uv998 face Having recently acquired this small VHF/UHF UV-998 dual-band mobile transceiver from LEIXEN, here are some informations.
Measurements
Usage
Programming
Links

This radio is sometimes also named VV-998 !
Please share your own experience with me, so I can improve this page. 

Measurements :
Measurements made with my IFR 2945A service monitor.
Power supply 12.7 V under load on the radio power connector.

Common :
RX power consumption : All backlights ON : 117 mA, All backlights OFF : 99 mA

VHF 144-146 MHz
TX power : 5.6 W / 8.6 W / 21.2 W
TX consumption: 1.25 A  / 1.85 A  / 3 A
TX frequency precision : + 330 Hz
TX modulation max : 4.5 kHz (position WIDE)
TX modulation TCS (88.5 Hz) : 690 Hz
RX sensitivity : 20 dB @ 0.18 µV SINAD (@ 2.4 kHz deviation)
RX Squelch threshold .: 0.13 µV
RX distorsion : 3 %

UHF 430-440 MHz
TX power : 4.3 W / 9.7 W / 20.1 W
TX consumption :  1.34 A  / 1.86 A / 3 A
TX frequency precision : + 990 Hz
TX modulation max : 4.5 kHz (position WIDE)
TX modulation TCS (88.5 Hz) : 690 Hz
RX sensitivity : 20 dB @ 0.16 µV SINAD ( @ 2.4 kHz deviation)
RX Squelch threshold .: 0.12 µV
RX distorsion : 2.5 %

The frequency precision, although important to my taste, remains however in the announced characteristics. (+/- 2.5 ppm, that is 1075 Hz at 430 MHz)
After opening the radio, I saw that there is no way to correct the frequencies. The TCXO has no tuning possibility. It should however be possible via a calibrating software, as the TCXO control pin is connected to a microcontroller DAC output.

The powers measured at 12.7 V under load would certainly be higher at 13.8 V.
The other values are also nominal.

Usage

In use, this little set gives me full satisfaction !
It is flexible in use, the programming software allows all the useful possibilities for radio amateurs. Many functions are however dedicated to a more professional management.

The case is partly made of die-cast aluminium and seems to be sturdy. The display is large and readable, compared to many other "low cost" sets.
The microphone has a good grip and has a small built-in speaker which gives good results. It has all the necessary functions, including 2 programmable PTT keys !

In transmission, the modulation reports were all good. The output power is more than sufficient. The set heats up quite a bit in HIGH position if you stay too long in transmission, which considering the size of the set and the lack of fan, is not surprising.

On receive, the sensitivity is excellent as well as the quality of the sound. The small loudspeaker integrated in the set is excellent considering its size!
On high level radio sites, the receiver suffers from desensitization, but less than many ICOM, YAESU, etc... Which is surprising.

A small drawback is the size of the ON/OFF and V/M keys which, located above the microphone connector, are very small and difficult to access.

All in all, this little set has an excellent quality/price ratio!

 Programming

The VV-998 is programmable via the software available on the LEIXEN website. The VV-998 is not (yet?) implemented on CHIRP.

There is no help available, neither in the software nor online. Leixen has not answered to my emails..
Some choices are not easy to understand or contain errors, here are some explanations.

  

 OPTIONAL FEATURES   Menu
APO  Auto Power Off : delay before the set is turned off after the last use. 01
Squelch level  Default squelch level setting. 37
Scan Key Scan mode : CO (resumption after 2s of inactivity on the channel), TO (resumption after 5s even if communication in progress)  
Time Out Timer  Maximum duration of the transmission. OFF or from 10 to 120 s 40
Step  Frequency step increment value, from 2.5 to 25 kHz 38
Monitor  CTC/DCS, DTMF and CTC/DCS,  DTMF or CTC/DCS  
Volume  Default volume level value : OFF to 15  
Open Display  Display at startup. ALL (all segments), LEASE TIME, USER-DEFINED, LEIXEN (displays LEIXEN)  
Custom display  Text to be displayed when starting in "User-defined" mode  
Backlight  Backlight. OFF, KEY (lights up momentarily when a key is pressed), CONT (continuous)  
Key lock mode  Pressing the MENU button on the radio for 1 second locks the radio.
What should be locked? K+S (keypad + arrow keys), PTT (PTT), KEY (keypad), ALL (all)
 
