TM-7 hardware mods

Inrico TM-7 network radio transceiver.
TM-7 Mobile GSM/3G/WIFI Network Radio Transceiver

Inrico TM-7 specifications

Model: TM-7
​CPU Frequency: 1.2 GHz
Platform: Microtek MTK 6572A
Operating System:  Android 6.0 'Marshmallow' 
RAM: 512M+4GB (Optional: 1GB+8GB)
Extended Memory: Up to 32Gb :  Internally fitted SDcard (use high speed SDcard for best performance)
Screen TP display: IPS2.45”  240*320 :  Works with 'Capacitive' touch screen stylus.
Input Power: 12-24V: Operates perfectly from regulated DC PSU or external battery from 7.2V to 24V
Internal Speaker: 45mm diameter speaker, 4W
Headset port: 3.5mm jack. Note: Plugging a headset or headphones into the headset port does Not mute internal speaker.
USB: MICRO USB 5-PIN socket (for data cable/OTG cable)
Microphone: External Plug-In 'fist mic'. Condenser mic element with PTT switch & coiled 8 core shielded cable.
Mic Socket Type: 8 pin 'RJ45'
Mic Socket Wiring: Pin#1 GND : Pin#2 Mic AF input : Pin#7 PTT (1k resistor to GND) : Pin#8 +5V DC output. 
Dimensions: 188mm x 58mm x 26mm

RF Network Bands: 
 WCDMA/HSPA/HSPA+ Band 1 2100 MHz : GSM/HSPA/HSPA+ Band 8 900 MHz : GSM 1800 MHz support
 (HSPA and HSPA+ enhanced 3GPP 16-QAM modes)   
Max RF Output Power: 
 GSM/HSPA/HSPA+ 900 MHz -32.2dBm : GSM 1800 MHz -30.3dBm : WCDMA/HSPA/HSPA+ 2100 MHz -23.5dBm 
 WIFI: 2.4GHz ISM band IEEE 802.11b/g/n (up to 150 Mbps)

US Version Specifications for 2G / 3G : (Data source: FCC certification/compliance test report)


RF Support Networks: GPRS (Class 12)
RF Bands: GPRS850 / GPRS1900

Uplink Frequencies:
 GPRS850 824-849MHz
 GPRS1900 1850-1920MHz

Downlink Frequencies:
 GPRS850 869-894MHz
 GPRS1900 1930-1990MHz

Max RF Output Power: 
 GPRS850 32.20dBm
 GPRS1900 30.30dBm

Emission Types:
 GPRS850 253KGXW
 GPRS1900 250KGXW

Modulation Type: GMSK

Internal Antenna Gain:
 GPRS850 0.2dBi
 GPRS1900 0.7dBi

​​ 3G 
RF Support Networks: WCDMA, HSDPA, HSUPA
RF Bands:  WCDMA Band 2  WCDMA Band 5

Uplink Frequencies:
 WCDMA Band 5 824-849MHz
 WCDMA Band 2 1850-1910MHz

Downlink Frequencies:
 WCDMA Band 5 869-894MHz 
WCDMA Band 2 1930-1990MHz

Max RF Output Power: 
 WCDMA Band 5 23.20dBm
 WCDMA Band 2 23.53dBm

Emission Types:
 WCDMA Band 5 4M17F9W 
 WCDMA Band 2 4M19F9W

Modulation Type: BPSK

Internal Antenna Gain:
 WCDMA Band 5: 0.2dBi 
WCDMA Band 2 0.7dBi

Version: V4.0 (EDR mode)
Data Rates: 1Mbps, 2Mbps, 3Mbps
Modulation Types: GFSK, Pi/4, QDPSK, 8DPSK
Channels: 79
Channel Separation: 1MHz
Frequency Coverage: 2402 - 2480 MHz
Max RF Power Output: 1.63 dBm (Conducted)
Internal Bluetooth Antenna: 1.3dBi

WiFi Standard: 802.11b/g/n (HT20)
Frequency Coverage: 2412 - 2462 MHz 
WiFi Standard: 802.11n (HT40)
Frequency Coverage: 2422 - 2452 MHz
Data Rates: 
802.11b : 1 - 11 Mbps
802.11g: 6 - 54 Mbps
802.11n: 150 Mbps
Modulation Types: CCK, OFDM, QPSK, BPSK, 16QAM, 64QAM
Max RF Output Power: 14.20dBm (conducted)
Internal WiFi Antenna: 1.3dBi

TM-7 Hardware Modifications


Any modification You make to Your equipment is done entirely At Your Own Risk.

