[sdiy] ot: long wave radio reciever for time/frequency

[Czech Martin]

Just for fun I want to build a reciever for the 77.5kHz
German time/frequency standard radio transmitter.
Other countries have similar long wave frequencies.

I want to use a ferrite antenna.
For now I have 100 + 100 windings of 0.2 mm copper wire,
single layer. I want to see the difference between 100
and 200 windings.

-would it be harmfull to have a second layer? i.e. 400 turns?
 (I fear that winding capacitance might influence
  the resonance I want to build at 77.5kHz)
OTOH I want to have as much signal as possible.
I have read that in Zurich (Switzerland) the signal
can be as low as 100uV.

For the reciever I've found that external noise (athmospheric)
will be much larger then any amplifier noise.
So I could save here. Any opinions?

What do you think about the idea to divide the amplified signal
by 77500 in order to have 1 Hz square pulses?
I mean, the hope is that any noise will be averaged if I use
ripple counters as much as possible (the factorisation
is 2*2 * 5*5*5*5 * 31, why did they do that? 31, what an ugly prime, ...)
So I hope that in spite of athmospheric noise the
derived second will be quite exact, maybe in the same range
as a quartz osc. would be.

?


I think that filtering the noise via pll would perhaps have more
noise problems, (4046), unless I use an LC tank.

Since the antenna noise is so large, I could perhaps just use
a cascade of cheap op amps, to have a gain of 1000 or so.
Any bandwidth limitation should not be necessary,
and this would require LC filters (77.5kHz is hard to do
with RC active filters and Q>5 or so.)

?


Cheers

Martin Czech

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