Loop antennas

From my own results I think loops are (maybe) 6dB down on a dipole. This is far from accurate, but the losses are likely to be greater on lower frequencies and less on higher bands. 

This is 1 S point, so not too great. For some applications that do not require much frequency change they can be ideal. FT8, PSK31 and WSPR come to mind. 

When I had no external 10m antenna earlier in the year, I used an old Whizz Loop on 10m FT8. Although I may have missed some stations, I still spotted plenty. Mine was just on the shack windowsill indoors.

If you have limited space and can cope with them being very sharp tuned, if efficient, they can be a decent compromise antenna. With QRP you will not need special capacitors. With QRO the voltages at the high impedance points can be very high so special capacitors will be needed.

See https://sites.google.com/view/g3xbm4/home/antennas/loops .