To add image rejection to the VK3CV tranceiver , i designed an add-on board which can supress the unwanted sideband by 17-20dB. But most important it also gives appx. 4dB better S/N ratio. In FM duplex mode the tranceiver uses both sidebands, so the board is having pin diodes to enable swiching between sidebands. The board measures 24x40mm and can be mounted vertically besides the antenna and it fits directly to J4 on the main board, other solutions is also possible.The board is passive and only requres 10mA to drive the pin diodes. The IF output is routed back to the main board, where IC4 is used to ampilify the IF signal. In that way your original mechanics can be reused as the IF is comming out on the same SMA connector.
I have a few blank PCB´s for sale, cost is 20 dKr./ 3 EURO + shipping, send me a personal mail to order.
IQcombiner V3 documentation: