Richard Perlman wrote:
This feature request is to address an undocumented (in the UI) behavior. On the GMRS-V1 radio, the first 15 memory locations (0-14) operate simplex (offset = 0) and locations 15 to 22 operate with a +5mHz offset. Then, locations 23 to 127 are all simplex. This is a limitation of the radio, no doubt required to gain thorpe acceptance. However, because it is not visible to the CHIRP user it is easy to create problems. For example: I had a request to set GMRS-1 to location 1 so the numbers lined up. I did that by moving all the locations down by one, leaving location 0 open. However, when the user tried to transmit simplex on location 5, they were actually using an offset of +5mHz.
The RX and TX frequencies of the GMRS-V1 channels 0 through 22 are fixed in the firmware and cannot be edited or relocated. Channels 0 through 6 (the shared FRS channels) are also bandwidth fixed to NARRow. This was a FCC requirement in order to achieve Part 95A certification.
To get channel 0 to look like channel 1, you will have to use the channel Name to call it channel 1 and set the Memory Display Format (MDF-A or MDF-B) to NAME (which that is the way the GMRS-V1 comes from the factory).
The user could not transmit on channel 5 with a +5 MHz offset because it is impossible to change the TX frequency. The channel 5 simplex frequency of 462.6875 MHz is fixed at the factory. If you edit any of the "fixed" frequencies and upload them to the radio, when you download from the radio back to CHIRP the original factory frequencies will again be displayed.
The frequency assignments for channels 0 through 22 are documented on page 32 of the GMRS-V1 user manual.
The suggested fix would be to add a dummy column for Duplex and offset. The values would be fixed (grayed out in the UI). However, the presence of this information would make the behavior of the radio clear to the programmer.
The Duplex and Offset columns are used to edit TX frequencies. The TX frequency for memory rows 0 through 22 are fixed and cannot be changed, so there is no TX frequency to edit in these channels. Memory rows 23 through 127 are receive only, so there is no TX frequency to edit in these channels. So there is absolutely no need to have a Duplex or Offset column because there are no TX frequencies in this radio that can be edited. Only the columns that can be user edited are included in this driver.
Jim KC9HI