Wednesday, April 14, 2010

IBP Beacon Superhet-RX XTALs

IBP beacons are nice and easy propagation indicators. With dedicated single frequency receivers, a nice propagation alert system could be built. Basic idea here, detect Morse-code and signal strength by means of micro-controllers, transfer this information to a PC and upload it to a web-page (e.g. grabber).

For coverage of all bands, 5 receivers would be required. Again I was thinking of the N3ZI boards, which would need pairs of crystals. Some back and forth thinking and looking at numbers, I was able to find pairs of well available crystal pairs. The suggested IF would be represented by the lower frequency (better ladder-filter) or cheaper crystal.
This is what I came up with: (suggested IF / suggested LO)

20m (14.100MHz)
  • 4.096MHz + 10.000MHz
  • 2.097MHz + 12.000MHz

17m (18.110MHz)
  • 8.000MHz + 10.106MHz

15m (21.150MHz)
  • 6.144MHz + 15.000MHz
  • 8.867MHz + 12.288MHz

12m (24.930MHz)
  • 14.746MHz + 10.180MHz (*)

10m (28.200MHz)
  • 4.194MHz + 24.000MHz

(*) 10.180MHz is a crystal found in 22 channel CB-radios.

Now, lets hope that the PCBs are a success, and a fully automatic propagation alert system will welcome the upcoming solar cycle.