[time-nuts] Long Wave Receiver ideas
Murray.Greenman at rakon.com
Thu Jun 25 14:39:43 EDT 2009
Regarding Clicklock. Yes, in a sense Clicklock is a lock-in amplifier.
However the really special thing is that it completely compensates
(within reason) for the drift in ALL the oscillators in your receiver
and/or converter, so that it becomes GPS locked. It does this by
comparing the phase of harmonics of 1pps as they arrive at the receiver
with the phase of the 1pps itself. It uses an NCO to down-convert to
zero Hz. There is obviously an advancing phase with frequency in the
1pps harmonics if the down-converted frequency is high, and the NCO is
shifted to compensate.
It will also therefore also compensate for changes in phase and delay
through the preamp, feedline and receiver filters.
If you look at the examples on the reference I gave,
http://www.qsl.net/zl1bpu/ZL2AFP/CLICK/click.htm, you'll see there's a
phase plot which shows the integration of I and Q samples, plus phase
and power plots which are achieved by maths from the I and Q followed by
'leaky integrators'. That bit was my contribution. The whole idea
originated with Peter G3PLX, the source of many good ideas.
Give it a try - it's quite a tricky bit of software to drive.
Murray Greenman ZL1BPU
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