The U.FL micro coaxial connectors are very small and somewhat fiddly to handle.

These precision connectors can be damaged if not correctly aligned during fitting.

If You are not entirely happy with performing any procedure or modification accurately and correctly I recommend getting someone else to do it who has experience with similar procedures involving very small high precision components or seeking assistance from someone who has worked with surface mount electronics.  

* You are entirely responsible for safe use and legal operation of Your own equipment. *

Sim card installation


SIM card installation in Inrico TM-7 Network Radio.

​Carefully place the sim with metal contacts facing the radio and gently slide SIM card(s) into the holder(s) making sure the SIM is correctly oriented (as shown above SIM1 / SIM2 slot identification text on the case) Gently slide SIM card into the holder (away from the slot identification text) until it stops fully 'home' against the top edge of the holder to ensure correct connection.
Replace the cover and secure cover in place with the two small screws before operation.

NOTE: If You intend to operate the TM-7 using WiFi connections only and do not want to use it on mobile networks You do not need to install a SIM card. The TM-7 will operate happily connected to Your home wireless access point or home WiFi router. For occasional portable operation You can tether it to a WiFi hotspot on another network radio, mobile phone or other portable WiFi hotspot device. 

SD MEMORY card installation

TM-7 SD card installation step 01

NOTE: The TM-7 will give You two options to format the new SDcard as  #1 'removable storage' or as #2 'internal storage'.
Option #1 

Will format the card as a 'removable storage' device (like a USB stick) this is OK as secondary storage but not for APPs.
Option #2

Will format the card and 'hook it into the operating system' as fixed internal storage that You can install apps directly into greatly expanding the size and number of APPs You can use on the network radio. : You can make large APPs and apps that require a lot of space (maps etc) use the SDcard and leave system APPs using the internal on-board storage.

(Some APPs can not be located on an SDcard and must be located in the devices internal memory, this depends on how each specific APP has been set up by the APP developer) 
When selecting an SDcard:

Make sure You get a high speed SDcard (Class 10 or better) to ensure the system runs smoothly.

Classic Desk Mic on TM-7

Leeson-Desk-mic on TM-7.jpg

I have been using an old classic Lesson desk mic on the Inrico TM-7

This is connected with TM-7 RJ45 8 pin mic plug to 4 pin inline mic socket adapter cable to suit standard 'Uniden' microphone wiring.

The Lesson TW232 desk mic is a solid old favourite.

The cast metal base, column and mic housing are quite weighty.
The large black bar is the PTT switch,

The lever on the right is the 'Mic Lock' (mechanical PTT toggle) 

The rotary knob on the left is the microphone gain control.

The mic gain circuit is powered by a 9V battery

(MN1604 type) fitted in the base unit.

TM-7 Mic Cable Wiring

Inrico TM-7 mic cable wiring diagram

Battery Powered TM-7

The TM-7 is designed to be used as a mobile network radio device in a vehicle powered by the vehicles 12V or 24V DC power system or used in a fixed location as a home/office 'base station' network radio powered by en external 12V DC power supply.


It does not have an internal battery but it does have an internal voltage regulator circuit that will accept a range of voltages from an external DC power supply or external battery with the internal regulator providing the required voltages to the internal circuitry for stable operation of the radio.

Although the specifications state the power requirement is 12 to 24 volts DC, The TM-7 will operate correctly using power from an external battery or regulated DC power supply from 7.4 to 24 volts. 

In the shack the TM-7 is powered from the shack 12V battery bank (charged from amorphous silicon solar panels)
In the house I use a 12V DC power supply. (when the mains power drops out I use batteries instead) 

I have used the TM-7 for mobile operation with power supplied by various different batteries including;

  7.4V Baofeng UV5R 1,800mAh battery pack.

   Operated well on 2.4GHz WiFi but suffered from occasional 'drop outs' on 3G due to frequency instability.

​  8.4V NiCd 6,500mAh battery pack (from an old radio controlled car)

   Operated perfectly on 2.4GHz WiFi and 3G with no 'drop outs'

  9V MN1604 type battery (for a short duration)

   Operated perfectly on 2.4Ghz Wifi and 3G for short duration. 3G became unstable after 1 hour.

  12V 'UPS' battery backup unit fitted with 4 x NiMh 2,100mAh AA cells.

   Operated perfectly on 2.4Ghz Wifi for 1.5 hours and 3G for 2.5 hours.

 12V SLA (sealed lead acid) battery pack.

   Various different SLA batteries with various capacities from 3.5Ah to 10Ah for long durations.


