Rx wider frequency range
Posted: Sat Apr 18, 2020 1:46 am
Someone commented to me, a while ago, that the using the official firmware they were able to receive on a wider range of frequencies than allowed by the OpenGD77.
I did some tests with several of my GD-77s, and it looks like the Rx frequency range can be extended, beyond the published specification of the baseband RF chip (AT1846S)
My radio seems to be able to receive (and also to transmit into a dummy load) on these ranges of frequencies
128Mhz - 177Mhz (Datasheet values are 134Mhz - 174Mhz)
190Mhz - 280Mhz (Datasheet values are 200Mhz - 260Mhz)
380Mhz - 560Mhz (Datasheet values are 400Mhz - 520Mhz)
Some of my GD-77 will go slightly beyond those limits, but not all of them will, so I think that the PLL is not locking on all my radios if I go beyond this range.
I'd be interested to know if everyone's radios seems to operate over this range, or whether I need to reduced it a little to guarantee that its OK for 99% of users.
I've also made a change to the code, so that the UHF Rx and UHF PA is used for all bands except for the VHF, as this gives results when listening below 400Mhz, but above 177Mhz
I also did another failed experiment of setting the baseband clock input setting to 13Mhz, even though its being supplied with 26Mhz from the master reference oscillator, in the hope I could receive above 560Mhz by specifying half the frequency but using twice the clock frequency.
e.g. 380Mhz x 2 = 760Mhz. But the PLL didn't seem to lock at all if I did this.
So I think this is the maximum frequency range which can be achieved.
The range limits I've put in the firmware are
127MHz - 178MHz
190MHz - 282MHz
380MHz - 564MHz
I did some tests with several of my GD-77s, and it looks like the Rx frequency range can be extended, beyond the published specification of the baseband RF chip (AT1846S)
My radio seems to be able to receive (and also to transmit into a dummy load) on these ranges of frequencies
128Mhz - 177Mhz (Datasheet values are 134Mhz - 174Mhz)
190Mhz - 280Mhz (Datasheet values are 200Mhz - 260Mhz)
380Mhz - 560Mhz (Datasheet values are 400Mhz - 520Mhz)
Some of my GD-77 will go slightly beyond those limits, but not all of them will, so I think that the PLL is not locking on all my radios if I go beyond this range.
I'd be interested to know if everyone's radios seems to operate over this range, or whether I need to reduced it a little to guarantee that its OK for 99% of users.
I've also made a change to the code, so that the UHF Rx and UHF PA is used for all bands except for the VHF, as this gives results when listening below 400Mhz, but above 177Mhz
I also did another failed experiment of setting the baseband clock input setting to 13Mhz, even though its being supplied with 26Mhz from the master reference oscillator, in the hope I could receive above 560Mhz by specifying half the frequency but using twice the clock frequency.
e.g. 380Mhz x 2 = 760Mhz. But the PLL didn't seem to lock at all if I did this.
So I think this is the maximum frequency range which can be achieved.
The range limits I've put in the firmware are
127MHz - 178MHz
190MHz - 282MHz
380MHz - 564MHz