This review is for the GooZeeZoo TEF6686 Full-Band Radio Receiver (FBRR) purchased in August 2023 with firmware 1.18 patch 102.Like many other receivers near this price point, this unit is based upon a receiver-on-a-chip. Unlike many of the software-defined radios (e.g. the Malahite and ATS-series units) the GooZeeZoo FBRR is based upon TEF6686 silicon rather than Si4732. I mention this because the choice of silicon affects so many aspects of the receiver's performance and operation. The TEF6686 is designed specifically as a LW/MW/SW/FM receiver while the Si4732 is intended to receive digital TV signals and has been cleverly adapted for use as a radio. If you're used to Si4732-based radios, I think that you'll be *pleasantly* surprised by the responsiveness of the controls and display and the quality of the receiver (on both the RF and audio sides).The FBRR is housed in a plain-looking metal case. The case has a textured surface which is good for hiding smudges and fingerprints. One end plate holds the USB-C charging jack and indicator LED and a 3.5mm stereo headphone jack. The other end plate holds a combination power switch and volume control and a digital encoder. The front of the unit has cutouts for a small speaker, a large, bright, well-organized display and three pushbuttons. The top of the case has an SMA-F jack for the supplied telescoping whip antenna; other antennas may be attached via a SMA-M connector. The unit is unmarked save for two stickers. I suspect that the stickers will suffer from dings and scratches during normal use. If you don't like the stickers, they can be scraped off using a fingernail and the excess adhesive removed using a bit of adhesive tape.Power is provided by an internal LiPo battery. The vendor claims that the battery has a 5,000 mAH capacity. Battery life is in excess of twelve hours with the display running continuously at 50% brightness.The operation of the FBRR is smooth and responsive. All actions happen immediately; there are no pauses or missed inputs. The display can be turned off to further extend battery life.The audio quality, particularly with quality headphones, is excellent. The built-in speaker is pretty good, considering its size, but it's better suited for talk than music. There are no clicks or pops when changing modes or stations.RDS is always on for the FM broadcast band. Station data comes up quickly, even with stations that have only a moderately-strong signal. Importantly, the RDS information is blanked or changed *immediately* upon switching channels. (I've seen Si4732-based units in which the RDS data is displayed for a long time after switching to a station without an RDS signal.) Note that stale RDS data may still flicker intermittently in the display under certain signal conditions.The display shows indicators for all of the important state of the FBRR. Bluetooth and WiFi icons are no doubt present for receivers which add those hardware functions; those icons are always dim on this receiver.For manual tuning, there's an indicator to show whether you've tuned to the carrier frequency; arrows indicate that you should tune up or down, while a centered dot lights up alone to indicate that you've tuned properly.Received signal quality is indicated using several readouts: an S-meter, a modulation meter, a received signal strength indicator and a SNR indicator. The signal strength indicator reads in dBµV. The S-meter seems to be poorly calibrated; a Wikipedia article claims that a received signal strenth of 34 dBµV should correspond to an S9 reading. At 30 dBµV, the FBRR reports S5 rather than the expected S8 or S9. I don't consider this to be a defect; the same Wikipedia article points out that few receivers have accurate S-meters.Battery voltage is also shown on the display. I don't know whether there's a low-voltage warning or cutoff. I've been following advice to not let the battery voltage go below ~3.5V. The charge circuit turns off automatically; the charge LED turns off when charging has completed.A full charge (starting at just below 3.5V) takes about six and a half hours. Think of that as overnight. Of course, charging a less depleted battery will take less time.The display has indicators labeled "iMS" and "EQ"; these seem reserved for FM operation. The TEF6686 data sheet suggests that these should both be turned on.My FBRR arrived with a one-sheet set of English instructions that seem fairly complete despite not mentioning some of the indicators. Note that many of the controls have different functions depending upon receiver mode (auto, manual, memory) and band (LW, MW, FM, SW). Don't be afraid to experiment.I listen mainly to FM stations. This receiver is able to pick up low-power FM stations that I haven't heard on other receivers; I guess that means that the sensitivity is OK. I have a sight-line to a bunch of high-powered broadcast transmitters a few miles away; these produce a strong signal at my location but do not bleed into adjacent FM channels.The shortwave bands suffer at certain frequencies from spurious signals and from overloading due to strong local transmitters. In the portions of the SW bands unaffected by spurs and overloads, I have had good results listening to international broadcasts when propagation conditions allow.On interesting thing to note about spurs and overloads: these are signals, either internal to the receiver circuitry or externally by a powerful transmitter, that