drm receiver 9835-1

RF&COMMS

12 Elektor Electronics 3/2004

Build Your OwnDRM ReceiverA digital radio for 500 kHz to 22 MHz

Design by B. Kainka

One again Elektor Elec-tronics makes its com-petitors take a very dis-tant back seat by pub-lishing the world’s firsthomebuilt DRM receiverfor digital (MP4-quality)broadcasts in themedium and shortwavebands. The receiver is ofa surprisingly simpledesign and supplies a 12-kHz output signal foreasy connection to yourPC’s soundcard whichhandles the demodula-tion and MPEG decod-ing. The receiver is alsotuned by the PC via anRS232 link.

RF&COMMS

133/2004 Elektor Electronics

times — first, a variable oscillator frequencyis used to mix it down to a fixed intermediatefrequency (IF) if 455 kHz. This provides thestation tuning on the receiver. The secondheterodyning operation is against a fixed467 kHz signal in order to mix the 455-kHzsignal down to 12 kHz. Using receiver termi-nology, the DRM receiver is a ‘double-conver-sion’ or ‘super-heterodyne’ type. The firstinjection signal is obtained from a synthe-

On 15 December 2003, DRM (DigitalRadio Mondial) entered a new phaseon the shortwave and medium-wavebands. The encoding was changedto MP4 in order to improve the qual-ity of the received audio signals evenfurther. The unique receiverdescribed in this article was devel-oped for all readers interested in lis-tening to DRM broadcasts at a mod-est investment.

One of the targets set for thedesign was good receiver perfor-mance without any adjustmentpoints. No special inductors or tuningcapacitors are used in this project,just off-the-shelf fixed inductors. This,we hope, encourages those readerswith more experience in digital elec-tronics than RF design and construc-tion. There’s no adjustment to worryabout and no need for special testequipment. A very simple software-driven alignment is sufficient to illu-minate tolerances in the oscillator fre-quencies used in the circuit.

The basic operation of DRM and inparticular its signal encoding andtransmission method was describedin Elektor Electronics December 2002[1]. Exactly one year later, in theDecember 2003 issue [2] we ran anarticle describing how DRM signalscould be picked up and turned intoaudio using an experimental receiverbased on our DDS RF Signal Genera-tor and a PC or notebook. The pre-sent DRM receiver also contains aDDS (direct digital synthesis) chip.The two articles mentioned aboveprovide a good technical backgroundto the workings of DRM and werepublished at a time when none ofour competitors was able to come upwith technical specifications on DRMlet alone an experimental yet repro-ducible receiver. The publication ofthis article is sure to increase thedistance.

A DRM interfaceIt is perfectly possible to view thereceiver as a DRM interface for thePC. As illustrated in Figure 1a, theDRM receiver has two links to thePC. By way of an RS232 connection,it gets digital control information fortuning the DDS to the desired DRMbroadcast station.

As opposed to a normal radio or

general coverage receiver the DRMreceiver does not supply an audiosignal you can make audible usinganalogue means like headphones, aloudspeaker or an audio amplifier.Internally, the DRM receiver mixesthe signal received from the DRMstation down to an IF (intermediatefrequency) of 12 kHz. Its outputtherefore supplies a mix of modu-lated carriers that together conveythe audio signal in the form of a dig-ital datastream. This DRM spectrum,a mix of various frequencies coveringa bandwidth of 10 kHz, is connectedto the Line input of the PC sound-card. Alternatively the Microphoneinput may be used if the signal israther weak. The DRM signal is digi-tised by the soundcard, while a spe-cial DRM receiver program looksafter the demodulating of the DRMsignal as well as the decoding of theMP4 datastream. Again, all demod-ulation and decoding is done in soft-ware. The resulting hi-fi stereo audiosignal is then available at the outputof the soundcard for reproducing bya (PC) loudspeaker or headphones.

Double-conversionAs you can see from the block dia-gram (Figure 1b), the signal receivedfrom the DRM station is mixed two

PC

030365 - 1 - 12a

Soundinput

RS232

DRMreceiver

PC

030365 - 1 - 12b

455 kHz

455 kHz 455 kHz

15895 kHz

15440 kHz

antenna

467 kHz

12 kHz

Soundin

RS232

467 kHz

Synthesizer

12 kHz

COM1

COM2

Figure 1a. The DRM receiver has twoconnections to the PC: a serial link for thereceiver tuning and a connection feeding anMPEG datastream to the Line or Microphoneinput on the soundcard. All decoding anddemodulation is done in software.

