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

[John L Marshall]

Traditionally inductors for this frequency range were wound in several
pancakes. They look like lifesavers on a pencil. Yes, winding capacity
increases but you are tuning a single frequency. Use less capacitance to
resonate.

Have you considered using a PLL for the receiver?


Take care,
John
www.sound-photo.com
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----- Original Message -----
From: "Czech Martin" <Martin.Czech at Micronas.com>
To: "Sdiy (E-mail)" <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, April 02, 2003 1:24 AM
Subject: [sdiy] ot: long wave radio reciever for time/frequency


> 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
>
> CAD/CAE Library Group
> Micronas GmbH
> Hans-Bunte-Str 19
> D 79108 Freiburg
> Tel.: +49-761-517-2422
> FAX.: +49-761-517-2258
> http://www.micronas.com
>
>
>