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appendix implementing in a ic 7300
While the IC-7300 is marketed/sold as a SDR, we are not short of 7300 panadapter projects - a quick Google search will reveal a number of projects.
If you are interested in implementing this project in a 7300, I found that it might work - with a few design changes.
Differently from the heterodyne technology, the IC-7300 does not provide a external Intermediate Frequency (IF) port - It uses the Direct Sampling technology, which has a FPGA that does the RF signal conversion to digital.
There's the beautifully crafted the PTRX-7300 board - at the hefty price tag of approx. $ 200 - a fifth of a new IC-7300 price.
The PAT-991 could be a el-cheapo alternative, almost a order of magnitude less expensive - though, untested. Matter of fact, the Light Edition board would be more suitable.
As aforementioned, the IC-7300 has no external Intermediate Frequency - So you have to tune the real frequency in the SDR, instead of the IF frequency conversion trickery.
Since there are no Bandpass filters activated by default in the PAT-991, the board would amplify the resulting band after the IC-7300 initial bandpass (there are 13 of them, ensuring only band-of-interest signal to the SDR) - Stick to the Light Edition](https://github.com/rfrht/FT991A-PAT/tree/PAT-Light) board.
If you are interested in lodging the SDR inside the IC-7300, this is also possible: This equipment features a 4-port USB hub from factory, so there's no need to replace / resolder the USB hub like in the FT-991/A: It is perfectly possible to lodge it inside the equipment and send it downstream to the existing USB hub without having to exchange main unit components.
The USB signal can be tapped from IC621, ports DP2 and DM2 (PCB, schematic) - Icom was kind enough to provide easy access to solder pads. Remember the obligatory 27 ohm resistors between the SDR and the USB DP and DM lines.
The +5V power line to feed the SDR would have to be tapped from the IC251 1.5A switching voltage regulator (PCB, schematic).
There are plenty of +13.8V tap points - this should be of no concern.
The signal would be tapped at the coaxial interconnect between RF Unit and Main Unit - Just like the PTRX-300 instructions. It would also require a connector rework - The PAT board features u.FL connectors, and the signal tap comes from the SP Coaxial Cable.
Well, that's it - This is a brain dump about the IC 7300 feasibility of this Panadapter - Good luck!