Here's a Collins Radio "MDM2001 HF MODEM", operational & in near new condition. No bends & no major scrapes & no dents - there are minor paint chips on the front panel edges and the unit has been installed in a rack. It is the standard 19" width, 1 3/4" in height, and 19 1/2" in overall depth.
On the front panel, the group of four green LEDs indicate that both CH1 & CH2 are both transmitting & receiving data. The +5V lamp is lit, as is the neon POWER indicator. The red FAULT lamp is off. There is a SELFTEST pushbutton switch on the front panel, as well as a small cover over two dipswitches (these dipswitches are used to set up parameters for the modem's serial control port as well as set up the MDM2001 addressing - up to 16 MDM2001s can be controlled by the software that comes along with it).
The rear panel has three connectors on it. A standard DB-25 female connector connects to a PC for MDM2001 control & status. A standard DB-25 male connector carries both transmit & receive audio for both MDM2001 channels. A female DB-50 connector carries all digital data to & from both MDM2001 channels. Levels are all RS-232.
The screenshots below are from a WIN95 machine and the MDM2001 software is running on it in an MSDOS window. The MDM2001 software also runs fine under even more primitive conditions - AOK on a 16 MHz 80386 running MSDOS 4.0...
This unit was manufactured in the early 1990s and uses Digital Signal Processing on both the transmit & receive side. There are two separate channels in the MDM2001 and they can operate independently & simultaneously. Either channel can be configured to operate in one of ten different modes - this from the manual:
1. - Basic 16 Tone Mode, compatible with Rockwell's TE-233A, TE-233B, TE-233C (MIL-STD-188-C PARA 7.2.1 & 7.3.5, MIL-STD-188-110 APPENDIX A)
2. - 16 Tone Enhanced Mode, compatible with Rockwell's TE-233P-6, TE-233P-7 (MD-1239), & TE-233P-8 (MD-1268)
3. - 16 Tone MD-1061, compatible with Magnavox's MX-513B (MD-1061)
4. - Single Tone, compatible with Harris RF-5254B (MIL-STD-188-110, PARA 5.3)
5. - 39 Tone Enhanced, compatible with Harris RF-3466A (MIL-STD-188-110, APPENDIX B)
6. - FSK Wireline Modes, compatible with TH-22 (MIL-T-55255A) & Stelma's MD-674 (MIL-STD-188-110, PARA 5.2) plus many other military wireline items
7. - TE-204 FSK, compatible with Rockwell's TE-204 (AN/USC-11)
8. - CV-786 Wideband FSK, compatible with Rockwell's 700B series and of course the venerable but still as popular as ever CV-786/TRC-75...
9. - MD-522 RTTY FSK, compatible with the MD-522 (MIL-M-55529A), in 850 shift & 85 shift & 85 shift diversity modes (850 shift in this mode is the one to use with military standard 850 shift RTTY, as used on clatternet Saturday mornings on 10137 USB at 0930 Pacific prevailing time...)
10. - 8-Channel VFCT FSK, (MIL-STD-188-342) "Voice Frequency Channelized Telegraphy" FSK mode is compatible with the Frederick 1290 and many other 8 channel multiplex systems
Of the above modes, most all can be run simultaneously on both channels of the MDM2001. There are two exceptions:
"Single Tone" (mode 4) cannot run on both channels due to processor realtime limitations.
8-Channel VFCT (mode 10) can run only on one channel due to I/O line limitations.
Below are a number of screenshots taken of this modem operating. For these pix, I have set the screen up to use the small 8X12 font to make for faster downloads, but while running the MDM2001 software under Windows you can set up the MSDOS window to use any font available to you, as large as you like - the window will size itself accordingly...
The left side shows the Invocation screen - it's what you get when you start the program.
The right side shows the System Configuration Editor - here you must configure the PC's serial port to match the dipswitch settings under the small cover on the MDM2001 front panel.
The left side shows the Modem Configuration Editor. This software can control up to sixteen MDM2001 units, but only one is connected here. The screen shows that both channels are set up to run Preset #12 (here, Preset #12 is set to "39 TONE").
The right side shows all sixteen possible preset configurations for this particular MDM2001. Each preset can be selected from the eleven possible MDM2001 modes, and then can be customized as desired. (If you so desired, you could set up all sixteen presets to be WIRELINE mode, but with different MARK & SPACE frequencies, different baud rates, etc., etc.) The text in the column under "PRESET DESCRIPTION" can be changed to describe each one of the sixteen MDM2001 modes.
The left side shows the selftest screen. Here, both Channel 1 & Channel 2 have passed selftest #2.
The right side shows a status display of all modems connected to the PC. Here is a single modem named MDM01, and both it's Channels are running in 39 Tone mode and both are KEYed.
The left side gives us a more detailed status report for one particular MDM2001. Again, 39 Tone, KEYed, Transmitting Data, Receiving a Signal, Receiving Decoded Data, and with a receive signal frequency offset of 0 Hz. & good signal quality. Ditto for Channel 2 of this particular MDM2001.
If we select "1Modify" in this left side screen, we get a display like the one shown on the right above. Here, we can modify individual parameters used in one of the selected MDM2001's channels.
Using the left side screen, we can select which of the sixteen possible mode presets we will assign to a given Channel in the selected MDM2001.
The right side screen above is the parameter editor for VFCT mode. Voice Frequency Channelized Telegraphy mode has up to eight separate MARK & SPACE tone pairs in the MDM2001's audio passband, and you can go in and fiddle with most anything you see on this screen. You can map different tone pairs to different I/O pins, you can disable any number of the eight tone pairs, you can change tone pair center frequencies & shifts & baud rates, you name it.
The manual has this to say about VFCT mode:
"Endless combinations of modes may be arranged by the user, using less channels and using higher shift frequencies that support higher maximum data rates on each channel. Have at it."
"Using this multi-channel capability, baud rates may be mixed from channel to channel with no exceptions."
The left side shows MDM2001 Channel 1 set up for WIRELINE use and with it's parameters selected to emulate Amateur Radio's 170 Hz. shift 45 baud RTTY tone frequencies.
The right side shows MDM2001 Channel 1 set up in one of the more exotic modes, running 2400 bits/second in a diversity mode with doppler tracking. Pretty amazing - 2400 bits/second over an HF radio link...
All this blather makes using the MDM2001 look real complicated. It is not. The user interface is very intuitive and easy to get used to - it is much easier to use than it is to explain.
download manual.pdf (over 20 megabytes)