[time-nuts] wwvb d-psk-r updated general purpose reciever

paul swed paulswedb at gmail.com
Fri Nov 1 16:04:01 EDT 2013


Hello to the group. It has been a while since I have sent anything. The
last was the wwvb regenerator for time clocks.
However I have been working on a general purpose wwvb receiver. One that is
inexpensive, uses parts available today, is inexpensive, single supply, low
power, and uses parts I don't need a microscope for. There are lots of
older designs out there and at least one quite nice design is by one of our
fellow time-nuts that started me thinking. But many of the designs use
inductors that have become difficult to obtain.
As much as I would have loved to hack one of the one chip wwvb clock chip
wonders they simply did not work out. They are hot receivers actually
because there was no way to pull the amplified wwvb signal out. Tried a
number of schemes like 2 chips in parallel. One detecting the AM signal and
providing AGC control to chip 2 that had no AGC or demod caps.

The design here is hot enough 8 uv region. Draws far lower current than the
IC versions I have built using opamps at least 1/10th. Has AGC and can hold
a range up to 1000 uv without distortion. Thats the highest I have seen
near Boston recently. The design is quite classic.

Uses J309 FETs and 2n3904 transistors. The two exotic parts are mouser IF
transformers and in reality the pesky 60 Khz watch xtals. 25 for $6 as I
recall. What I learned here is that they must be very lightly loaded to
allow a parallel cap to tune them to 60 Khz. They are sharp and that may be
the hardest part of the whole receiver. Easy if you have a sig gen. I will
bet quite tough if you try off air.

[image: Inline image 1]


There are several buffered outputs for general use. I have added one of the
8160b analog decoder to give me the old AM signal data useful for the
initial PSK search. There are two limiters being tested right now. The
MC3356 and the AD806 to give a very hard clipped carrier.
Both signals will be used for the next step of development in the d-psk-r
and that is a digital approach to correcting the phase shift changes. Any
way this goes this is the base receiver for me from now on.
Even if the digital approach never works I can add in the digital costas
loop I have shared and maybe one day the full analog costas loop that gave
me so much trouble and that the digital costas loops has given me a serious
clue to.
Regards
Paul
WB8TSL
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