Retevis  RT73
The RT73 is to date one of the smallest dual band DMR mobile I've seen (approx 5x3x2"), about the size of a handheld.  If you have limited space to mount a radio, this DMR/Analog might be a possibility.
 
 
In the Box
Included with the radio are the:
-  Microphone
-  Mounting Bracket and Screws
-  12V power Cord - 6.5' (2.0m)
-  60 page User Guide - (10x6) 6 languages
-  GPS Antenna
-  Programming Cable
 
 
General Description
-   DMR / Analog 
-   Dual Timeslot (MotoTRBO compatible)
-   VHF / UHF Dual Band
-   Size:  4.75 x 3.0 x 1.7"  (121 x 76 x 43mm)
-   Weight:   11.6oz   (329g)
-   136-174   400-480 MHz 
 
-   5w-20w transmit
-   300,000 DMR DB IDs (w/ Latest FW/SW)
-   20,000 call groups
-   4000 channel
-   Analog APRS
-   16 zones (250 Chan / zone)
-   Built in GPS
-   DMR Roaming
 
 
Enclosure

The RT73 case is less than 5" across and weighs in at 11.6oz  (329g). There's a rear mounted heatsink and fan assembly for cooling, making it ideal for dash mounting or tight center consoles.

The fan is thermostatically controlled and remains off until there is heat build up. When on, fan is very quiet.
 
The rear of the case has two antenna connections. An SMA-F is used for the GPS, while the SO-239 handles the main antenna. The programming jack is located on the left side of the case.
   
Along with Power On/Off, there are 3 programmable keys, Volume/Squelch, and A/B select buttons. (shown on the enlarged image below). The function keys respond to both short and long presses.
 

click on images to enlarge

Transmitter
 
The frequency range is VHF 136-174 and UHF 400-480 MHz, supporting both DMR and Analog (NB/WB).
 
The power levels hold very close to the specifications. There are two power levels with a low around 5.0W and a high clocking in at around 20W.
 
Power levels are listed below and were taken using a calibrated Bird Termaline wattmeter.
 

 
Microphone / Speaker
 
Along with the speaker in the radio, the RT73 also incorporates a speaker in the microphone. You have the option to select the speaker in the radio, the microphone, or both.
 
There is a microphone gain option as well. The ideal settings on my radio are MIC1=8dB / MIC2=10dB. Anything much higher is over driven to the point of distortion. My audio reports on the local repeaters have been excellent.
 
The microphone also has up/down keys as well as 4 programmable keys each with Long / Short press options. The keypad has no backlight and the microphone buttons are a bit small for my large fingers.
 
The radios .5 watt audio amp is used to power both the speaker in the radio and Spkr/Micr.
 
Note: I noticed that the DTMF tones via the keypad do not function. The company is aware of this and is on the 'bug fix' list.
  Receiver / Audio / Squelch
 
The receiver sensitivity is very good on both digital and analog and the receive audio quality is good, however high pitched due to the small speaker.
 
I found the analog squelch settings were a bit loose. Full (level 9) still allows low level signals to easily open the audio. This is not an issue on DMR, but noticeable when using on analog.
 
I was told the engineers are aware of the squelch issue and it should be corrected in a future firmware update.
 
 
Receive CTCSS
 
Heat can be an issue when CTCSS tones are used on the receive side. Although not noticeable after short transmissions (30 seconds or less), the receiver recovery after longer transmissions could be upward of 30 seconds. You can see the active signal on the LCD, but no audio comes through the speaker.
 
If this occurs, remove the CTCSS tone assigned to the receive side of the channel. The transmit tone is not affected by this, so accessing repeaters is not an issue.
 
 
Promiscuous Mode (Digital Monitor)
 
The  RT73 has a Digital Monitor mode which is Time Slot dependant. It allows you to receive any transmission on a specific time slot. If your current channel is on TS1, this will allow any transmission on TS1 to be heard, regardless of its talk group.
 
This function can be assigned to a programmable key by selecting the "Promiscuous" option.
 
 
Display
 
The multicolor high resolution screen size is 1.2" x 1.5" (2" diagonal). Here's are a few examples of the display. The last two images shows the database display options.
  

click to enlarge

 
Software

The software is a bit different than most. The standard programming sequence is:
(1)  Create a Contact (TG) list.
(2)  Create your channels in the Channel area
(3)  Move the desired channels into one or more Zones.
 
The RT73 is a bit different.
(1a)  Create a Contact (TG) list.
(1b)  Create a Duplicate entry in the RX Group List (There is no default option)
(2)  Create a Zone
(3)  Individually build each channel within that zone. 
     If the same channel is to appear in 2 separate zones, each must be built separately.
  
Software Observations:
- No re-sequencing of channels within zones
- New lines cannot be inserted (all channels added to bottom of list)
- No cut / paste
- No channel or zone import / export  (.csv)

Always take a Software backup before, during and after making changes.
 
Note: There are 3 Time Slot options. TS1, TS2 and ON. When operating on simplex or using a Hotspot, the Receive Time Slot needs to be set to ON.
 
 
Firmware
 
As additional features and future enhancements are developed, the radio can be updated to latest model. Updates can be done using a Windows computer in about 5 minutes.
 
 
Programming Cable 
 
My RT73 came with the necessary programming cable with the UART chip inside the USB connector. This is the same cable used by many analog handhelds with a standard K1 connector. The cable I received has a UART chip manufactured by Prolific. The latest correct driver should load automatically when the cable is inserted. If there are driver issues, Prolific driver 3.2.0.0 can be found HERE.
 
Conclusion
 
My radio works fine. There are a few minor issues mentioned above, but Retevis is responding to these with firmware and software updates, so they are definitely on the right track.
 
The Features include:
-  Small size
-  Nice heatsink and fan
-  300K DMR UserDB capable (latest SW/FW)
-  Bright color display
-  Programmable microphone gain
-  Promiscuous Mode (Digital Monitor)
-  Digital Roaming
-  GPS
 
Current Concerns:
-  No DTMF functions (Retevis is aware)
-  Full Squelch passes weak analog signals
-  Heat issue with Rx CTCSS (June 2022)
 
 
Notes:
 
I highly recommend using the latest Firmware and Software for the latest fixes and features.
The latest stable release of the RT73 software can be found at the Retevis website.
Select 'Support', Then 'Firmware/Software'.
 
 
Note: This equipment was received for the purpose of a fair and unbiased review. All findings are factual based on the equipment I received. Any issues found have been reported both here and back to the seller or manufacturer.