Dean Bianco user guest review of the Reuter RDR55E.
The
RDR-55E is a high-end, stand-alone SDR receiver (can be used as a QRP
transceiver as an option, not available in the review radio) covering a
frequency range of 1-30 MHz and, in the review unit, 50-54 MHz.
The FM Broadcast Band and the 2 Meter Ham Band (87.5-108 MHz and
144-148 MHz, respectively) are available as options, not available in
the review radio. The receiver is built in small batches by the
German firm of Reuter Elektronik, led by the electronic engineer and
fabricator, Burkhard Reuter. This stand-alone model is ideal for
those users who prefer not having to engage a computer, monitor,
keyboard, and mouse as is normally the case for many SDR's. Employs a touch-screen panel to access all of the tuning
parameters. Only one large weighted knob.
The following is an overview of the test sample I own:
Test Model: RDR55E2 firmware version EV 631
Serial Number: 085
Build Date: November 2021
Dimensions:
(W) 11.42 in x (D) 9.65 in x (H) 5.91
in-----(W) 290 mm x (D) 245 mm x (H) 150 mm
Weight: Varies depending the number of modules installed. Test unit weighs approximately 12 lbs (5.44 kgs)
Operational Theory: Proprietary time-based and spectrum-based, direct-conversion processing scheme.
Receiver Case: A
heavy-gauge main frame chassis with a bus board that employs up to 9
rear-mounted pluggable modules, depending on options.
Case Materials:
Anodized, extruded aluminum top and bottom covers. 0.2-inch
machine milled side panels. Rear panel contains plug-in modules
for various functions and options. The modules are constructed of
heavy-gauge aluminum. Rubberized tip-up feet. The radio can be
built to your choice of black or grey powder-coated color.
Display: TFT WVGA 5-inch
diagonally-measured, 512 colors, fully adjustable brightness. Takes
very little finger pressure to activate.
Digital Architecture: (for tested unit) 2 x ADC's in push-pull 17-bit, Cyclone V FPGA, direct digital conversion.
Modules: (as installed in test
sample):
RPS30D-- 110/230 volt 25 VA consumed, no cooling fan
used in test sample.
RAD17D-- A/D converter, RF deck.
RDR35D-- DSP software,
GPS-disciplined oscillator, WI-FI for WLAN.
FDA21-- Audio
Card.
All modules are heavy-gauge anodized aluminum.
Input Connectors:
- SMA for receive antennas
- SMA for GPS antenna.
Radio comes with an
SMA-to-BNC coax jumper cable, touch-screen stylus, GPS antenna with
coax cable (if GPS option is installed), Wi Fi antenna.
Tuning Encoder:
High-quality steel rotary optical encoder w/ finger dimple, smooth
tuning w/ no detents. Optional magnetic encoder w/detent tuning
(not tested).
Power
Requirements: Choice of either a built-in 110/230 volt
switching-mode power supply, which uses <25 va in full operation,
<1 va in standby, or a user-supplied 13.8 volt external power supply.
Features:
Adjustable Tuning
Steps: Any step from 0.5 Hz to 100 Khz via the keypad, or in
fixed steps from 1Hz, 10 Hz, 100 Hz, 1 kHz, 4.5 kHz, 5 kHz, 8.33 kHz, 9
kHz, 10 kHz, 12.5 kHz, 25 kHz, 50 kHz, and 100 kHz for all modes.
Frequency display reads
out to the nearest 1/2 Hertz (yes 0.5 hertz !) Main oscillator stability +/- 1
ppm. GPS option stability is exactly 1 Hz (tested).
Adjustable variable speed tuning, defeatable.
Modes spectrum-based: SYNC (w/selectable sidebands or DSB), USB, LSB, DSB w/o carrier, CW.
Modes time-based:
AM-Envelope, FM-N, FM-W, DIGI (optimized settings for user-supplied
modem decoding of digital modes), analogue-emulating DSBQ, LSBQ, USBQ
for when extremely low latency, constant group delay, lowest distortion
are required and/or fed to a PC sound card or speaker.
