Post by va3css on Mar 4, 2005 21:52:38 GMT -5
SSTV - or Slow Scan TV, is a method of sending still pictures from your computer to another Ham operator via the radio.
During a time when I was "in between addresses," I had made a custom interface between my laptop and my mobile rig in the car. Those two, plus a digital camera was all I needed to be SSTV on the go.
My mobile rig at the time was a Yaesu FT-7100M. It had a TNC port at the back of the rig which was exactly the same as a PS/2 port on a computer (used nowadays for most keyboards and mice). That made finding my own connector for it easy and cheap.
I went out and purchased a 6ft. PS/2 extension cable at a local computer shop, (the shortest they have). I promptly cut off the female end of the cord and bared the wires. Being in the computer world already, I knew the pinouts of a generic PS/2 extension cable. For those who don't know, (or care) a simple continuity check on each pin would tell you.
Then, using the rig's own manual, I matched the pinouts of the socket to my purposes.
To interconnect your PC to a rig for SSTV, you only need these basic things:
There may be some other possible connections to your TNC port, but these are the only ones you need for SSTV use.
Keep in mind that computers have STEREO sound, but Amateur Radio is still monoral. You can either connect only one of the two stereo channels to the rig, or just twin the two channels together, forcing mono. I usually do the latter, to prevent the possibility of having your Balance control on the computer over to one side, muting the output.
For the computer end of the interface, I purchased a simple male to male 1/8" stereo plug cable, which you can find almost anywhere. They're used most often to connect a set of speakers to your computer; or between a portable stereo and another; etc. It's a very common cable that even a dollar store would carry. The shortest one available is all you need, as you need to cut it in half anyways. One will become the LINE OUT connector, (PC to Rig) and the other for LINE IN (Rig to PC).
The other connector I needed was a female DB9 connector for my serial port on the computer for automatic key / unkey. If you choose to use a footswitch, then skip this one. You can get one from your local PC dealer, either separately, or from any serial cable of any kind (null modem; extension cable, whatever). Simply cut off the DB9 end with about a foot or so of wire, whatever you need. You might need to do a continuity test to locate the wires. You'll need pins 5 and 7 from a DB9, which are SG and RTS respectively.
SG = Signal Ground
RTS = Request To Send
In my particular case, the pinouts of the 7100M are as follows:
Pin Function
1 Packet Data IN (10 Ohm impedance)
2 Singnal GND
3 PTT (short to GND for transmit)
4 9600baud RX data
5 1200baud RX data
6 SQL control (+5V to open, 0V to close)
I ignored pins 5 and 6. I had no need to control the squelch for SSTV, and the computer's sound input is analog. The "speed" of the sound in is irrellevant, but sending it faster probably makes more sense to the PC, so pin 5 is not needed.
One of the 1/8" stereo plugs wired between pins 2 and 4, and the other between pins 2 and 1. For both, the SHEILD of the 1/8" plug cable went to pin 2. The other two leads I attatched together, forcing mono sound out to and into the computer from this interface.
The Line IN connection on the computer was from the 9600baud RX pin 4. The Line OUT connection on the computer was from the Packet Data IN pin 1.
That takes care of sound into and out of the PC.
To automatically key the rig from the computer, I wired a relay in between the RTS and CTS leads from the computer, and pins 2 and 3 on the rig TNC end.
The RTS lead is a 12V DC lead. When the computer wants to SEND data, (key the rig) it will sent +12V to RTS. When the computer wants to STOP the flow of data, (unkey the rig) it will negate RTS, changing it to -12V.
Then of course, the leads of the relay only have to short pins 2 and 3 on the rig end to "key" and "unkey" the rig.
Voila! Some solder; cheap cables, stripped and re-wired; add some ferrite beads; a couple test transmissions with some locals to get the levels right, and I'm SSTV mobile!
During a time when I was "in between addresses," I had made a custom interface between my laptop and my mobile rig in the car. Those two, plus a digital camera was all I needed to be SSTV on the go.
