- IC706 ( the 'old' one, no MK2, with 270 Hz filter):
   Very deaf on 136kHz, no matter if the preamp is on or off.
   Turning the VFO knob OR THE VOLUME CONTROL results
   in a hissing sound, which stops after the motion.
   Looks like the rig picks up some noise from its own serial interface
   between the front panel and the microcontroller !
   Hopefully the IC706 MK2 ( & -G) are better at 136kHz.
   At 77kHz, I cannot even hear the DCF time signal transmitter near
   Frankfurt...

  Wolf  DL4YHF.

Wolf seems to be unlucky with his IC-706. I have a Mk1 which is a little
deaf on 136kHz, but adding a one-transistor pre-amp makes it a very good
receiver. I experience no interface noise when using the outside antenna,
though a few years ago when I did a lot of  73kHz portable work, I noticed
that the front panel display radiated LF for a few centimetres. The
synthesiser on the 706 is excellent and during last winter's transatlantic
tests it stayed within 0.1Hz for hours at a time, and once it was calibrated
with Argo and BBC 198kHz it could be re-set reliably day after day.

Mike, G3XDV