Variable bandwidths from 40 Hz to 20.32 kHz, mode-dependent:
Selectable bandwidths by mode:
AM-Envelope---from 3 kHz to 20 kHz---in progressive 500 Hz/1 khz/2 kHz
increments.
AM Synchronous DSB---from 80 Hz to 20.32 kHz---in 80 Hz increments.
AM Synchronous LSB/USB---from 80 Hz to 10.24 kHz---in 80 Hz increments.
DSB (no carrier)---from 80 Hz to 20.32 kHz---in 80 Hz increments.
LSB/USB---from 80 Hz to 15 kHz---in 40 Hz increments.
CW---from 80 Hz to 1.6 kHz---in 40 Hz increments based on a pitch
setting of 800 Hz.
(Bandwidth
increments differ dependent on a pitch setting other than 800 Hz which were
untested)
USBQ/LSBQ---from 1.5 kHz to 10 kHz---in progressive 250 Hz/500 Hz/1 kHz
increments.
DSBQ---from 3 kHz to 20 kHz---in progressive 500/1 kHz/2 kHz increments.
FM/W---fixed steps of 38/50/60/80/120/250/300 kHz.
FM/N---from 3 kHz to 20 kHz in progressive 500 Hz/1 kHz/2kHz increments.
DIGI---from 125 Hz to 4 kHz in progressive 250 Hz/1 kHz/2 kHz
increments.
Adjustable:
- PBT in all modes except time-based.
- Notch filter in all modes except time-based.
- Dynamic noise reduction in all modes except time-based.
- Two-step noise blanker in all modes except time-based.
- RF squelch threshold, all modes.
- AGC limit, AGC hold and AGC attack constants in all modes.
- Audio filtering from 20 Hz to 15 kHz continuously.
- Selectable surround-sound feature aids in weak-signal audio recovery.
- Spectrum display with variable refresh speeds, adjustable dBm increments.
- Waterfall display, 16 colors. (Untested)
- 199 memories. (Untested)
- 20 dB attenuator, nominally. Works in concert with the RF preamp to adjust attenuation level.
- RF Preamp 15dB
- Built-in preselector/RF filters. Adjustable. Defeatable.
- Built-in, front-firing speaker 2 watts output. External speaker(s) can be effectively fed from the headphones jack.
- Front-mounted 1/8 inch headphone jack.
- Independent controls for the speaker and headphones audio.
- S-Meter reads in dBm, dBu, and S-units and features separate peak-signal readings.
- Optional GPS module
which calibrates the frequency stability continuously to 1 Hz accuracy,
displays time in UTC, displays longitude and latitude, altitude above
sea level, satellite ID and SN/R, and receiver clock deviation in Hz.
(Tested)
OBSERVATIONS:
The following was based
on my personally-owned RDR-55E fed by a 122-foot long T2FD antenna with
the high point 50 feet above ground, fed with quality RG-8U coax cable,
no signal processing accessories, in a quiet rural receiving post.
OVERALL AUDIO:
Superb audio, especially with an external speaker(s). Rich
fidelity benefits strong and moderate signal levels, yet pleasingly
very effective in aiding weak-signal recovery, to my ears.
Enhanced signal recovery when judicious use of PBT, AGC, and DNR are
engaged. I use Bose Companion 2 Series III speakers with excellent
results. The audio quality exceeds that of my WJ-8711A. The
lower distortion is noticeable. I formerly owned a Flex 6400M
transceiver which had excellent to superb audio, but the RDR-55E is
better still. The bass frequencies are smooth and warm sounding,
never muddy (unless using a very narrow bandwidth, of course).
The mid-range and treble is crisp enough. I prefer a wide range
in audio recovery, and if you use a quality external speaker, you can
appreciate the subtle differences of the highly customizable audio
frequency range. I notice less of a "digital sound' to the
overall audio in most bandwidths as compared to other DSP-based
receivers. However, for those times when a clear signal is
present, there is a time-based demodulator that produces a
near-tube-type audio experience with AM and SSB.
PASS BAND TUNING:
Available in all modes (except time-based) and it works well.
Works superbly to avoid adjacent-frequency interference and for tone
contouring. No digital artifacts or circuit whine when adjusting
the settings, as is the case in many modern receivers.
RF BANDWIDTH
SELECTIVITY: A plus for the RDR-55E over most receivers---SDR or
otherwise---is the very wide bandwidth filtering. It ranges,
depending on the mode in use, from 80 Hz to 20.32 kHz, fully adjustable
in 40 Hz steps via the main rotary encoder, all done in a seamlessly
smooth and fast maneuver. Theses widths, however, are mode
dependent. For instance, when tuned to a station in lower or
upper SYNC mode, the widest bandwidth is slightly over 10 kHz
wide. Not a complaint as this makes sense as the effect is the
same as when DSB SYNC is set to 20kHz. LSB and USB tune out to 10
kHz maximum and CW goes out 1.6 kHz maximum. While I have no test
equipment in my listening post, I can only go by what my ears tell
me: the selectivity of these DSP filters are razor sharp and are
the equal of the WJ-8711A, known for its sharp filter shapes. If
softer audio emulating analog sound is desired to reduce digital
latency for critical digital or SSB use, you can switch from standard
spectrum-based demodulation to time-based demodulation in AM, LSB/USB,
DSB, or DIGI modes where less brute-force filter shape is not desired
or required. Another plus is the lack of noticeable ringing in
narrowest of CW filters, to my ears.
SENSITIVITY:
Again, I go by my ears as I do not have any test equipment, but the
RDR-55E's sensitivity is not an issue at all. I compared the
sensitivity to the WJ and to an NRD-515, known for its high
sensitivity. All three receivers were equal in signal strengths
at the weakest levels. I did my best not to allow audio recovery
to influence the results. All three were equal with no
discernible winner. However, I had to turn off the Reuter's
built-in preselector on frequencies above approximately 17 MHz in order
to amp up more sensitivity lost by having the pre-selector
engaged. The 8711A has a
pre-selector, but it had no loss of sensitivity whether engaged or not
at these higher HF frequencies, unlike the noticeable difference with
the Reuter. But I should emphasize that this was a very small
difference, and of course these were tested with very weak signals.
SYNCHRONOUS
DETECTION: Whether used in the DSB mode, or the LSB/USB
selectable mode, fading-distortion in the audio recovery is completely
vanquished. Its ability to maintain lock on rapid, deep fades and
on weak signal carriers is superb. When used in the
selectable-sideband mode, adjacent interference was reduced or
eliminated on several test stations. This is a true winner.
It compares favorably to the old Sherwood SE-3 in terms of audio
quality, shaping, and interference rejection. It very slightly
outperforms the Flex6400M when it comes to AGC smoothing of rapid
fades, and that radio has a damn good sync detector. The WJ has a
worthy sync detector, but it is only DSB, not sideband-selectable, and
that is a considerable drawback when conditions call for adjacent
channel interference reduction. Also, the WJ's sync can
occasionally lose lock. I also had at one time the superb ICOM
R-8600 and its native sync detector, in my findings, is a real dog, so
no fair comparison there. I have yet to find a signal that
has made the Reuter's sync lose lock! It's the best I have
experienced so far and neck-and-neck with the Sherwood SE-3.
SPECTRUM SCOPE:
The 5-inch diagonally measured spectrum scope is well-designed, crisp
and uncluttered in appearance. I have mine set to 160 kHz
end-to-end bandwidth and set so that the speed of the real-time
spectral signal lines are moderately smooth in action, although these
parameters are adjustable to your taste and requirements. By
choice, I have very simple requirements for my spectrum display.
I merely use the display to see adjacent signals near my target signal,
and select a signal blip and tune in that way. Others may prefer
deeper analysis of signal modulation peaks and other such data.
Even though I have not much need for the spectrum display other than
what I describe above, no doubt many of you will love the great detail
of signal analysis provided by this top-notch spectrum display.
NOTE: The RDR-55E features a 16 color, full-featured waterfall
display. It cannot be run concurrently with the spectral display,
as designed by the manufacturer. I did not test the waterfall as
I have no interest in it. The display, when I observed it briefly
to make sure it works, appeared to be adequate.
