Manual for DTR-MS Solid State Recorder


1. Introduction

1.1 Information about meteorscatter

2 General description ofthe DTR-MS

3 Installing the DTR-MS

4 Specifications of push-button keys

5. Description of functions

6 Appendix

7 Specifications

1. - Introduction

Congratulations and thank you for purchasing the digital tape recorder for Meteor Scatter (DTR-MS). We are confident that you will find this recorder to be very helpful for the successful execution of High Speed CW Meteor Scatter contacts. We believe to have covered in this instuction manual most questions about the use and applications of this recorder. In case however, that there are any questions left on details, please feel free to contact us and we will try to answer you and expend this manual. All suggestions will be very much appreciated.

1.1.- Information about meteorscatter

It may be very well possible that in reading this manual more questions arise. Quite often however, these questions are not so much related to the use of this recording device but to Meteor Scatter Operation in particular. Indeed, it could be about the physics of meteor scatter or how to operate using your radio and this form of propagation. It is not the purpose of this manual to cover or explain these important issues. In such cases, we like to suggest to the reader that he or she gets in contact with an active and experienced meteor scatter operator in order to discuss those questions and gain from the experience. If you have trouble finding such a person we will be glad to help in finding calls of stations, active on HSMS. Of course, we are also able to provide you with the desired information. Please, feel free to ask! Send us a letter, give us a phone call or write some lines via packet radio or e-mail to:

VHF-DX-Group DL-West,
c/o DL 8 EBW,
G. Juenkersfeld,
D-42327 Wuppertal,
eMail : DL8EBW

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2. - General description of the DTR-MS

The DTR-MS is a portable digital instrument enabling you to record audio signals for a maximum period of about 155 seconds ( this at a sampling rate of approx. 6,6 KHz ).
The DTR-MS has the ability to monitor already recorded data while still recording or data from a finished recording.
In both cases you are able to read the morse coded signals at nominal or at reduced speed with a normal or mixed modulation mode using the CPU. The mixer mode can be advantageous if you have to listen to a signal at reduced code speed and subsequently, the pitch frequency had gotten too low to hear.
Because of its small size and its sensitivity, the DTR-MS presents an efficient alternative to tape- or cassette recorders for the amateur who is interested in Meteor Scatter. These properties are particulary valued on field days, portable operations such as in from a car and expeditions where reducing weight and space counts.
The complete electronics package of the DTR-MS is mounted in a handy box of anodized aluminium.
To operate the recorder, it is only necessary to be familiar with 7 different function keys, located on top of the box. All data from the CPU is displayed on the big 7-segment LCD Display.
The required external voltage is between 10 and 15 V DC, so you might use the car-battery or an adapter such as used in the video-apparatus. After switching on the DTR-MS, the only connections you have to make are the AF-in and AF-out to the receiver audio connectors and then, you can step on the gas - -


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3. - Installing the DTR-MS

3.1. - Hints for the electrical installation

As is standard in a high-frequency environment, please keep the connections to and from the DTR-MS as short as possible. Avoid high voltage cables and strong magnetic fields in the vicinity as it could effect the performance of the DTR-MS in a negative sense. Make sure that the power supply connections and the audio lines make good contact and are properly shielded and grounded. Always check for the right polarity of the power supply to avoid problems!

3.2. - Diagram on the necessary connections

The DTR-MS has only 3 plug-ins, 2 audio signals and power. Please connect the lines as shown in the diagram below. Increase the AF-signal from your receiver into the AF-In Jack to the point at which the AF output level will not increase any longer. This is the optimum signal level for the AGC (automatic gain-control)!
DTR-Versions delivered after Feb. 15. 1995 will have a small LED at the edge of the display. ( see fig.2 ) This LED is "Dark" if the AF-lnput level is correct.(*) The optimum frequency for the audio signal from the receiver lies between 800 Hz and 1200 Hz, due to the recorder input filter characteristics.

(*) Former versions can be modified Connection diagram: (fig.1)

3.3. - Power supply

The DTR-MS works with an internal voltage regulator circuit. Therefore it is possible to use a voltage supply between 10 to 15 Volt DC. The maximum current needed amounts to about 350 Ma, so that you are able to use a simple AC/DC adapter which is used for video or phono applications. An internal diode protects the DTR-MS against errors in voltage polarisation.
Turn the Power Supply off before pulling or plugging in the DC connector to the DTR-MS!

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3.4. - Operating the DTR-MS

The DTR-MS is constructed as a recorder for portable use, but it can also be used in the shack at home of course. It can be operated within a wide range of temperatures and environmental conditions. Please use a solid support for your DTR-MS without strong vibrations, swingings or other harmfull factors to electronic equipment.

4.- Specifications of push-button keys

5. - Description of functions

The solid state digital recorder DTR-MS is a system for recording and replaying audio signals for a period up to 2.5 Minutes. For efficient and proper operation of the recorder, it is a must to be be familiar with all functions and function keys.