Figure 1b. The block diagram of the DRM receiver reveals a double-conversion (‘super-heterodyne’) design with intermediate frequencies at 455 kHz and 12 kHz.

sised oscillator supplying an output fre-quency that’s programmable by means ofcontrol data generated on the PC and sent tothe receiver over the RS232 link. The secondinjection signal at 467 kHz originates from aceramic resonator.

Practical circuitThe block diagram is easily found back in the

circuit diagram shown in Figure 2.The DDS oscillator based around IC2supplies an output signal to the firstmixer (MIX1) via a buffer stage, T1.In case you’ve never seen such abeast, MIX1 is a wideband double-balanced diode ring mixer. The IFsignal at 455 kHz is taken through asteep ceramic filter (Fl1) with 12-kHzbandwidth. An IF amplifier stage

around T2 raises the level by about20 dB before the signal is applied tothe second mixer comprising (pas-sive) FET T4, a type BF245. The sec-ond injection oscillator is frequency-stabilised by a CSB470 ceramic res-onator (X1) whose nominal outputfrequency is pulled down by 3 kHz toarrive at 467 kHz. The 12-kHz IF sig-nal at the drain of T4 goes through a

RF&COMMS


TUF-1

MIX1

1 42

3

K2

ANT

T1

BF494

R5

36

Ω

R4

18

0Ω

R3

33

0Ω

R2

68

0Ω

R1

3k

9

C7

100n

C6

15p

C5

15p

C3

100nC8

100n

C9

1n8

C10

3n3

C11

100n

T2

BF494

R8

2k

2

R6

10

0k

R7

100Ω

L2

10µH

L1

3µH3

L3

100µH

T3

R10

2k

2

R11

22

0k

R12

1k

R13

10

0k

R16

56

0k

R15

56

0k

R17

27

k

R9

100Ω

R14

3k3

R18

220k

C15

470p

C16

470p

C20

4n7

C18

1n

C1

100n

C2

100n

C4

100n

C23

100n

C24

100n

C14

100n

T4

BF245C

C17

100n

C19

1n C22

470n

2

3

1IC3.A

6

5

7IC3.B

C13

4µ7

X1

CSB470

C21

4µ7

C12

4µ7

+5V

+5V

BC548C

7805

IC4D1

1N4001

K3+5V

IC3

8

4

+5V

4 61

IC1.B

1 31

IC1.A

10 81

IC1.C

K1

SUB D9

1

2

3

4

5

6

7

8

9

IC5

XTAL

5

8

4

+5V

FSELECT

AD9835

FS ADJ

REFOUT

SDATA

FSYNC

REFIN PSEL1

PSEL0

IC2

SCLK

COMP

DVDD AVDD

DGND AGND

IOUT

MCLK

16

15

13

14

10

11

12

7

4

5

8

9

1

2

3

6

IC1

14

7

13 111

IC1.D

12kHz

IC3 = LM358IC1 = MC14899V

50MHz

RTS

TXD

DTR

C25

100n

Fl11

2

5

3 4

CFW455F

030365 - 11

16V

16V

16V

K4

3V

0V4

5V

2V3

4V8

0V7

2V4 2V4

2V4

2V4

1V2DC

0V5AC

IF

Figure 2. The practical circuit of the DRM receiver is marked by PC-driven tuning of a DDS oscillator and two large-signal resistant mixers.

simple bandpass filter before it is bufferedand amplified for another 20 dB by twoopamps, IC3.A and IC3.B. The output of thesecond opamp supplies the MPEG datas-tream to the PC soundcard input via couplingcapacitor C22.

The nitty-gritty of DRM reception is notstability or even spectral purity butextremely low phase noise of the injectionoscillator. In this respect the DDS VFO getsfull marks because it fully meets this require-ment, hence our DIY DRM receiver is anexcellent performer. Another importantdesign consideration, large-signal response,is fully covered by the passive double-bal-anced mixer used. The results obtained fromour prototype were impressive, to say theleast: with a simple wire antenna connectedto the receiver input, the DRM softwareachieves 30 dB quieting, a value onlymatched by expensive receivers.

Because a couple of characteristics thatare crucial in the context of AM reception areless important with DRM, the circuit is ableto achieve such excellent results despite theheavily simplified and alignment-free realisa-tion.

