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Locking down a Baofeng UV5R+ to disable unintentional TX

Apr 12 2015

The Problem

In Austria a licensed HAM radio operator has to ensure that nobody (except other licensed HAMs) can make transmissions from their equipment. This may be a simple task if you put away your radios from your family all the time, but the Baofeng UV5R+ has a bunch of interesting features like a torch lamp (OK its just a LED on the top, but in the most cases this my be sufficient) or a built in FM-radio that can be useful in your house.

baofeng_uv5r.png

So if you want to follow the regulations then you have to ensure that unintentional transmitting is not possible by all people who have access your device. In other words: you have to cripple your device up to a certain extent. In my special case I wanted to be able to use the device for APRS (in combination with mobilinkd) and I wanted to preserve the ability to transmit if a connect a headset.

The solution

There are multiple ways how to disable transmitting on your UV5R. Some of them require hardware modifications, other ones can be done within software.

Software modifications

All the describes software modifications can be done with the chirp software. Under Ubuntu 14.04 it can be installed with the command sudo apt-get install chirp

The software is able to backup the current settings, modify them and update them on the device. I did the following:

  1. Backup the old settings (maybe I will need them in the future)
  2. Set the correct memories like my home repeater, APRS and so on.
  3. To minimize current consumption: Disable Standby LED
  4. Disable Roger Beep (needed for APRS with mobilinkd)
  5. Set Squelch Level to 1
  6. Set Alarm Mode to SITE (Site means that the Alarm button does not transmit anything if an alarm is raised)
  7. Set Automatic Keylock to on - Now my family can not modify settings unintentionally
  8. Enable Broadcast FM radio
  9. Disable Squelch Tail Eliminate and STE Repeater Delay
  10. Disable All Menus (including Reset Menu). So nobody can change the settings on the radio.
  11. Disable TX on 70cm by setting Lower frequency higher than upper frequency
  12. Leave TX on 2m enabled, but set to 144-145 MHz (to enable APRS on 144.8MHz)

You can have a look at the modifications by importing the attached chirp file that locks down the UV5R to APRS.

Hardware modifications

This was a simple one: If you want to disable TX then you have to modify the TX button or the circuitry. The complete removal of the TX button would be an attempt, but this process is not reversible any more. So I went with another solution: Within the Uv5R there is a thin rubber pad that pushes against the TX button. This pad can be easily cut of with a sharp knife. After that the TX button on the UV5R does not work any more while the TX circuitry is still untouched.  This means that the TX with the headsed plugged in is still working.

uv5r_disable_tx.png

The Result

In the end i had a radio that is only able to transmit if you connect a headset or any other device to it. All other possibilities to transmit are disabled - even the ALRAM mode of the UV5R. Now I can leave it in my kitchen as FM radio without the worries that my family unintentionally transmits something by wrong operation.

73, OE6GUE

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