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Reuter RDR52

 

In September 2021 the rumor went around in the hobby scene that the company Reuter Elektronik launched a new receiver. Of course I asked Mr. Reuter, what was behind the rumor. Indeed he confirmed to me the development of the RDR52! This new receiver is based on the RDR51 Pocket, the portable receiver which is very popular with lovers of noble reception technology. The RDR52 also has a 4.3" touch screen like the Pocket. Also most of the functions of the Pocket are included in the RDR52. Roughly speaking, the RDR52 is the desktop version of the RDR51 Pocket.

Of course, the RDR52 has a much larger case than the Pocket. But not as big as you might think! On the pictures it looks like a full-grown table receiver. But this is deceptive! It is just 189x108x105 mm (WxHxD). So it is a very compact desktop receiver. One of the highlights of this receiver is the silky smooth tuning knob. This sits on the shaft of a high-precision optical encoder from Megatron. You can also find encoders from this company at Rhode & Schwarz. A very practical feature is the detented volume control, which is equipped with a push function. So you can quickly switch between the volume control of the loudspeakers and the headphones with a short press. The housing is as usual from Reuter Elektronik, perfectly processed and is completely made of black anodized aluminum. To achieve a good RF shielding, the contact surfaces of the individual housing parts were additionally milled. Qualitatively and HF-technically, a table housing can not be manufactured better!

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The main features of the RDR52 C2/C5

-- Frequency range: 0KHz - 30 MHz, 50 - 71 MHz, 87 MHz - 110 MHz, 130 - 156 MHz, 174 - 240 MHz (DAB+ reception only)
-- Bandwidth filter: 10Hz - 20KHz in 40Hz steps freely adjustable. Dependent on audio resolution.
-- Frequency based modes: Sync - DSB - LSB - USB - EUSB - SBCW - CW
-- Operating modes Time based: AM-E - FMN - FMW - USBQ - LSBQ - DIGI - DSBQ
-- Tuning step sizes: Arbitrarily adjustable from 0.5Hz - 999.999.5KHz / direct selection of preprogrammed step sizes
-- Spectrum viewing widths: Smallest viewing width: 6.2KHz, largest viewing width: 52MHz (option)
-- Module C2 built-in (FM&DAB+)
-- Module C5 built-in (HiFi-DAC - Line-Out)
-- FM mono/stereo with wide function and RDS
-- FM filters: 38KHz-S, 50KHz-S, 80KHz-S, 80KHz-HQ, , 120KHz-S, 120KHz-HQ, 240KHz-HQ, 300KHz-HQ (S= Steep filter slopes, HQ= Flatter filter slopes for optimal    listening pleasure). Partial option.
-- DAB+ reception in mono or stereo
-- Frequency deviation internal oscillator: < ±5 ppm after 10 min., internal manual calibration with active GPS with min. 7 satellites: < ±1Hz.
-- Memory locations: 199 station memories, 28 for undo function.
-- Passband tuning
-- Auto-Notch & manually adjustable notch filter
-- Noise Blanker
-- DNR (Digital Noise Reduction)
-- AGC: rise and hold time adjustable
-- 2x 16bit ADC
-- Real time spectrum and waterfall
-- Fast and very bright resistive touch screen with 4.3" (109 mm) diagonal, WVGA 800 x 480 pixel resolution
-- GPS module for frequency calibration and indication of altitude above sea level, coordinates and time in UTC.
-- WLAN module for wireless firmware updates & screenshot functions
-- Bluetooth module for connection of wireless speakers or headphones
-- Bandpass filter for LMK (1-10MHz, 10-30MHz) or bypass
-- Bandpass filter for the 6m range (50 - 70MHz)
-- VHF bandpass filter (87 - 110MHz)
-- 2m bandpass filter (130 - 156MHz)
-- Bandpass filter for the DAB+ range (174 - 240MHz)
-- 8 GB flash memory for audio recordings
-- BNC connectors for LMK, FM & DAB+ reception
-- SMA connectors for GPS & WLAN/Bluetooth antenna
-- 5,5x2,5mm hollow plug socket for power supply
-- Power supply: 9 V ... 14.5 V DC max. 0.8 A
-- 3.5mm jack sockets for headphones/speakers, microphone & morse key (with built-in transmitter)
-- 2 built-in speakers for stereo playback
-- Dimensions: 189x108x105 mm (WxHxD)
-- Weight: max. approx. 0.8 kg, depending on variant / equipment

Included accessories:
-- Touch input pen
-- GPS antenna with 3m cable
-- WLAN/Bluetooth antenna

Block diagram of the RDR52

Variants of the RDR52

The RDR52 is available in different equipment variants. The accessories can be ordered ready installed, or after the purchase to install yourself. With the hardware accessories appropriate holes must be drilled on the back of the device. With software extensions only an unlock code which is firmly connected with the serial number of the equipment must be entered.
 