The joint dynamic range of the DRM soft-ware and the PC soundcard is sufficient tocope with signal variations of up to 30 dB,which are not uncommon on SW and MW.This conveniently saves on an ALC (auto-matic loudness control) circuit. High receiversensitivity is not an issue for DRM. Very weakDRM signals (say, below 10 µV) do notimprove by increasing the receiver gainbecause the actual signal to noise ratio isinsufficient at a large bandwidth like 10 kHz.A number of practical tests proved that thereceiver can make do without a tuned front-end. For one, the image frequencies at a dis-tance of 910 kHz (2 x 455 kHz) will nearlyalways fall outside the neighbouring broad-cast bands. On the other hand, the DRM soft-ware is remarkably tolerant of interferencethrown at it.

Of course, the above considerations shouldnot keep you from using a preselector and amatching antenna if you have a fine combi-nation available. If not, rest assured that a 3-10 m long free-hanging wire is sufficient fordirect connection to the mixer RF input.

DetailsThe antenna input directly on the double-bal-anced TUF-1 mixer has an impedance of 50 Ω.The mixer does the frequency conversion to455 kHz at a low impedance. The TUF-1 isdesigned for a frequency range of 2-600 MHz.However, it may operate below 2 MHz withsome reduction in the input impedance and

RF&COMMS


C5

C6C7

C8C9

C10

C11C12

C13

C14

C15

C16

C17

C18

C19

C20

C21

C22

C23C24

C25

D1

FL1

H1H2

H3H4

IC1

IC3

IC4

IC5

K1

K2

K3

K4

L1

L2

L3

MIX1

R1

R2

R3

R4

R5

R6R7

R8

R9

R10

R11

R12

R13

R14 R15R16

R17R18

T1

T2

T3

T4X1

030365-1

T

T

1

C1

C2

C3

C4

IC2

COMPONENTS LIST

Resistors:R1 = 3kΩ9R2 = 680ΩR3 = 330ΩR4 = 180ΩR5 = 39ΩΩR6,R13 = 100kΩR7,R9 = 100ΩR8,R10 = 2kΩ2R11 = 220kΩR12 = 1kΩR14 = 3kΩ3R15,R16 = 560kΩR17 = 27kΩR18 = 220kΩ

Capacitors:C1-C4 = 100nF, SMD, case shape

1208C5,C6 = 15pFC7,C8,C11,C14,C17,C23,C24,C25 =

100nF, lead pitch 5mmC9 = 1nF8, lead pitch 5mmC10 = 3nF3, lead pitch 5mmC12,C13,C21 = 4µF7 16V radialC15,C16 = 470pFC18,C19 = 1nF, lead pitch 5mmC20 = 4nF7, lead pitch 5mmC22 = 470nF

InductorsL1 = 3µH3L2 = 10µHL3 = 100µH

Semiconductors:D1 = 1N4001T1,T2 = BF494T3 = BC548C, BC549C or BC550C

T4 = BF245CIC1 = MC1489NIC2 = AD9835 BRU (Analog Devices)IC3 = LM358NIC4 = 7805IC5 = 50MHz oscillator module in 8-

way or 14-way DIP case

Miscellaneous:K1 = 9-way sub-D socket (female),

angled pins, PCB mountK2 = 2 solder pinsK3 = mains adapter socketK4 = cable with 3.5-mm mono or

stereo jack plugMIX1 = TUF-1 (Mini Circuits)FL1 = CFW455F (455kHz ceramic

filter, bandwidth 12kHz) (Murata)X1 = CSB470 (470kHz ceramic

resonator) (Murata)RS232 cable with 1:1 pin connections,

plug and socket, no zero-modem orcrossed wire cable.

PCB, order code 030365-1*Disk, PC software DRM.exe, order

code 030365-11* or FreeDownload

* see Readers Services page or visitwww,elektor-electronics.co.uk

Suggested component / kit suppliers:- Geist Electronic

(www.geist-electronic.de)

- Segor electronics (www.segor.de).

- AK Modul Bus(www.ak-modul-bus.de)

Figure 3. The PCB is double-sided and through-plated. All parts in the RF sectionshave to be soldered with the shortest possible lead lengths.

the occurrence of a strong inductive compo-nent. In practice, however, the receiver wasfound to work satisfactorily even down to500 kHz in the MW range.

The output of the ring mixer is connected toa wideband matching network for 455 kHz.The impedance is stepped up using a reso-nant circuit with a 1:10 ratio capacitive tap.The result is an impedance of about 1 kΩ tosuit the CFW455F ceramic filter. High accu-racy is not an issue here because the actualantenna impedance will typically be higherthan 50 Ω. The resonant circuit employs afixed 100-µH inductor with a low Q factor(<10), ensuring a bandwidth greater thanabout 50 kHz yet avoiding component toler-ance issues. Consequently, no alignment isrequired on the inductor while the step-upmatching circuit still adds to the remote signalrejection of the IF filter.

