I am pleased how well my old 1500, once pulled out of retirement, has worked on 575 kHz. However, both RX and TX need external lowpass filters. That a LPF is needed for RX broadcast rejection is no surprise. However, the transverter DDS TX output at f=475 kHz has a glitch at 2f, which causes no end of trouble further down the transmit chain. It is easily cleaned by inserting a pi-section filter with Q=1, namely with a shunt 6.8 nF, a series 17 uh, and a shunt 6.8 nF.