RDR52 C1
0 - 30 MHz, 50 - 71 MHz, 2x 16 Bit ADC (Simple tuning knobs) >Standard version without accessories<

RDR52 C2
Like RDR52 C1, additionally with module C2 (FM / 2 m / DAB+)

RDR52 C3
Same as RDR52 C1, additionally with module C3 (11 band / 5 W transmitter 160 m - 6 m)

RDR52 C4
Same as RDR52 C1, additionally with module C4 (exciter 10 mW 100 kHz - 156 MHz)

RDR52 C5
As RDR52 C1, additionally with module C5 (HiFi-DAC 106 dB SNR, Line-Out 3.5 mm jack)

Modules C3 , C4 or C5 can only be used separately and not together (same slot)
If the RDR52 is ordered with one of the options listed above (except C1), high quality tuning knobs will be mounted to the unit.

*Special option "Metal" with stainless steel tuning knobs and loudspeaker with aluminum diaphragms. For all versions against surcharge*.

Software options:
Special equipment "wideband spectrum" - extension of the displayable spectrum range up to a maximum of 52.6 MHz width (depending
of the switched on frequency range).

Special equipment "High-End FM" - 4 additional filters for the FM range with especially high selectivity and stereo reception with the
highest possible quality.

 

 

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A look under the hood of the RDR52

The view inside a digital receiver is admittedly not very exciting. Because of the receiving power, which is close to professional devices, one would hardly suspect an almost empty housing! The secret lies in the operation of the RDR52. This differs fundamentally from the usual direct sampling SDR's. On the middle picture, lying on the device, you can see the built-in options "HiFi-DAC Line-Out" and the "FM/DAB+ Module.
 

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Preparations before the RDR52 arrives

The first thing to consider after ordering the RDR52 is the power supply for the unit. The RDR52 has instrument quality and should get a clean and interference free power supply. A good quality stabilized transformer power supply would be just right. Also switching power supplies can be used. But you should be sure that they are clean and interference free. It is sad but true, many SWL's with partly very expensive receivers, neglect the topic of clean power supply and then wonder about (self-generated) interference. Before the RDR52 is handed over by the parcel carrier, a DC cable with a 5.5x2.5mm hollow plug should be ready. Because the DC cable (power supply cable) is unfortunately not in the scope of supply!

The operation of the RDR52

For me as a Reuter equipment connoisseur, the operation is no hurdle, because all Reuter receivers have largely the same operating philosophy. Apart from model-specific functions. The RDR52 should ideally be placed on a non-slip surface because it is a lightweight of about 800g. With almost every touch, it slips away a bit. The device is first brought into working position. If you like, the two feet can be folded out. If the RDR52 stands directly on the table, this improves the operation and the top view of the display. Working with the RDR52 is less fiddly than with the Pocket. The touch display is the same size, but there is a large tuning and volume knob with a push function. This allows a more relaxed work than with the Pocket. Due to the display size of the RDR52 and increasing age, the typing areas on the display seem to get smaller and smaller! RDR52 owners in advanced age, often need reading glasses to decipher the sometimes very small fonts of various functions on the display. The operation is usually done with the touch stylus. You have to be very accurate to hit the right spot on the display. But fortunately, this is also a matter of getting used to. After a short time, you work fluidly with the RDR52 and are pleased with the enormous reception performance of this dwarf.

The device offers a lot of functions and has a somewhat different operating logic than the usual receivers. I recommend newcomers to deal in advance with the manual to have an easier entry into the RDR52 world.

The RDR52 in use

In the autumn DX-Camp 2021 in Solingen I was allowed to test the prototype of the RDR52 for the first time. Reuter Elektronik made the device available to me for the few days. It was not only tested by me. Everyone, who participated in the DX-Camp, had the possibility to work with the RDR52 prototype. The advantage of such an action is, it weak points at the equipment and errors in the software are uncovered. Also wishes were expressed. From this the module "DAC Line-Out" was developed.


