[time-nuts] new WWVB BPSK dev board

[Bob kb8tq]

Hi

Given the large “fade” of WWVB over a 24 hour period (it’s not always ground 
wave ….) most decent receivers in the past have run a front end with AGC on it. 
Indeed 24 bit ADC’s ( > 16 bit ENOB)  are out there for not a massive amount of 
money.  

It is a bit unclear just how much fade you need to compensate for until you get 
past the “that’s enough” point. There are a number of nasty points in the country 
you would need to check out. Since you also are trying to deal with an enormous 
amount of “crud” at the same time, there may not be an exact answer. 

Bob

> On Dec 4, 2018, at 4:48 PM, Attila Kinali <attila at kinali.ch> wrote:
> 
> On Tue, 4 Dec 2018 13:12:48 -0800
> jimlux <jimlux at earthlink.net> wrote:
> 
>> I maintain that it's the lack of a cheap RF front end that is the sticky 
>> point.
> 
> Doing a 2-3 stage transistor based amplifier should give the signal
> enough gain to be sampled with the ADC of a uC. I have such a design
> sitting around, that I did a couple of years back for DCF77, but never
> got around to actually built it (see attachment). 
> 
> It is meant to be run from 4V, so that one can use an unstable/noisy
> 5V source with an 4V LDO and should give ~70dB of total gain. I used
> BC547 in the simulation, but any NPN with decent h_fe and f_t should
> do (eg 2N2222, 2N3904,...). The 2N5484 is a bit harder to replace,
> as I selected it for its low V_th and narrow specified V_th range.
> 
> All that is needed for this to work is a tuned antenna, ie a ferrite
> rod with a capcitor on it that is approximately tuned to 60/77.5kHz.
> 
> 			Attila Kinali
> 
> -- 
> <JaberWorky>	The bad part of Zurich is where the degenerates
>                throw DARK chocolate at you.
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