The CWF455F has a bandwidth of 10 kHz,with 10 kHz being occupied by DRM and theremaining 2 kHz, well, harmless. Actually, alittle more bandwidth is important to have asit provides a way of compensating frequencydeviations of the second injection oscillator.For example, if the oscillator runs at 467.5 kHzinstead of 467.0 kHz, the first IF is automati-cally shifted up to 455.5 kHz, which may becountered by the software retuning the DDS500 Hz ‘up’. After all, a nominal frequency of12 kHz must be maintained at the output ofthe receiver. The slightly shifted IF will eas-ily fit in the bandpass of the IF filter, allowingus to omit an expensive second oscillator anddesign one around a cheap ceramic resonatortype CSB470. Due to the large capacitancepresented by the oscillator (C15 and C16), theresonator is pulled down 3 kHz with a toler-ance of about 1 kHz.

The IF signal is raised by about 20 dB bya single transistor stage (T2). Overdriving isunlikely to occur because the signal levels arerelatively small due to the slight attenuationby the IF filter and the absence of prestage ormixer gain.

JFET T4 operates as a passive mixer, thatis, a switch for RF signals, being opened andclosed by the 467-kHz local oscillator signal.Besides utter simplicity, the main advantageof a passive FET mixer is its large dynamicrange — signal levels up to 100 mV are han-dled without problems.

DDS tuningThe DDS VFO based on an AD9835 from Ana-log Devices is controlled almost directly fromthe PC’s serial port. An MC1489 RS232receiver chip (IC1) takes care of the swingconversion. Although the DDS clock signal of50 MHz would allow a highest receiver fre-

RF&COMMS


030365-1(C) ELEKTOR

Figure 4. Component mounting plan of the board tested and approved by theElektor design laboratory. The large copper plane allows short ground connections.

The receiver is tuned by a program calledDRM.exe, which makes provision for thereceiver calibration. The inset ‘Step-by-Step’tells you how to start using the receiver.When DRM.exe is first started, it needs to betold which COM port you want to use. Theprogram default is COM1 which may bechanged into COM2, for example. By clickingon ‘Save Setup’ the COM port selection issaved in a file called ‘init.txt’, along with afew other salient parameters for easy retrievalthe next time the program is used. As soon asthe serial connection is successfully estab-lished, the slider (at the top in Figure 6) maybe used to tune the receiver with 1-kHz reso-lution. The arrows at the edges cause 1-kHzsteps, a click in the areas beside the slider, astep of 10 kHz.

CalibrationFrequency calibration is required because thetwo local oscillators in the receiver are sub-ject to a certain tolerance for which no hard-ware adjustments are available. First, thesoftware needs to know the exact frequency ofthe 467-kHz oscillator. Adjust the receiver fre-quency to 0.00 (slider to leftmost position)and start the DRM software. (Note: in the fol-lowing description is it assumed that the pro-gram ‘DRM Software Radio’ from FraunhoferIIS is used — however, it is also possible toemploy ‘Dream’ (see ‘Decoder Software’ inset).No antenna should be connected at thispoint. The spectrum (Figure 7) will show astraight line caused by the first oscillatorbeing tuned to the intermediate frequency.(Note: if the receiver were switched on after

quency of 25 MHz, the output sig-nals near this frequency become tooweak and 24 MHz should beregarded as the absolute limit. Asimple low-pass filter (C5, L1, C6)with a roll-off at about 24 MHz pro-vides sufficient rejection of harmon-ics. Likewise, an additional amplifier,T1, ensures sufficient LO drive forthe mixer.

Analog Devices offers a widerange of DDS integrated circuitsincluding a few with a higher clockfrequency. The AD9835 was chosen

for its relatively low cost and easyavailability (Segor Electronics, GeistElectronics, Barend Hendriksen). Thelow intermediate frequency of455 kHz causes a VFO frequencythat’s only a little above the receivedsignal. The upper limit of the VFOfrequency range is not sharplydefined — the VFO output level willsimply drop gradually above 20 MHzor so. As an aside, this allowed us toreceive the Deutsche Welle DRMbroadcast from Trincomalee, SriLanka, without too much of an effort.

RF&COMMS


Figure 5. The DDS IC (only available in an SMD case) is soldered to the undersideof the board, together with four SMD capacitors.