My mobile rig at the time was a Yaesu FT-7100M. It had a TNC port at the back of the rig which was exactly the same as a PS/2 port on a computer (used nowadays for most keyboards and mice). That made finding my own connector for it easy and cheap.
I went out and purchased a 6ft. PS/2 extension cable at a local computer shop, (the shortest they have). I promptly cut off the female end of the cord and bared the wires. Being in the computer world already, I knew the pinouts of a generic PS/2 extension cable. For those who don't know, (or care) a simple continuity check on each pin would tell you.
Then, using the rig's own manual, I matched the pinouts of the socket to my purposes.
To interconnect your PC to a rig for SSTV, you only need these basic things:
- Sound from your rig able to go into your computer, preferably into Line in of your sound card (most likely a 1/8" stereo plug).
- Sound from your computer able to go into your rig, preferably from Line Out of your sound card (again, most likely a 1/8" stereo plug also) I recommend Line Out rather than the usual "speaker out" that most of us use for our speakers for two reasons: a) much less output voltage from the computer - spare your rig, please! b) you can keep your computer speakers as they are on the computer - you won't have to unplug them to connect your SSTV setup, then change back.
- A connection from a serial (or COM:) port on your computer to your rig, to control keying / unkeying the rig. If you prefer, you can use a footswitch instead.
There may be some other possible connections to your TNC port, but these are the only ones you need for SSTV use.
Keep in mind that computers have STEREO sound, but Amateur Radio is still monoral. You can either connect only one of the two stereo channels to the rig, or just twin the two channels together, forcing mono. I usually do the latter, to prevent the possibility of having your Balance control on the computer over to one side, muting the output.
For the computer end of the interface, I purchased a simple male to male 1/8" stereo plug cable, which you can find almost anywhere. They're used most often to connect a set of speakers to your computer; or between a portable stereo and another; etc. It's a very common cable that even a dollar store would carry. The shortest one available is all you need, as you need to cut it in half anyways. One will become the LINE OUT connector, (PC to Rig) and the other for LINE IN (Rig to PC).
The other connector I needed was a female DB9 connector for my serial port on the computer for automatic key / unkey. If you choose to use a footswitch, then skip this one. You can get one from your local PC dealer, either separately, or from any serial cable of any kind (null modem; extension cable, whatever). Simply cut off the DB9 end with about a foot or so of wire, whatever you need. You might need to do a continuity test to locate the wires. You'll need pins 5 and 7 from a DB9, which are SG and RTS respectively.
SG = Signal Ground
RTS = Request To Send
In my particular case, the pinouts of the 7100M are as follows:
Pin Function
1 Packet Data IN (10 Ohm impedance)
2 Singnal GND
3 PTT (short to GND for transmit)
4 9600baud RX data
5 1200baud RX data
6 SQL control (+5V to open, 0V to close)
I ignored pins 5 and 6. I had no need to control the squelch for SSTV, and the computer's sound input is analog. The "speed" of the sound in is irrellevant, but sending it faster probably makes more sense to the PC, so pin 5 is not needed.
One of the 1/8" stereo plugs wired between pins 2 and 4, and the other between pins 2 and 1. For both, the SHEILD of the 1/8" plug cable went to pin 2. The other two leads I attatched together, forcing mono sound out to and into the computer from this interface.
The Line IN connection on the computer was from the 9600baud RX pin 4. The Line OUT connection on the computer was from the Packet Data IN pin 1.
That takes care of sound into and out of the PC.
To automatically key the rig from the computer, I wired a relay in between the RTS and CTS leads from the computer, and pins 2 and 3 on the rig TNC end.
The RTS lead is a 12V DC lead. When the computer wants to SEND data, (key the rig) it will sent +12V to RTS. When the computer wants to STOP the flow of data, (unkey the rig) it will negate RTS, changing it to -12V.
Then of course, the leads of the relay only have to short pins 2 and 3 on the rig end to "key" and "unkey" the rig.
Voila! Some solder; cheap cables, stripped and re-wired; add some ferrite beads; a couple test transmissions with some locals to get the levels right, and I'm SSTV mobile!