bypass the RF section of the receiver. When the receiver is responding to a spurious or overload signal, the modulation meter will show a *lot* of activity while the RF indicators will show uncharacteristically low readings.I can hear WWV clearly on both 10MHz and 15MHz at most times of the day.I have used the LW and MW bands very little, and will not comment regarding their function.Note that this is not a "communications receiver". It does *not* demodulate SSB, CW, Morse, RTTY, NBFM, SSTV, etc.The whip antenna shipped with the receiver (as pictured) fails to screw all the way onto the receiver's jack due to the width of the antenna's connector. I replaced this with a whip having a standard SMA-M connector. A rubber ducky works well for the FM band; I prefer the rubber ducky except when listening on SW bands.Some USB chargers are poorly-filtered and will inject noise into the receiver. Try a different charger. I've had good luck with adding a clip-on ferrite to the charger cable to attenuate some of the noise. Remember that the FBRR will go pretty much all day on a full charge of its internal battery.Radio experimenters will be happy to know that the FBRR has some settings to support the use of an external RF downconverter or active antenna. I have an idea of how these might be used, but have not exercised them.You may have noticed that this radio is available from a number of sources in a number of slightly different configurations. That's because the design -- both hardware and software -- is widely published. If you pay attention to the radio's splash screen as it appears briefly during startup, you'll notice a reference to PE5PVB.nl; this is the original design. Visiting this web site reveals a couple of TEF6686 designs summarized as blog posts. The posts link to GitHub repositories containing hardware designs, firmware, data sheets, instructions, etc. There are a number of forks of the PE5PVB repo; one nominally contains the version shipped by this vendor.As one might expect, the FBRR has a "hidden" bootloader in order to be able to flash new firmware. The FBRR has been thoughtfully designed such that the bootloader is accessed through the headphone jack. With the FBRR turned off, insert a thin probe and gently feel for the boot button about 2 cm inside; when you find the switch you'll feel and hear a distinct click each time you press the button. With the boot button pressed, turn the FBRR's power on; you may see the backlight flash at the edge of the display, but the display will remain dark. The FBRR is now in bootloader mode and will remain so until you turn off the power. If you now connect the FBRR to your computer using a USB data cable, the FBRR will show up as a "CH340" USB device (assuming, of course, that your computer's OS includes the driver).It's beyond the scope of this review to describe how to install new firmware or where to find said firmware. I have not personally attempted to install new firmware and am unable to remark regarding availability or compatibility.I have noticed only one definite bug in the FBRR's v1.18 firmware: when selecting a station in MEM mode, some text related to your selection is written onto one of the RDS fields. If the selected station has RDS, that text will appear on top of the text written by the MEM selection. My best guess is that the MEM text is debug code that was inadvertently left in the production build.One other apparent bug is that the rotary encoder tends to take one step in the wrong direction at first use after power on or mode change. This self-corrects as soon as you attempt to use the encoder for the first time, and does not (so far as I've noticed) recur until the display restarts.All said, I highly recommend the GooZeeZoo Full-Band Radio Receiver. This is a fine receiver for listening to voice and music broadcasts on local and international broadcast bands.Here's a cheat sheet for all of the controls:Power/volume: clockwise is on/louder; counterclockwise is softer/off.Red button (short press): cycle through UI modes: AUTO, BAND, MAN, MEM.Red button (long press): show setup menu; press again to exit setup.Yellow button (short press, MAN or BAND mode): cycle through bandwidth settings.Yellow button (short press, MEM mode): press twice to store current preset; encoder may be turned to select preset before second press.Yellow button (long press, FM operation): cycle between mono and auto-stereo headphone output.Blue button (short press, MAN mode): cycle through receiver modes: LW, MW, FM, SW.Blue button (short press, MEM mode): recall preset; encoder may be turned to select preset.Blue button (long press): turn off display/UI; press again to turn on display/UI.Encoder (short press, MAN mode): select frequency digit to be changed by turning the encoder.Encoder (long press, FM operation): cycle through four combinations of iMS and EQ enableEncoder (turn, BAND mode): select SW bandEncoder (turn, MEM mode): select presetEncoder (turn, MAN mode): select frequencyEncoder (turn, AUTO mode): scan to next active frequencyThere are also some hidden configuration functions. These are available when turning on the radio. The configurations I've discovered are:Hold red button and turn on power: (toggle) invert displayHold yellow button and turn on power: (toggle) reverse tuning encoderHold blue button and turn on power: analog meter calibration (unused)Hold encoder button and turn on power: (toggle) encoder type