Figure 6. Windows program DRM.exe for thereceiver tuning in action.

Step-by-stepThe following sequence is suggested when connecting the receiver to a PC.1. Connect the 1:1 RS232 cable to the PC and the receiver.2. Connect the receiver output to the Line input of your soundcard by means of

a screened audio cable.3. Switch on the receiver,4. Launch the DRM software on the PC; select soundcard as target and source.5. Double-click on the loudspeaker symbol in the right-hand bottom corner of

the Windows desktop (or via Programs – Accessories – Entertainment – Vol-ume Control) to open the volume control window (the one with the slidecontrols).

6. Select Properties, then Options and check the box Adjust volume for:Recording.

7. Check the box for the soundcard input you want to use (Line or Microphone)and click OK.

8. In the window that pops up, adjust the volume of the desired input.9. Return to Options – Properties and now select Playback. Disable all inputs

(remove the check mark) except for the one you’re using for the receiver(normally Wave). Use the two slide controls at the left-hand side to controlthe volume on the PC loudspeakers.

10. Launch DRM.exe to tune the receiver to a DRM station.

launching the software, the line does notbecome visible after you’ve moved the slider alittle. If the line still does not appear, thereceiver’s output signal may be too small forthe Line input — change to the microphoneinput and try again. Receiver noise should bejust visible in the lower part of the screen. Pos-sibly, the line falls outside the screen area —adjust the slider until the line appears). Next,the upper slider in the Setup Range has to beadjusted for the line to appear exactly in thecentre of the spectrum. If that is achieved, the

receiver supplies an output signal ofexactly 12 kHz. On our prototype, thesetting was found to correspond to afrequency of 466.4 kHz from whichwe can conclude that the secondoscillator had an error of 600 Hz. Thiserror, then, is compensated by thesoftware offsetting the DDS oscilla-tor by the same amount. The adjust-ment range of the calibration is±2 kHz.

The second step is to eliminatethe error in the DDS clock oscillatorfrequency. The 50.000-MHz quartzcrystal oscillator has a basic toler-ance of ±100 ppm or 100 Hz perMHz, so that a final error of up to5kHz may occur at 50 MHz. Conse-quently, the error would be 1 kHz fora receive frequency of 10 MHz. Thecalibration begins by connecting theantenna to the receiver input andtuning to a strong AM station in theshortwave range (tune using the topslider in DRM.exe). The vast major-ity of SW broadcast stations can beused as frequency standards, their

station frequencies complying withhigh stability standards and a 5-kHzraster. Figure 8 shows the spectrumof an AM transmitter at 6805 kHz.The lower slider has to be adjustedfor the carrier to occur exactly in thecentre.

Theoretically, a this point youwould have to repeat the first cali-bration step, then the second and soon. In practice, that is not necessarybecause the small error in the clockoscillator frequency amounts to nomore than 1% in the IF range. Withan error of 1 kHz at 50 MHz estab-lished, the error at 455 kHz is aninsignificant 10 Hz. The DRM soft-ware we propose to use requires anabsolute accuracy of ‘just’ ±500 Hz.

When you are done calibrating theoscillators, do not forget to save thesetup data to make them quicklyavailable again the next time thereceiver is switched on. By the way,more data is saved, including thecurrent station frequency. Stationbuttons may be linked to your pre-

RF&COMMS


Figure 7. Illustrating IF calibration, here using the program DRM Software Radio (v.2.034).

Figure 8. Using an AM broadcast station carrier as a frequency reference.

Listing 1VB code snippets

Const XTAL = 40000Const IF1 = 454.3

Private Sub output(Data)TXD 0Delay 0.1DTR 1 ‘ CEDelay 0.1BitValue = &H8000&For n = 0 To 15If (Data And BitValue) >0 Then RTS 0 Else RTS 1Delay 0.1TXD 1 ‘ clockDelay 0.1TXD 0Delay 0.1Delay 0.1BitValue = BitValue \ 2

Next nDelay 0.1DTR 0Delay 0.1

End Sub

Private Sub LO(freq)HScroll1.Value = freqLabel1.Caption =

Str$(freq) + “ kHz”Dim frg As LongDim freqLo As LongDim freqHi As LongDim Daten As Longfreq=freq+IF1 ‘add IF1frg=Int(freq/XTAL*

4294967296#)freqHi=frg\&H10000freqLo=frg-freqHi*&H10000freqLoL=freqLo And &HFFfreqLoH freqLo\&H100freqHiL=freqHi And &HFFfreqHiH=freqHi \ &H100output &HF800& ‘Reset‘4 Bytes to FREQ0output(&H3000& + freqLoL) output(&H2100& + freqLoH)output(&H3200& + freqHiL)output(&H2300& + freqHiH)output &H8000& ‘Syncoutput &HC000& ‘Reset end

End Sub

ferred frequencies and they to are saved in thesetup file. The file is editable using a wordprocessor. So, if you (against sound advice)decide to overclock your DDS at 60 MHz, thenew frequencies may be entered here.