STRONG-SIGNAL
HANDLING: The dynamic range seems to be very robust. I have
yet to find any intermodulation, cross-modulation or strong-signal
overloading, with or without the 15 dB pre-amp engaged. I tested
it against a 75 db over S9 (+ 5 dBm!!) medium wave signal from a
temporary location 2 miles from at 10 kW of power. No attenuation
engaged. Not a blemish in reception quality to my ears. I
was blown away by this. My WJ has a great dynamic range with
strong signal levels, but at +5 dBm the WJ showed some noise
artifacts. Impressive! Unlike other SDR's, such as the
high-quality super-performing ICOM R-8600, the RDR-55E has no overload
indicator. Perhaps because it doesn't need one.
PHASE NOISE:
According to the manufacturer's specifications and the WRTH's test
equipment, the phase noise is purported to be better than -140
dBm. My ears tell me that extremely weak signals adjacent to very
strong ones do not get "de-sensed" by the stronger signal's
presence. The RDR-55E has the quietest apparent noise floor than
any other high-end receiver I have owned, namely the WJ-8711A, the
R-390A and the NRD-515. I had barely-usable audio recovery from
the BBC on 9410 kHz at a very low signal strength of -134 dBm with the
Reuter whereas the WJ was slightly less useable and the NRD produced
only mud. Impressive.
AGC: The AGC is
very flexible in terms of hang-time, attack-time, and limit
settings. Unlike many receivers, the RDR-55E requires one to make
frequent adjustments in order to obtain the best audio recovery under
all kinds of reception conditions be they easy-listening or rife with
fluttery, atmospherically-noisy, or interfered-with signals. This
cannot be understated. A long AGC hang-time can smooth out most
if not all of the fluttery signals one encounters from signals affected
by solar activity and by polar path absorption. Sometimes a short
hang-time reduces the effects of audio drops on those stations which
have low modulation. We also have adjustable AGC attack-time
settings. The RDR-55E's is highly effective in reducing pumping
and eliminating syllable-onset popping or clipping distortion that is
the bane of radio hobbyists who use receivers with poorly-engineered
AGC circuitry. Also, judicious adjustment of the attack setting
can tame background static crashes, man-made transmitter splatter, and
an aggressive ionosphere. This is not a "one-size-fits-all" or
"set-and-forget" AGC. I for one love this level of
adjustability, but your preferences may differ. Keep this in mind
if you are thinking of obtaining an RDR-55E.
NOISE BLANKER:
This is the thorn in the rose that is the RDR-55E. It simply does
not work. At ALL!!! Inexcusable on a state-of-the-art,
DSP-based communications receiver. It should be noted that I have
spent hours adjusting all of the settings, in combination with other
reception aids such as PBT, DNR, AGC, etc in order to get it to blank
any pulse-type noise that it is designed to reduce or eliminate.
My hours proved fruitless. Now, in all fairness, when I contacted
a Reuter associate, he informed me that the reason for my finding the
NB function inoperable might have to do with my North American 60 Hz
line frequency vs the 50 Hz line frequency found in Europe and in much
of the rest of the world. I was told that Mr Reuter would be made
aware of the issue and that it would be a matter of a firmware update
to resolve the issue. I for one cannot wait until that
happens. If and when it does, I will amend this review.
DYNAMIC NOISE
REDUCTION: If the NB is the Achilles heel of this radio, the DNR
function is the icing on its cake! The effect is excellent in
reducing white noise from the audio path. Voice and music equally
are rendered very natural even when the DNR is set to a well-advanced
level. The only time digital watery effects come into play are
when the setting is up to its second-to-last and highest reduction
strength. I found the last setting only useful on those occasions
where the quality of the audio is secondary to the need to recover
intelligibility under harsh noise conditions. Particularly
satisfying is its ability to reduce by leaps and bounds the tiring hiss
of white noise from weak-to-moderate signals. I found it reduces
the edge of crackly static crashes adequately. Overall, it's
flawless.
ATTENUATOR AND
PRE-AMP: We have 0 db, 5 dB, and 20 dB settings of selectable
attenuation from which to choose. We also have a selectable 15 dB
preamp at our disposable. Although I could not find ANY occasions
where the attenuator was needed, I like to reduce the noise floor and
signal intensity of the MW band at night. Unlike some pre-amps on
other radios, it does not cause any signal overloading, cross-mod or
other weird behaviors.
RF THRESHOLD
(SQUELCH): Adjustable in dBm increments. This generally works
quite well and in all modes. It does however have a flaw, in my
observation. In some circumstances, the initial signal rise that
breaks the silence of an engaged squelch cuts off a second or two of
the content of that signal. Yes, I was mindful of all the
settings and adjusted all variables continuously, but to no
avail. Again, not under all circumstances. Oh well.
It's not really that big of a deal to me---but it may be to you.
On the plus side, when signals fade below the RF threshold setting, the
hysteresis effect allows a temporary suspension of the absolute
threshold setting so that the audio allowed to pass doesn't get chopped
up and deleted during a fading signal as it gets under the threshold
barrier. Nice! The squelch on the WJ is also superb, but it
lacks hysteresis. The only squelch I have used that overall is
better implemented is the one on the ICOM R-8600.
BUILT-IN SPEAKER:
The speaker produces a high audio range and is adequate under many
circumstances. My last SDR radio was the Flex6400M which also
features a built-in speaker. It was an absolute joke. Weak,
thin audio that requires the speaker volume to be turned up to more
than 3/4 of the way. Thankfully, nothing at all like that with
the Reuter's built-in speaker. However, as good as it is, it is
not stellar for my taste. As such, I use Bose amplified speakers
to allow the rich and powerful audio to shine through that the
RDR-55E is capable of producing.
HEADPHONE USE:
High-impedance headphones allow ample volume without hum or buzzies or
other audio weirdness to come through. Other radios usually have
some deficiencies in headphone-delivered audio. Not so with the
Reuter. Excellent. I use quality Sennheiser phones for best
fidelity.
MAIN TUNING-ENCODER
KNOB: The knob is made of quality, weighted steel and contains a
finger indent for super smooth tuning. It never binds, never
slops over. The action is consistent whether you are slowly fine
tuning a signal in or rapidly tuning across a band. There is a
variable rate tuning setting that can be set to various levels of
speed-increases the faster you tune the knob. This feature is
offered or in the past had been offered with other receivers, with
varying success. This is my first time having a radio that offers
it. I personally love it as it reduces user fatigue when doing a
lot of hands-on back and forth scanning the bands. This VRT works
well in my findings. Some of you may not like this feature---at
all. In that case you can leave it disengaged. Also, it
should be noted that there is no electronic tuning knob lock
feature. Perhaps in a future firmware upgrade, one can be
implemented, as mentioned by the Reuter associate when I suggested it
to him.
SCANNING
FACILITIES: None! No scanner built-in as it was
designed. I wish it had it but oh well. You might think
otherwise, so be aware.
RECORDING FACILITIES: None! Ditto the above!!!
MANUAL: Available
only as a pdf on line at the Reuter-Elektronik website. I printed
one out in full color and placed it in a spiral bound binder, which I
vastly prefer over having to stare at a pdf on a computer or
smartphone. BTW, the manual is not stellar. It is
confusing. While generally well-translated from German into
English, it is overly long, it is not in build-version order and needs
some editing to remove German screenshot captions and to remove older
versions with different screen appearances, and obsolete features.
In conclusion, the
Reuter-Elektronik is a turbo-charged hot-rod among modern SDR-based
receivers, in terms of sheer performance and build-quality. It is
now my go-to receiver for down-and-dirty and long-term listening
sessions. It is one of those rare type radios that excels at
DXing and easy listening, and does so without sacrificing one aspect
over the other. The downside is cost. It is very expensive
and rather difficult to obtain outside the EU. Of these two,
obtaining one is much less an issue than having the money to buy
one! Fortunately, there is a work-around in purchasing one
outside the EU. Inquire at the website about how to get
one. It is a winner in many regards. I am very
pleased with it and I feel confident that you be, too.
Dean Bianco
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