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DSC Controler               By: Brian Reinhold

Design: This controller is meant to run on any PC under Windows that has a soundcard. The hope is that it will be able to be used without any special hardware. The controller is designed to be attached to a computer controlled watch receiver and a computer controlled secondary transceiver. The watch receiver and secondary transceiver are controlled by sending codes over serial (or USB serial) ports. The codes allow the controller to set frequencies of reception, transmission, power levels, bandwidths, AGC, etc. The idea is that all intelligence sits on the PC and the radio performs only radio functions, thus even features like scanning is controlled by the PC. The PC soundcard is then used to generate the DSC signals that go to the audio input of the transmitter and the alarms which generally go to the PC speakers. It is also used to digitize the DSC signals from the audio output of both the watch and secondary receivers for the subsequent handling by the controller. A fully functioning system would then consist of a PC with a soundcard having stereo Line In and Stereo Line Out jacks and three serial ports connected to a watch receiver, a secondary transceiver, and a GPS unit.

Not finished: What is missing at this stage is the GPS handler (written but not implemented into the code yet) and the radio controller codes. The problem with the latter is that there is no standard set of control codes for steering radios, and one has to write a different set of codes for every manufacturer (kind of like the old days of programming video cards in DOS). In the absence of real radios, there is a frequency simulator that can be used between two computers both using this controller. The frequency simulator should ONLY be used between two computers using this controller.

What is also "missing" is that the controller is not finished. It is an experimental test program and under continuous development. As a test program it can do a lot more and shows a lot more than any operational controller probably would. At this time its primary purpose is to test a proposed means of automating the operational procedures of the standard. It is also being designed as a possible means of certifying the functionality of DSC equipment. Because it is in a state of flux (not even a "beta" release) one can guarantee that it will have bugs. So its use is entirely at one's own risk.

Here is a little guidance, but I hope that most of the controller functions can be run without any manual.

Installation: Copy the file XWINDSC.EXE to any directory and run the program. First time use will require entry of an MMSI otherwise you won't be able to do any DSC stuff.

Program creates a file called XWINDSC.SAV which saves all the setup options and color options.

EXIT: The only way to exit the program is to click the close "X" button in the upper right corner of the big yellow background window!!

Sound Card connections: The controller uses the PC soundcard to send and receive DSC audio signals. Since a DSC controller listens to two receivers, a watch receiver and a secondary general receiver, the left channel of the stereo Line In port of the soundcard handles the watch receiver and the right channel handles the secondary receiver.

The microphone input port could be used but since the microphone is mono, the input signal will be received on both channels. This option is usually the only option one has on a laptop.

In either case, the Soundcard mixer software will have to set the device used for recording (either Line In or Microphone) otherwise the Soundcard will ignore any incoming signals. If the soundcard did not provide a mixer, the Windows Volume control can be used to set the record option under the "options" and then "properties" menu item.

The right channel of the Line Out port is used for transmitted DSC signals, and the left channel is used for alarms.

Direct X: The program uses Direct X for real time control of the soundcard hardware (like the game programmers). It should not pose a problem on any relatively new systems.

Computer to Computer operation: To use two computers to simulate DSC calls between two stations you need to connect the DSC Line Out of computer A to the right and left channels of the Line In of computer B. You could use the microphone port instead but you will have to set the signal strength to very small values (under the Special DSC Calls menu item). Do the reverse for computer B. The right channel of the Line Out can be connected to a speaker to hear the alarms if your sound card can't do both at once (the Soundblaster Live can, most laptops can't).

Be sure to turn the frequency simulator on (under the setup menu) or nothing will make much sense (especially using MF/HF) and to provide a NULL modem serial connection.

Radio connections: Radio controls will not work since there is no standard set of control sequences that steer radios. Special sequences have to be programmed for every type of radio. This coding has not been done. When it is completed for a given manufacturer, two serial ports will send control signals to the watch receiver and the secondary transceiver to handle tuning and channel switching. On HF these signals are very important as they control scanning.

Since there is only one VHF DSC channel, this controller will be able to receive DSC calls from any VHF radio tuned to channel 70. Just be sure the audio out of the radio is fed into the left channel of the Line In port of the soundcard. Upon reception of the DSC the controller will display the information and start the procedure of handling the event, but it will not be able to control the radio to do proper tuning.

IF you use the controller to listen to a real radio or signals generated by another controller, TURN THE FREQUENCY SIMULATOR OFF!!

What you see: When the controller is first started it is in standby. There is a yellow background screen, a window with the MMSI, current position, time of the position, and current UTC time, and a window with seven buttons. They are:

1. F2: Distress Alert: This button is used to compose a distress alert. Since a PC has no dedicated distress button, a simulated button will appear in the composition menu. When ready to send the alert, the button has to be pressed and held for 3 seconds before the alert attempt begins.

2. F3: Call a station: This button is used to compose a call to an individual station. The individual call is separated from all other calls as it is anticipated that it will be frequently used as it is the call most mariners will want to make. So why make them hunt for it amongst a bunch of esoteric calls that are almost never used? Using this button, all the operator then needs to do is enter the MMSI number of the desired recipient and press the Send Call button.

