[time-nuts] Long wave receiver ideas

Murray Greenman Murray.Greenman at rakon.com
Wed Jun 24 15:07:40 EDT 2009


Marc,

I endorse Leigh's suggestion. It is a very simple but effective
solution. I use the SA602 myself. Used with an active whip antenna
sensitivity is not a problem, and you can receive signals from around
the world.

As for the local oscillator, yes you can most certainly use the FE-5650A
or FE-5680A, but I don't think that's necessary. If you have a receiver
which has suitable stability and can receive 10MHz, then a very good
solution is to drive the S602 with a 10MHz OCXO as the LO (the SA602 is
very accommodating, and can act as VFO, XO or buffer for an external
LO), or even drive it from a 10MHz GPSDO. Bear in mind that any phase
noise or modulation will appear on the mixed output (and 1Hz modulation
can be a problem with GPSDOs if you're not careful).

There is a very neat technique which works well below about 500kHz to
give extreme precision to reception. This is 'Clicklock' developed by
Peter Martinez G3PLX. Essentially you can receive any signal which has
ultra-low drift even if your receiver or converter has drift. It uses
harmonics of a 1pps reference compared with the 1pps pulse itself to
compensate for receiver drift, and all you need is a 1pps GPS signal and
a PC with sound card. The software is then able to provide sufficient
phase stability to integrate the received signal synchronously over many
seconds, giving incredible sensitivity and bandwidths measured in
milliHz. It has enabled me to discern the carrier (and hourly phase
advance) of WWVB on 60kHz at a range of 8000km, and for my own 80uW EIRP
transmission on 181kHz to be detected 500km away. See
http://www.qsl.net/zl1bpu/ZL2AFP/CLICK/click.htm for more information
and Clicklock software by Con Wassilief ZL2AFP.

73,
Murray Greenman ZL1BPU





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