5.1. - The Recording the Audio Frequency signals

If you want to put the DTR-MS into the recording mode, and start to save data, you have to push the buttons <REC> and <MARK> simultaneously! The double function for these keys (the only one, at this time) is necessary to avoid unintentional recording over old records. When you push <REC> and <MARK> together, the display will show an undefined value when the audio input is connected - this is not a error condition! When the audio input is not connected the display will show a number aroud 128. (Adjustment of AGC). After releasing the buttons the counter will go to 000 (0-150 or 0-989 depending on the standard settings)
The red LED above the <REC> button indicates that you are recording. During recording, you can monitor the slightly filtered input signal at the AF output jack.

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5.2. - How to mark a burst

While receiving in meteor scatter mode, it is very important to know at what time in your record, the burst did occur so that you can quickly locate the desired information transmitted by your partner. Thus, you like to set a marker ( information counter ) right there, when you hear the desired signal. The DTR-MS provides this feature.
When you used your old tape recorder, you always had to watch your tape counter and write down the count where the burst occured. With the DTR-MS you only have to push an infomark (short <MARK>) and the CPU sets a special digital sign in front (!) of the burst-record. This will only happen when you immediately push the <MARK> button when you hear the signal during the burst. The CPU will take your reaction time into account and the setting mark will be a few milliseconds earlier in the recording. An identifying number for this marking ( for example -05 ) is shown on the display for about 1 second. The time, when the burst occured, is clearly defined with this number and can be found back later without any difficulty!
We recommended to train a bit on how to set these setting markers. After some skeds, you will have no problems with meteor burst marking.

5.3. - Playback

The playback-function can be done simultaneously during recording (at that time the signal is available on the recorder audio output jack or on the tranceiver speaker) or after the 155 sec. of recording have ended.( end of recording time ). The audio output for your headphone is adjustable by the only extern potentiometer at the side of the DTR-MS.

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5.3.1. - Simultaneous playback during recording

If you push the button <PLAY> while recording, you will get the signals from the start of the recording directly to the output! (counter starts at 000). The green LED above the Button <PLAY> indicates then, that you are in the playback mode. The red LED above the buttom <REC> indicates that you are also recording simultaneously in the background. If you detect a meteor burst during this playback, you can still with the <MARK> button set the markers. In this case you have to monitor a second speaker or watch the S-meter on your receiver for bursts. Remember, your are listening to an earlier part of the recording while recording in real time and at the detection of burst, put a marker in the real time recording.

5.3.2. - Replay after full recording time

When the full recording-time of 155 seconds is over, the counter will stop at the scaled value (989 or 155) and the red LED above the <REC.> button will be extinguished. Now the complete data set of 155 seconds recording is stored in the RAM and will remain so as long as you do not re-start the record mode by pushing simultaneously the <REC.> and <MARK> button or you shut down the DTR-MS. If you want to listen to all the information from the start of your record, you can push the <Play&gy; button. The green LED (above <PLAY>) indicates then that you are in the playback mode. The display shows the present position of your recording. The buttons < << > and < >> > enables you to move quickly through your recording from one position to another.

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5.3.3. - Playback using info marks

As shovn in chapter 5.2, the DTR-MS has the provision to store setting marks (up to 30!) ahead of the recorded information. So, when you mark a burst in that way, it is easy to find that sector back from the recorded data. In thar case, you are NOT to go into the playback mode (<PLAY> button). You must remain in the recording mode <REC.> or go to the stand by-mode ( end of recording-time or 155 sec.). At first, you have to push the buttons < << > or < >> > and the display will indicate your setting mark number (e.g. -05). Then, you go to the playback mode by pushing the <PLAY> button;. If you had set the marker at the correct time, you will hear, after a few milliseconds, the information come out of the noise. If not, use the < << > buttons and search over the last seconds of your record... perhaps your reaction had been a little bit slow when the burst occurred (in long MS-nights this can happen, hi). Perform this search only in the playback mode, because otherwise, if you return to the stand-by mode, you will only scroll between the marker numbers. By-the-way a start mark (I--) and an end mark (--1) are always present.

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5.3.4. - Playback at different speed

For efficient meteor scatter operations it is necessaly to use higher cw speeds than normally used. At present time the standard is 1000 Ipm, but this may change to higher speeds with the help of the DTR. The advantages of using higher code speeds, especially with short reflections, is shown in fig.3
Based upon the "paris" system you can see the amount of information in relationship to burst duration, calculated for various transmission code speeds rates. It is up to you to select by what factor you want to reduce the speed when you play back the transmission. You can choice to reduce the speed in steps from 1/2 to l/50 times the original speed (e.g.: 2000 lpm / 16 = 125 lpm or 25 wpm).(*) It does really not matter in which mode the DTR-MS is operating, you can always change the speed at which you are playing back with the button <SPEED>.
Push that button and the speed will go down by one division factor step. Every time you push the button <Speed>, the speed is shown for 1 sec. on the 7-segment display. If you hold the button longer than 300 ms., the speed will step down continuously ("scrolling" The last selected speed will persist until you disconnect the power or you change the factor manually.