3. F4: Special DSC Calls: This button is used to compose all the possible types of DSC calls that do not contain the distress information. The resulting composition dialog box is complicated! All components and possible components of the call are displayed, and one can change between different ITU standards (the new, version 11, the previous, version 10, and no standard). In the lower right corner one can also play around with test signals. One can change the amplitude of the generated signal, and one can mess with the frequencies of the DSC tones. Using the sound card setup one can also mess with the baud rates of the DSC signals. If none of this sounds familiar to you, leave it alone! If it does get changed by mistake, you can reset everything by going into the setup menu, switching the radio type (VHF to HF or vice versa) and then switching back.

4. F5: Distress for someone else: This button is for the infamous DROBOSE (Distress Relay On Behalf Of Someone Else). This option is selected when one sees a vessel in distress that cannot send its own distress and thus one sends a distress on its behalf. Technically, the call is a distress relay. Its just as if one received a distress alert and then relayed it, however, in this case the distress alert was not received by DSC means.

5. F6: Radio Telephone: This button is used to establish direct radio telephone contact with another radio; a feature that is very popular on VHF. What this button does is establish an automated procedure for the communication link. That allows the operator to handle these direct calls in parallel with any DSC calls and not lose either.

6. F7: Enter Position: Pretty clear. Allows manual entering of the position.

7. F8: System Options: Here is the setup menu. Lots of stuff in here from setting the radio type, the soundcard features (be careful!), customizing the alarms, the station MMSI, and a whole slew of options from auto acknowledgment control to call editing.

In addition to the main menu there are two scanner windows. They are minimized upon start up and usually appear on the startup bar at the bottom of the screen. One is the priority scanner and the other is the general scanner. Clicking on these buttons will bring up a window with an oscilloscope feature and a bunch of channel lights. On MF/HF, the scanner will be going in both windows, and one will see the channels being sequentially lit as they are being scanned. In the oscilloscope window the received signal will be displayed.

This is a test program: It does a lot of things a DSC controller is not supposed to do. It runs the new 493.11 standard, the previous standard, and a free-for all, no standard. It can also receive (snoop) and respond to DSC calls not meant for the station.

Automated Procedures: The single most important purpose of this controller is to demonstrate the proposed new DSC automation standard, or "automated procedures" which is currently going through ITU and IEC. DSC calls are not handled as isolated items but as events. When you send an individual call to some station the procedure remains waiting for the acknowledgement. When the correct acknowledgement comes, the procedure responds, alarms and tunes the radio accordingly. One can send several calls to different stations and all the procedures will wait in the background for their acknowledgement. When acknowledged, only one procedure can actively communicate since there is only one transmitter. The other procedures will be "on hold" analogous to the common telephone feature, and the operator can actively switch between the procedures as per phone.

The automated procedures are of the greatest benefit for distress events. In that case, the first DSC of a distress event sets off the newly required two-tone alarm which must be manually silenced. After that, all DSC calls concerning the same distress event are handled by the single procedure. Any subsequent tunings of the secondary receiver (important on HF) are done automatically. Repeat received DSCs sound a brief self-terminating alarm. The procedure will not sound a "manual terminate only" alarm until the event is acknowledged. The procedure can also be placed on hold like any other procedure and the operator can engage in other traffic, and nothing of the distress event will be missed. On VHF the communications automated procedure means that the operator can use the VHF comms as desired and any incoming DSC will not be missed and it will not disrupt the communications. The operator is able switch back and forth between the DSC and standard communication events and not lose either.

MF/HF and VHF: The radio can run either as a VHF or MF/HF controller. It was designed as an MF/HF controller and the VHF is simplification of that. The option is in the setup menu. Stop all procedures and call compositions before switching between radio types. I have not built in a guard against that switching (yet), and if you change radio types in the middle of some procedure I have no idea what will happen. But I bet it will not be pretty.

Potential Problems and Warnings: The biggest problem so far that I have encountered is cheap sound systems on laptops and crappy filtering of their power adapters. The noise level can be notoriously high, especially on the microphone input. It is made worse by the use of unshielded audio cables which pick up anything and everything. In fact, I have yet to encounter a laptop which has a decent sound system. When using two computers, this noise tends not to be a problem as all one has to do is crank up the signal strength on the host computer (be careful when feeding into a microphone). But when listening to weak signals, there will be a problem. The problem is compounded on VHF which goes at a much higher baud rate and therefore it is much harder to separate the signal from the noise (in real life VHF is a lot cleaner than HF so that is okay). Since the noise is mostly internal to the laptop, having a clean signal off the airwaves doesn't help much. In many cases I have found running on batteries greatly reduces the noise, but that does not always solve the problem. On the bright side, I have not had nearly as much of ap roblem on my desktop, but it has a Soundblaster Live card. If you are serious about use of PC controllers, get a sound card used by musicians. They are good. The HAMs are also big on sound card run radio operations, and they have provided simple circuit diagrams that help solve many of the ground loop problems that develop between radio-PC connections.

© Brian Reinhold (2005)

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