[ Don't have a UV-5R yet? Get one here. ]
Alvin and b1gslacker have been editing the .dat file to expand the receive frequencies of the UV-5R. As usual the results are a big of a mixed bag given the limitation of the hardware and software involved. Steve, WB8GRS, details the limiting factors:
"There are two components (the DSP and MCU chips) in the UV-5R that determine the band limits.
1. The RDA1846 DSP chip is the chip that generates all the transmit and receive functions and it specifies the band limit as follows.
134 MHz to 174 MHz200 MHz to 260 MHz400 MHz to 500 MHz
This information is provided in the RDA1846 documentation in the file area. Many have reported the UV-5R will operate outside of these band limit on the 134 to 174 and 400 to 500 MHz bands (no one has reported any success using the UV-5R on the 222 MHz band), so my guess is the above band limits are not "hard coded" in the DSP chip, but are just guaranteed band limits and in fact some chips may operate outside these band limits to some degree.
2. The MCU which I believe is a custom version of the EM78P568-44 microprocessor tells the DRA1846 DSP chip what frequency to tune. If the MCU does not send the correct commands to the DSP chip the right frequency will not be received or transmitted. If for example you load in a 222 MHz frequency, the DSP chip is capable of receiving and transmitting on 222 MHz, but only if the MCU provides the correct commands to the DSP chip. If the MCU does not provide the correct commands, the display may should the correct frequency, but the DSP chip is doing nothing. Even if the MCU send the correct commands to the DSP chip, the RF pre-amplifiers and RF amplifiers external to the DSP chip are not designed to operate on the 222 MHz band so even if the DSP chip was commands correctly by the MCU, the power output and receiver sensitivity would likely be very bad."b1gslacker gives the details of how to make the change here. The usual warnings apply - do this at your own risk.
"For those of you who would like to attempt to destroy your brand new shiny UV-5R, here are the instructions for "slightly modifying" CHIRP to accept frequencies WAY outside of the manufacturers recommended operating boundaries. These instructions are for windows XP only (but will probably work for others also)
1) Download the UV5R.pyc file in the files section.2) Using your favourite zip utility (I recommend winrar) open the library.zip file located in your C:\Program Files\CHRIP\ directory (location may slightly differ based on your flavour of windows, but you get the idea).3) Delete the UV5R.pyo file from the zip4) Add the UV5R.pyc file5) Save the modified library.zip
I know that your thinking, but if you don't understand the instructions, you should definitely not be trying this, so don't even ask.
Now that you have installed the "ever so slightly enhanced" version of the UV5R CHIRP module you should be able to program frequencies between 10MHz-999MHz in the CHIRP application.
NOTE: Even if the radio accepts the frequency and displays it on the LCD display, this does not mean that the radio will actually work on that frequency (in fact we do know that there are definitely limits)"