 

The reception on VLF, LW, MW and SW

The main discipline of the RDR52 is the reception of very low frequencies of the VLF range, long wave, medium wave, short wave and the 6m amateur band. At the DX-Camp the RDR52 was operated on antennas with strong reception. These were a 250m long Beverage for USA medium wave reception, an end fed long wire with over 100m length, as well as various active antennas. Among them was the NTi MegaDipol MD300DX, which delivered very strong signals. Such antennas are a real challenge for the receiving technology. Not only for the receivers, but also for the antenna distribution system, which often reached its limits. In the evening hours, when the sum signals became stronger, the antenna distribution system regularly overloaded. In certain frequency ranges, all kinds of ghost stations appeared. This is not suitable for equipment tests. To get realistic values, I had to disconnect my receiving equipment from the distribution system and go directly to the antennas. Besides the RDR52, I had the Winradio G33DDC and the new Elad FDM-S3 with custom bandpass filter for "General Coverage" reception from Ernst Kirschbaum (DL2EBV). Both PC-bound SDR's are 16bit premium receivers and strong competitors for the RDR52.
On the DX-Camp we had so to speak 24h operation. It was practically around the clock, radio stations from all over the world received. Of course, the RDR52 was used and constantly compared with the two opponents. With the active dipole NTi MegaDipol could be taken up particularly in the VLF range, a few exotic transmitters from the noise. The time signal stations JJY40 from Japan on 40KHz and BPC from China on 68,5KHz could be picked up almost every evening/night. Reception-wise the three receivers hardly differed from each other. The RDR52 was slightly less noisy than the other two SDR's and made listening a bit more pleasant. In the VLF range no major signal problems could be detected.
On the long wave the usual stations could be received with all three receivers without problems. Among them also Iceland on 189KHz, 207KHz and Ireland on 252KHz. This succeeded again with the MegaDipol best. The RDR52 in the mode "SYNCH" brought the transmitters best. Quiet and low noise. With the switching on of the Surround mode, the audio got a stereo effect and sounded thereby still somewhat more clearly.
Above the long wave there are many radio beacons, called "NDB" Non -Directional Beacon. With many SWL's a popular field of activity. These "NDB's" sometimes transmit very close to each other, which makes identification difficult. In this particular case, the RDR52 couldn't quite keep up with the PC-bound SDR's. Reception-wise it could, but when it came to visually separating the transmitters on the spectrum/waterfall, the RDR52 reached its limits. For this the display is too small and the resolution with 10Hz a bit too coarse.
On the medium wave one could use the 250m long Beverage antenna. This was aligned towards North America. In the early morning hours, medium wave stations from the USA, Cuba and Puerto Rico could be received. But unfortunately only a few. The propagation conditions were not good. But the RDR52 handled it just as well as the PC-bound SDR's. Selectivity, sensitivity and intelligibility of weakest signals were excellent.
Shortwave offers a myriad of signals and reception possibilities. Whether listening normally to international broadcasting in the many languages, doing hardcore DX, decoding digital stations, listening to airband radio or ham radio, or listening to the mysterious number stations.... For shortwave reception I used the 100m long wire, the MegaDipole and the usual camp loops equipped with Stampfl Bluewave plus amplifiers. I made countless reception comparisons with the RDR52. From normal broadcasting to hardcore DX, receiving distant stations on the turf. The RDR52 handled all tasks without a hitch and even outperformed the other two competitors by a small margin. With its low noise reception, it was often more pleasant when listening to very weak stations for longer periods of time. No large signal effects could be detected, although the frequency display occasionally lit up red. A sign that the ADC was clipping. That was always in the evening hours where the signal levels increased. But also with the G33DDC the clipping ADC indicator lit up from time to time. However less than with the RDR52. The Elad S3 with its new bandpass filters was unimpressed by the high signal levels.

Shortwave reception of Voice of Greece

The test at home

The differences from the prototype to the production unit were only small things in the software and the housing, which did not affect the reception. At the beginning of January 2022 I received my RDR52. Since then, I deal with the device almost daily and was able to gain a lot of experience with it. At home the reception conditions are not like at the DX camp. From the neighborhood come occasionally strong disturbances, which affect the reception negatively. But also at home the RDR52 plays convincingly. The noise blanker suppresses the pasture fences very well. The noise reduction (NR) almost leads a shadowy existence here, because the RDR52 already has very little noise by itself. If the noise interference increases, the NR can do a very good job and reduces the noise. However, the NR must not be turned up too far. max. to level 5 for audio reception. Above this level digital artifacts can be heard. On long, medium and short wave the results are again convincing. The synchronous detector of the RDR52 also contributes to this. This is always switched on in the operating mode "SYNCH". The sidebands can be changed of course. It is simply noticeable again and again, how noise-poor the RDR52 is. The reception in SSB is clearly quieter than with the comparison devices. As an example the Volmet station "Bangkok Volmet" on 8743KHz was one of the cream pieces. Virtually noise free and perfect audio at 3KHz bandwidth.

The Time Based modes like AM-E offer a higher audio quality, comparable to a tube radio, which sounds round and full. On the other hand, these modes have a limited range of functions. If the reception is undisturbed, these modes are recommended. AM stations can then be heard in "AM-E". The bandwidth filters have flatter filter edges and sound much more pleasant and analog. There are also separate demodualtors for the sidebands (LSBQ & USBQ).

