An evening project: W7IUV low-band receive preamplifier. Total cost: < $10. Total time: 1 hour.
It worked pretty well on 80 and 160 with the crossed K9AYs. The 48-volt relays in the box at the antennas are sticking (thanks to using a 40-volt PSU). I need to rebuild this with lower-voltage relays or a higher-voltage power supply.
W7IUV claims that he just leaves his connected to his RX port all the time. But, he probably has more spacing between his TX and RX antennas than I do. It will be interesting to see if I get enough RF coupled from my TX antennas to destroy the transistor.