Tuesday, 16 August 2016

Review: Soft66RTL3 All-in-One

August 16th, 2016

$38 dollars shipped: RTL-SDR based receiver with upconverter and band preselector, thermal pad and heatsink. In a metal case. Covers DC to daylight.
Too good to be true, so I ordered one.
Available on maker's webpage (link). Turns up on ebay from time to time, not available at the moment.

First impressions

Delivery took 15 days from Japan to Ireland, unassuming brown postal envelope, receiver carefully covered in bubble wrap and a final plastic layer - unwrapping literally felt like Christmas came early.
Marginally larger than a regular RTL-SDR dongle, connectors protected by translucent yellow caps, tough-looking aluminum shell (not a full enclosure) sided by two rubber/plastic/unidentifiable material at connectors.

Side panel gap on one side was significant enough between cover and metal housing that light shone through.
No antenna, power cable, instruction manual, thank you card, but that seems to be the norm with small-scale manufacturers.

Importance of cable

Needs a USB Mini-A cable for data/power: noise pickup was terrible with a plain and long cable. One more cable and connector type to hunt down - could please manufacturers settle on Micro-USB and offer the option to order one along with the receiver? Thanks.
If buying new, shop for the shortest cable with one or two blobs on each end. Those metal cylinders are called ferrites, and will lower radiated noise pickup from household items.

Snap-on ferrites are an alternative and only cost a few dollars.


Antenna connectors: SMA Female, compatible with handheld transceiver antennas and premium dongles' antenna cable.

Two separate connectors, one for HF (below 30 MHz) and one for higher frequencies - two antennas can be connected at the same time, like a discone for 30 MHz and up, and a dedicated wire for below.
HF connector is right next to selector switch, easy to identify, red = HF.

Preselector and LED: 4 bands selectable with red rotary switch, which is also removable - slot for screwdriver on both, attention to detail.
Small hole: says "RF gain" on the product webpage, does nothing above 30 MHz. Needs small cross-headed screwdriver.

Take it apart

Remove two massive screws (largest and toughest ever seen on any dongle-related product) from the preselector side, board slides out from grooves integrated into the side shell.
Text on board by a tripping post-apocalyptic beauty pageant:

FUKSHIMA Human extinction

Architecture is pure genius: a tiny dongle (marked by red lines in the image) piggybacked onto a printed circuit board (PCB). Dongle's antenna connector is soldered onto the PCB's SMA connector, presumably by hand, fingerprint visible on back of board. Talk about personal touch.
Thermal pad and heatsink stuck onto dongle, blue material is much more stickier than $1 China pads or the SMArt's layers; remained sticky after countless removals.

Top of heatsink and chips on other side leave a minimal gap.

Band preselect and upconverter

Uses 50 MHz local oscillator.

Product webpage shows wrong settings.
Red knob with clicks, numbers on the dial, turn to a number and signals in the corresponding range should be better (called a band-pass filter in radio speak).
LED lights turn red for 30 MHZ and up, and green for HF:
Position 4: 0.4  to 1.2 MHz (LED green)
Position 5: 1.2 to 5 MHz (LED green)
Position 6: 5  to 15 MHz (LED green)
Position 6: 15 to 30 MHz (LED green)
Other positions: upconverter off (LED red).
Turning the knob in VHF and UHF has a small effect, 8 and 9 are the same, zero raises the noise floor.

On HF, wrong setting will completely eleminate received stations.


Worked with SDRUno straight away (beginner start guide here link), latest SDRSharp did not recognise receiver, but previous version functioned well.

Drift, heat, tuner

Weird behavior, three stages:
1. Extremely rapid drift, then a jump,
2. Gradual drift to 26 ppm in 5-6 minutes, then
3. Slow final settle in an additional 8-10 minutes.
31 ppm final once thermal equilibrium reached.
Case temperature by hand is well below other metal enclosure dongles.
R820T designation refers to the tuner part of any RTL-SDR dongle: determines receive performance. Newer and more sensitive version is called R820T2, used in recent dongles from $8 generics to $20+ premium products.

Performance VHF and UHF

Same outdoor pro discone antenna I use for years, and staple testing signals were simply not there. Constant and weak data dowlink in the image below, 420-ish frequency, exact value removed as I suspect it's government comms:

Sensitivity is terrible all across the spectrum, and not just on weak signals: even local airport information system required the most gain to get the lowest Signal-to-Noise ratio, and sounded much less clear and noisy.
From top left: rtl-sdr.com dongle with R820T2, $8 chinese generic, old Terratec with R820T and Soft66RTL3 in bottom right corner, very strong local signal, numbers in dB are Signal-to-Noise ratio, higher is better:

ADS-B performance with an outdoor half-wave antenna on a ground plane metal box from a first-floor windowsill was well below average: 5 messages per airplane, when 30-35 is normal for my location.
After a week of daily use, and with a choice of either the Soft66RTL3 or any other dongle, I don't reach for the tiny black box.
Audio quality is not great, similar to listening to music with a thrift-shop earphone.
Constant buzzing, noise everywhere, like the neighbor shaving on a washing machine whilst simultaneously fighting a hive of bees.

HF performance

50 MHz is added to received signal, so 7 MHz will be heard on 57 MHz.
City center with 20 foot / 6.5 meters of wire, screenshot of 40 meters, signals everywhere:

At least it works reasonably well on HF with a nearly quarter-wave antenna for this particular band.
Have a dongle and thinking of plugging the Soft66RTL3 in with a USB cable? A Ham-It-Up from Nooelec costs $42 plus shipping, doesn't come with a metal case, but soothes with brand-name peace of mind and 6 months' warranty.
And better performance, R820T also used to give the Soft66RTL3 a chance, gain adjusted in software for best audio on strong shortwave broadcast station with a discone.

Ham-It-Up v1.3 with either dongles resulted in understandable audio, Soft66RTL3 was unintelligible.
Strongly suspect that the PCB board / upconverter part is quite noisy, compounded by less than stellar R820T dongle performance.


Disappointing, because this little all-in-one promises tremendous value for money.
Doesn't deliver: performance above 30 MHz is absolutely and comparatively sub-standard, HF works with a long wire.
38 dollars for the Soft66RTL3 is a waste of money; buy a generic chinese for $8 and try direct sampling if funds are short.
Better buys exist: spend 25 bucks and get a full, usable and high-sensitivity premium dongle package from either rtl-sdr.com or Nooelec.
Maybe if small size appeals, and you are desperate for a dongle plus upconverter.

PS. Soft66RTL3 for sale, one lady owner, always garaged, low mileage.


  1. Hello, could you make a review of FlightAware Pro Stick USB ADS-B Receiver.
    Thank you

    Greetings from Málaga

  2. I had the same bad experience with Soft66RTL3 I received in early August. I complained to the manufacturer about the poor reception, sent me another plate and was exactly the same. As receiver is a shame.