A/B select  Selection of the default memory bank at startup, A or B  
PTT set - Per minute  Number of PTT activations/minute. icons8 error 16 If this number is exceeded, it is impossible to switch back to transmission before the minute has elapsed.  

 

 CHANNEL A/B    Menu
 VFO/MR  Choice of channel mode at startup, MR = memory, VFO = VFO frequency  
 MR/CHA  Choice of display at startup, MR CHA = channel name only, Freq MR = channel number + frequency (or name if selected)  
    Menu
Open beep  Activates the 3-tone beep at start-up  
Roger beep  Activate the sending of a roger-beep at the end of each transmission 29
Key lock  Activate the key lock by pressing and holding the MENU key 17
CTC/DCS busy lock  Activates the prohibition of switching to transmission if the frequency is busy (works with the BLCK parameter on the channel) 03
Alarm key  ?  
Battery save  Battery saver ON/OFF 33
Key beep  Beep when an ON/OFF key is pressed 04
Reset Enable  Allows the possibility of doing a RESET of the station (after start-up, press 2s on the MENU key of the radio during start-up display)  
Small font   ERROR ! corresponds to FRONT ! Activates the microphone speaker (ON) or the internal speaker (OFF) 16
Alias enable  Activation of channel name display ON/OFF. Must also be activated by channel in the "Channel information A and B" tables 21
TX stop  No transmission. No transmission possible, a beep will be emitted when the PTT is pressed 42
DW  Double watch on the 2 bands ON/OFF  
FM enable  Enables 88-108 MHz broadcast receive ON/OFF 12
FM DW  Enables double watch of channel activity while listening to FM broadcast. ON/OFF 15
FM scan  Operating mode of the Up and Down keys in FM broadcasting. ON (scan start) OFF (manual setting in 50 kHz steps) 13
Keypad MIC  Allows the use of the microphone keypad  
Open  ?  
PTT A=B  ON = Both PTT buttons can be assigned to the band in use, OFF : PTT up = band A, PTT down = band B 28
 VOX    Menu
 VOX Gain Level  VOX gain 1 to 8. Can be disabled by menu 43 (OFF)  45
 VOX delay time  VOX delay : 1 to 4 s  44
 VOX inhibit on receive  Disables VOX in reception ON/OFF  46

 

