of the FT-950. Make sure transmit audio is reaching the DATA OUT pin of that connector.  If not, the DATA OUT connection may be broken.  Happens often when there is no strain relief when you built that cable.  Make sure the DIN connector seats all the way into the rig :-).

Now, this next thing might sound stupid and counter-intuitive: but also check the MIC GAIN on the FT-950.  

If it is like the FT-1000MP's MIC GAIN control, the AFSK input through the DATA IN connector is controlled by the MIC GAIN knob.  If you turn the MIC GAIN of an FT-1000MP fully counterclockwise, you get no modulation from an AFSK signal.  (Some of the engineers that design amateur rigs aren't the brightest bulbs.)

If The MIC GAIN is at least more clockwise than the 12 o'clock position, and you can see a transmitted AFSK signal on the PACKET DIN connector, AND you are selecting PKT mode, check the Menu in the FT-950 to make sure you are using the same tone pair that your software is using.

If the FT-950 is like the FT-1000MP, there will be no 2215/2295 tone pair.  Instead, select the equivalent 200 Hz-shift Packet tone pair of 2110/2310, assuming that your software is set to transmit with a 2125/2295 tone pair (confirm that while you are at it).

The rule of thumb is that unless your ears really, really demand that you to use low tone pairs, pick the highest tone pair (usually 2125/2295 or 2110/2310) that is available in the rig, and switch the software correspondingly to use the same tone pair.  This will allow the transmit crystal filter to give you more protection from AFSK harmonics in case you unintentionally overdrive the AFSK signal.  

73
Chen, W7AY