During testing, it was noticed that the WiFi/Bluetooth module causes interference in the SW reception as soon as it is switched on. The interference can be heard around 15545KHz and can be seen on the spectrum. Other frequencies are also affected, but mostly the interference peak is below the band noise.
 

Spec-Based
Time-Based


The RDR52 also receives FM (time-based) and DAB+ with the optional add-on module. According to Reuter Elektronik, DAB+ is rather to be considered an add-on. The FM receiver cable is housed separately on a pluggable circuit board in the device, together with the DAB+ receiver section. For FM reception, I used a replica of the well-known Dressler ARA2000 active antenna. This receives from 25MHz to about 2GHz. This antenna was built by Heinz Stampfl (HB9KOC) and me. Heinz built the broadband amplifier and I built the actual antenna. The combination RDR52 with the Stampfl/Fenu antenna harmonize very well. The levels are not excessive and the noise of the amplifier is low. I could not observe any overload effects or ghost stations. The RDR52 offers some interesting features that should convince even FM DXers. Separation sharp and HQ bandwidth filters for each reception situation. RDS with fast decoding and detailed information about the station. Furthermore, in addition to stereo reception, a stereo wide function is built in, with which the stereo width can be continuously adjusted.


FM reception with MPX , pilot tone display and display of detailed RDS information.
 

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Then there is the DAB+ reception. Reuter Elektronik is so far the only company that combines a shortwave receiver with a DAB+ receiver. However, you can't compare this DAB+ receiver with a conventional DAB+ radio. The operation of this option takes some getting used to. If you want to listen to DAB+, you have to start a scan every time you start the device. This takes a good minute, depending on the number of stations found. After the scan, all stations are listed. Even those that do not provide audio. If you then tap on a listed station with the stylus, playback starts if the signal is strong enough. The higher the bit rate, the better the audio quality. Individual DAB+ stations can also be stored in the station memory, where the KW frequencies etc. are also stored. As mentioned above, the RDR52 is not a normal DAB+ radio. If one switches the equipment off and again on and wants to call then the stored DAB+ transmitter, always a complete transmitter search run is released. Thus one waits again a long minute, until the equipment accomplished the search run. A cumbersome thing! However, the audio quality makes up for it when listening with headphones! The DAB+ function not only brings audio, it also displays pictures, names of the artist, and so on.

DAB+ Sender list

 

The audio quality of the RDR52

The RDR52 has two built-in full-range speakers from Visaton. These tiny 3.2cm diameter speakers provide a sufficiently pleasant sound with a few sacrifices that are unavoidable due to the size of the device. For shortwave reception the sound is good. For music playback on FM or DAB+ reception, the bass range is almost completely missing, which is a pity! With the connection of an active speaker, such as the Bose Soundlink Mini 2, the playback gets the necessary bass! External speakers or headphones can also be connected to the RDR52 via Bluetooth. The audio quality is good enough for connection to a HiFi system.

Other functions

TheRDR52 has a great many features. To try to cover them all in a detailed review would go beyond the scope. Below are the most important functions and settings. For details I recommend to download the manual.
When you tap the menu button, a gray bar appears on the right side of the display, which in turn leads to buttons for various functions and settings. The following pictures show the most important settings of the RDR52.

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Conclusion

The RDR52 is an ingenious semi-professional receiver and goes beyond. It simply offers everything the dedicated listener could want. The RDR52 offers long, medium, and shortwave reception at a very high level and is a challenge to the premium class of PC-linked SDR's. The comparison devices could not top the RDR52. Very good, almost audiophile FM reception with selective bandwidth filters & DX capability and of course DAB+, top it all off! DAB+ also sounds good, but can't quite convince because of the awkward operation.
The inactive bar displays at the top right of the display are unattractive. These are primarily intended for the transmitter functions. This fabulous receiver would have deserved an independent interface!

Wishes? Definitely. What is noticeable after working with the RDR52 for a while are the very small typing areas and fonts, which are almost invisible to the naked eye. The manufacturer should think about a simplified user interface here.
The other wish is the control of the RDR52 from a computer. According to Reuter Elektronik, this should be realized soon. Also the program codes are to be opened as "open source".

Worth mentioning is the reaction time of the manufacturer, should one have a problem with the device or software. Mr. Reuter reacts within a day and takes the customer seriously. Software updates come regularly and customer requests are very often implemented.

After long tests, comparisons and experiences on the DX-Camp and at home I can say only one thing: absolute top class!

Posted: 26.05.2022
 

 

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