SPECIAL functions

SYSTEM  Settings for sending the identification sequence by DTMF.   Only useful with VV-998 sets  Menu
 Digit time (ms)  Duration of each tone  
 Digit space time (ms)  Duration of the interval between each tone  
 First digit delay (ms)  Duration of the 1st tone  
 Pretime (ms)  Duration before sending the 1st tone  
 * and # delay (ms)  Duration of codes * and #  
 ACK decode  Decoding the acknowledgement of receipt  
 DTMF sidetone  Local DTMF monitor  
PTT ID  Allows the identification of the station during a transmission by sending DTMF codes or spoken. Validation by channel with PTT ID Menu
 Display PTT ID  Enables the option to display the identity of the sending station on the remote station  
 Voice ID  Validates the option of identification by a voice  
 PTT ID  Choice of sending the ID at the beginning or end of the transmission  
 Begin of TX  ID at beginning of TX  
 End of TX  ID at end of TX  
 PTT ID over time    
 Voice announcement  Choice of voice language English or Chinese.  
 Voice time [MS]  ?  
 DECODE    Menu
 Group ID    
 Primary ID    
 Auto reset time (ms)    
 DTMF beep    
 Auto ack    
 Strip CTC/DCS    
 Display 14 bit ID    
 Wireless change chnl  Allows remote reprogramming of channels in a VV-998 fleet
 Function enable  Validation of the reprogramming function
 Wireless start  ?
 Start ID  Code that triggers the reprogramming
 Master Enable  Validation as master station
 STUN  Function allowing to deactivate remotely the reception or the emission of the station. (theft, jammer..)  Menu
 Activation enable  ON/OFF  
 TX inhibit  ON/OFF icons8 error 16 MUST be checked even if the STUN function is not used, otherwise no transmission  
 TX inhibit activation  Code DTMF à envoyer pour désactiver l'émetteur   
 RX inhibit  ON/OFF icons8 error 16 MUST be checked even if the STUN function is not used, otherwise no reception  
 RX inhibit activation  DTMF code to send to deactivate the transmitter  
 LEASE  Function managing the duration of the lease of the station. Useful to manage a lease of stations.  Menu
 Activation  ON/OFF  
 Remainder prompt    
 Time-Out  Date and time of the end of the lease  
 Time of system  To set the date and time of the station to the computer time  
 Communication password  Change your password ?
 SQL base value  Setting the Squelch Scale Range
 RSSI 400  RSSI value squelch opening on 400 MHz
 RSSI 136  RSSI value squelch opening on 136 MHz
 Enable change  Check to save changes

 

Key Assigment

uv998 key assigment

 Key Assigment  V/M and MENU function key settings
 Long press  Delay in seconds for a long press
 P1 long  Selection of the function for a long press on the V/M key
 P1 short  Selection of the function for a short press on the V/M key
 M short  Choice not available
 MENU enable  Allows the use of the MENU button
 Autodial memory  Programming of 16 memories for sending "autodial" DTMF sequences accessible by the microphone using the CALL button  Menu
 Long press time  Duration in seconds for a long press  
 P1 long  Choice of function accessible by a long press on P1 (V/M key)  24
 P1 short  Selection of the function accessible by a short press on P1 (V/M key)  25
 M short  Modification not possible. (default, key lock)  17
 Menu enable  Check to activate the menu  

 

BAND SELECT

uv998 band select

 CHANNEL INFORMATION A et B

icons8 error 16 The UV-998 has 2 channel banks A & B. These banks can be completely different or the same.
In this later case, the banks can be copied with the help of the "To B channel" when programming bank, and vice-versa.

uv998 channels

 QT/DQT Dec  QT = Quiet Talk, DQT = Digital Quiet Talk equivalent to TCS (Tone Coded Squelch)
 Band Width  NARROW / WIDE sets the maximum excursion according to the channel spacing. 2.4 kHz or 4.5 kHz max
 Scan Add  ON / OFF The channel will be added to the list of scanned channels
 Tail Cut  ON / OFF Allows you to limit the squelch noise at the end of a transmission
 APRO  OFF/COMP/SCRAMBLER/RX SCRAMBLER/TX SCRAMBLER enables the modulation compressor, modulation encryption
 VOX  ON/OFF activates the VOX
 PTT ID  ON/OFF activates the sending of the station identification on a transmission passage. Parameters to be set in menu 27
 DTMF  ON/OFF enables the use of DTMF
 CH Alias  Channel name, maximum 6 characters
 Alias open  Allow the channel name to be displayed
 Reverse  Allows Reverse operation (TX/RX frequency swap). Parameters to be set with menus 30, 31, 32.
 Talk around  Enables the Talk Around function (communication on the output frequency of a relay). This parameter is to be used with menu 40.
 Custom QT/DQT  Entering a special TCS frequency
   
 To B channel  Copy from channel bank A to B (and vice versa)
 CH clr icons8 error 16Deletes ALL channels
 CH up  Raises the content of the channel by one notch
 CH dn  Lowers the content of the channel by one notch
 CH del  Deletes the channel

Liens :
Leixen download center
Aliexpress seller (recommended, proceeded to a shipment of a defective microphone)
Manual in PDF OCR format