 18V 'power block' with 16 x 2100mA AA cells

   Operated perfectly on 2.4Ghz Wifi for 3.5 hours and 3G for 5 hours.

 I have also 'bench tested' the TM-7 using power provided by a 24V DC 'truck' battery supply and lab power supplies.

TM-7 Battery powered off road mountain bike mobile operation.

Inrico TM-7 network radio portable field pack.
Inrico TM-7 on mountain bike handlebars.
Inrico TM-7 camping
TM-7 network radio mountain bike mobile in Ayrshire.

 I have been using my Inrico TM-7 network radio out and about hill walking, camping and fitted on the handlebars on my customised VooDoo Wazoo FatBike for 'mountain bike mobile' operation off road around Ayrshire & the Galloway hills.

I have been using this setup to map out the coverage area of the few cell-phone towers around my local area and have been operating at extended distances from the cell tower sites using various external high gain antennas.

During antenna range testing on the mountain bike power is supplied to the radio from a 12V SLA battery mounted on rear carrying rack which easily provides over 30 hours of continuous operation.

​My network radios are also used for precise location tracking and mapping during off-road rides with GPS tracker APP running in the background recording elevation, speed, distance, heading, track, waypoints etc.


I also use network signal monitoring APPs in the background to record and map cellular network coverage of cell-tower sites while Zello runs in the foreground providing Global 2-Way PTT communications.

Operating time could be extended by using Zello on its own without GPS, mapping, tracking and cell signal monitoring APPs running in the background.

note: I use the TM-7 directly mounted on the handlebars when weather is dry and continued to operate with no problems with the radio enclosed in a heavy gauge plastic bag when caught in a thunder storm up in the hills several miles from home! ​ When going mobile in the hills It always pays to have a backup plan, just in case conditions deteriorate.


External Antenna Connection

A simple (but fiddly) modification to use external GSM/2G/3G antenna socket on TM-7 network radios.

Inrico TM-7 external antenna connection
Inrico TM-7 external antenna connection
Inrico TM-7 external antenna connction P3
Inrico TM-7 extenal antenna connection
Inrico TM-7 external antenna connection

Fitting an external antenna is especially useful when operating the radio in a vehicle or location where network signal levels are poor. 
There are two micro-coaxial connectors on the RF module, as shown above. The TM-7 is manufactured with the Male PCB socket connected to the internal antenna and an external 'pigtail' coaxial cable from the external ANT socket on the rear of the radio. (external antenna 'pigtail' cable is not connected but is provided as an option to enable use of external antenna for in vehicle installation. The pigtail cable is usually secured inside the rear case section with tape at the factory to ensure it does not make contact with any circuitry or components if not used)

The basic modification disconnects the internal antenna and connects the Female micro-coaxial connector on the 'pigtail' for the external antenna socket (factory fitted but not connected) to the Male PCB connector on the RF module. 
In this configuration You Must have an external antenna plugged in before powering on and attempting to operate the radio. 

If You wish to move the TM-7 between operating locations, EG;  Operating the radio in a vehicle installation with external antenna and also be able to unplug the radio power & antenna connections, remove it from the vehicle and operate elsewhere without an external antenna You will need to purchase a replacement pigtail cable with a Male U.FL micro-coaxial plug and connect it to the 2nd socket on the RF module (Female PCB mounted socket)

Important Notes

 With the external socket connected and the internal antenna disconnected. 
Do NOT attempt to operate the TM-7 on GSM/2G/3G cell-phone data connection without an external GSM/2G/3G cell-phone antenna plugged in as this may damage the output section of the RF module. You can safely operate the radio via 2.4GHz WiFi connections with no GSM/2G/3G antenna attached as long as You have either No Sim inserted or if You have SIM(s) inserted You have the SIM(s) switched Off. 

 With both the external socket connected and internal antenna still connected (as shown below) 
You can operate with or without external GSM/2G/3G antenna plugged in depending on location and network signal coverage

Inrico TM-7 RF module iPex micro coaxial connectors

- External Speaker/Headphone Socket -

Adding a hardware external speaker / headphone socket to the rear of the TM7 is an easy modification that will enable You to use any normal headphone with a standard 3.5mm stereo jack plug to listen to received audio. 

By fitting a 3.5mm stereo jack socket that incorporates mechanical switching, the internal speaker will be muted when headphones or speaker jack is plugged in to the socket. This is achieved by wiring the 3.5mm switching socket into the internal speaker wires that feed audio from the PCB to the internal speaker. When there is no external speaker or headphone plugged in the audio is routed to the internal speaker.