(*) 1/22, 1/50 for DTR-Versions delivered after Feb. 15. 1995

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5.3.5. - Playback with modulation

If you reduce the speed of an audio signal during playback, you will find the pitch reduced in the same ratio. You are reach quite quickly the low end of the audible frequency spectrum (approximately 300 Hz). When using a tape recorder, this problem is normally solved by the use of an up converter. This circuit mixes the reduced frequency audio-signal with a sidetone. This however will create a mixing-loss of about 3-6 db! With the DTR-MS however, you get digital circuitry that calculates the optimum mixing when you reduce the play back speed. Therefore you will not hear any mixer-loss! with the button The mixing-factor for the desired tone can be selected by you With the <MOD.> button you can select the right mixing-factor for the desired tone. By pushing the <PLAY> button you place the DTR-MS is in the playback mode. You can now change the output pitch by pushing the <MOD.> button.
The factors for the mixing will be:

    PL.0 = no mixing.
    PL I = input tone x 2,
    PL 2 = speed correlated output tone
    PL 3 = input tone x 8.

The factors will not always be exact due to the calculations of the CPU for an optimum result. It depends heavily on how far you reduced the speed!. If you hold the button longer than 300 mS. the "PL factor" will step down continuously ( "scrolling" ).The mixer-factor <MOD.> will remain constant as long as you do not turn off the power or change the factor manually.
A simple example: We like to decode a CW MS high speed signal with a tone-frequency (pitch) of 1.2 KHz and and a code speed of 1000 lpm. If you feel comfortable copying code at 20 wpm, the speed should be reduced by a factor of approx. 12x and an output pitch should be generated for good audible copy, lets assume 750 Hz.

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          Speed                                               Frequency

         1000 lpm / 12       [ speed reduction 12x ]         1200 Hz / 12

          83 lpm             [    translates in    ]           100 Hz 

The speed of 83 lpm ( approx. 17 wpm ) is to copy comfortablely but a pitch of 100 Hz in the modulation "PL0" will be hardly audible in this situation. The best will be to select the faktor g ("PL3"). This will provide a pitch of 800 Hz as AF output!

          83 lpm                                             100 Hz x 8

          17 wpm                  at                         800 Hz

5.3.6 . - First results with the DTR-MS

The idea of designing and building the DTR-MS was born during the 120 hour long BCC-MS contest in 1993. A group of operators with DL8EBW & DF7KF worked only with one audio tape-recorder, used a lot of audio cassettes and was suffering from a headache.
Again, the expedition to Portugal of DF7KF in the year 1994 showed the same problems with the audio tapes during in the pile-ups and the recording of signals.

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6. - Appendix


6.2.3. - Configuration of the standard sample rate:

At the time of delivery the sample rate of 6,6 KHz is used.

S6 Off- S7 Off = approx. 6,6 KHz (Normal mode)

S6 On - S7 Off = approx. 10 KHz

S6 Off - S7 On = approx. 8 KHz

S6 On - S7 On = approx. 4 KHz

The intermal filter is specified for the Normal mode (6.6KHz!)

6.2.4. - Scaling of the counter:

S8 Off = counting in seconds

S8 On = counting 000-989 (989 full)

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7. - Specifications

                                Technical details:

   * Sampling rate:                            Approx.  6,6 KHz 
   * RAM:                                      1 MB
   * Max. Recording-time:                      Approx.  155 seconds
   * Max. Number od Setting-marks:             30
   * Speed Reduction:                          Variable down to 50x
   * Modulation:                               Signal mixing (up-converter),
                                               in 4 steps:
                                                -  No mix,
                                                -  Input qrg x2,
                                                -  Speed correlated output tone,
                                                -  x8
                                               Exp: Input tone  =    1000 Hz
                                               Speed reduction 10x -> 100 Hz
                                               Modulation x 8   =  800 Hz out
   * Special feature:                          Record / play possible at the same time.
   * AF-input:                                 400 mVss to 6 Vss, Impedance 17KOhm
   * Input level:                              AGC, CPU processed
   * Input filter:                             500-1800 Hz
   * AF-output:                                Approx 500 mW/8 Ohm (headphones etc.)
   * Function keys:                            7 keys
   * Display:                                  3 LED - 7 segment-display
   * Display-info:                             Counter in seconds or 0-989 
                                               (used as standard factory
   * Power supply:                             External PS 10-15 Volt DC @ 350 mA.
   * Housing:                                  Aluminium case, IP20  
   * Dimensions:                               Approx 170 x 100 x 45 mm (like normal TNC2)
   * Weight:                                   Approx. 500 gr.
   * Temperature range:                        0 C to 60 C
   * Humidity:                                 5% to 95% (non-condensing)
   * AF Keying:                                500 and 2300Hz tone,
                                               driven by a PC or Keyer
                                               PTT during TX
                                               Start of the DTR-MS+ at end
                                               of transmit.
                                               In and out switchable
                                               to the headphone
   Infos and orders:

   ADE Vertriebs GmbH,  Gewerbepark 5, 52388 Nörvenich, Germany
   Phone : 2426 / 900001   fax : ++2426 / 900001
   eMail :
   Price:  DM 494,50  incl. tax and shipping (EU)


Comments: Rein, W6/PA0ZN

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