Control using Visual BASICThe PC-controlled tuning of the DRM receiveropens a lot of potential, including, forinstance, labelled preselect buttons for yourfavourite stations, or timer-driven tuning tocertain scheduled broadcasts. Moreover, theDDS may be used for measurement purposes.To give all readers maximum freedom in fur-ther experiments, the DDS control isexplained here using a small example. Theuser interface produced by the example pro-gram is shown in Figure 9. The programemploys one slider control, quick tuning but-tons and two boxes for free tuning. Calibra-tion facilities are not provided for the enduser, the calibration being performed by con-stants hidden in the program.

The two decisive procedures of the pro-gram are shown in Listing 1. Using output(Data), 16 bits are shifted into a registerinside the AD9835. The procedure LO com-putes the frequency and the required registercontents of the DDS component. The outputfrequency is adjusted through a 32-bit value,the step size being 50 MHz/232 =0.01164 MHz. The allocation of thee regsistersand their addressing in the upper part of the16-bit control word is detailed in the AD9835datasheet. The program example shows theseven essential register contents needed toactually set the DDS frequency. A frequency‘word’ is divided into four bytes conveyed tofour partial registers.

Near the top of the source code you’ll findtwo constants that have to be adapted toenable te frequency to be calibrated. The nec-essary data are taken from the ready-madeuser program for the receiver. XTAL = 50000stands for the exact clock oscillator frequency,while IF1 = 455 defines the intermediate fre-quency. At a frequency of 466.3 kHz the IFbecomes 466.3 kHz – 12 kHz = 454.3 kHz. Thesoftware controlling the RS232 traffic is a BASmodule already described in [3].

(030365-1)

For further reading:

[1] ‘Digital Radio Mondial’, Elektor ElectronicsDecember 2002.

[2] ‘An Experimental DRM Receiver’, ElektorElectronics December 2003

[3] PC Serial Peripheral Design, parts 1-7, ElektorElectronics September 2000 – March 2001

RF&COMMS


Figure 9. GUI produced by the Visual BASIC example program written for thereceiver tuning and station preselect functions.

Decoder softwareIn addition to the tuning program DRM.exe (supplied by Elektor on disk or as aFree Download) you will require DRM demodulation/decoding software thatworks in combination with your PC soundcard. Two products are available on themarket.

DRM Software Radio produced by the German Fraunhofer IIS (currently ver-sion 2.034) may be obtained at a cost of 60 Euros (approx. £43) from an onlineshop facility at www.drmrx.org. Payment for your order is by credit card. Thedownload information and a software key arrive by email. The latest version sup-ports the new MP4-based DRM standard introduced on 15 December 2003.Nearly all DRM stations now broadcast in stereo and achieve excellent soundquality using the new format.

The DREAM open-source project from Volkert Fischer and Alexander Kurpiers(a former Elektor author) of the Darmstadt University Institute for Communica-tions Technology is currently available as version 1.0. The program is only sup-plied in the form of a C++ source code file because the authors have employedthird-party modules that have to be obtained from the respective owners. TheDREAM code itself may be found at

http://sourceforge.net/projects/drm/

The project may be compiled for Windows as well as Linux. If you are less thanconversant with a C++ compiler, ask around for assistance with the creation ofthe files. DREAM_V1.0 has evolved into a serious alternative to the DRM Soft-ware Radio package. The program is stable and now presents less of a CPU loadthan before. Meanwhile, the reception of pictures has become possible and the program isalso capable of writing a log file containing reception reports. DREAM is very tol-erant in respect of the exact frequency of the DRM baseband and will faithfullyscan the complete range from 0 to 24 kHz. AM reception has been added as anextra mode, allowing the DRM receiver to be used for classic broadcast receptionon the long- medium and shortwave bands.

In a future issue we will return to the DRM software decoder in greater detail.The DRM programs mentioned above are compatible with Windows 98 and up(i.e., 98, 2000, NT and XP).

drm receiver 9835-1

Documents