- Many HF rigs are deaf on 136kHz, for example the FT817, although this is less deaf if you switch IPO to "on" on 136kHz. A small preamp may help as long as this is selective and doesn't increase overload and intermod from strong out-of-band stations.
- The receiving antenna may have to be directional e.g. a small loop/preamp to allow local noise sources to be nulled.
- DCF39 on 138.830kHz sending FSK data with a burst every 10 seconds is a good indicator of receiver performance: it should be a good strong signal in the UK.
- Ultimately it is S/N rather than noise figure that matters on this band.
- Be prepared to use PC software such as Spectran or Argo to look for weak QRSS mode signals.
30 Sep 2010
Several people have emailed me about receiving signals on 136/137kHz. Now I'm certainly not greatly experienced in this, but a few things I've picked up from others are worth passing on: