Paul,
Thanks for that detailed explanation. I've done something similar for MARS
but of course higher frequency and that was transmit also.
I've seen the site of something similar but I think that was a 3' diameter
design; and I've looked at some of the Symmetricom schematics I've
been able to
Ray lots of people have worked the hardware approach. The hill to conquer
is the software version. To me that means far few things to solder. That
means more people might build it.
With respect to the antenna a simple Fet follower is very good. We all like
to use opamps but its overkill. Whats
Direct IQ demodulation to zero-IF is indeed subject to problems from LO
leakage into the
mixers. Said leakage will displace the center of the IQ plot away from the
origin, which
then requires correction later on, which is a pain to do well.
A pretty good way to deal with all this is to
Hi
I don’t believe that the WWVB transmitters change power day
to night. Both the north and south antenna’s are fed with the same
power, regardless of the time of day…..
Bob
> On Oct 9, 2020, at 5:59 PM, rcb...@atcelectronics.com wrote:
>
> Paul,
> I was seeing a -10 dBm on the SA when they
Hi
This is Time Nuts. All we have is the information provided by various members.
They describe their antenna setups. Again, anything in the > 100’ range for a
WWVB antenna is something I would call “massive” compared to a <1’ long rod
antenna.
Bob
> On Oct 9, 2020, at 5:02 PM, John C.
Have built whips and small loops and ferrite cores of various sizes. For me
the best is the 10' by 10'. As mentioned earlier in the thread as measured
on a dymec receiver. Other solutions during the day 10-30uv. Large loop
60-200. Night is just crazy up in the millivolt range. But not all of the
Paul,
I was seeing a -10 dBm on the SA when they enter high power mode at
night. At low power they are only a couple of dB above the nearby noise
makers. But that is at the output of the last stage of my receiver. The
WWVB signal was about 10-15 dB above the noise makers in my work shop. I
don't
John I don't think so as not sure how many have built a large antenna.
Certainly any of the old wwvb receivers have details and thats pretty much
what most people copy.
Essentially a 3 foot copper loop with numbers of turns of wire connected
together. Like 25 pair telco cable connected end to end.
The NIST WWVB transmitter antenna is very massive and very well documented:
https://apps.dtic.mil/sti/pdfs/ADA299080.pdf
For receive on VLF there is no reason to go so big. A short whip produces
plenty of atmospheric noise so there’s no purpose at going bigger. A loop
(including ferrite core
Bob,
Thanks for the answer; but does anyone actually have a documented
specification posted for one of these 'massive' WWVB 60kHz antennas
someplace?
Thanks.
73's,
John
AJ6BC
On Fri, Oct 9, 2020, 08:35 Bob kb8tq wrote:
> Hi
>
> At least to me, anything dimensioned in the 100’s of feet is
Hi
Since you need a MCU to decode the data, you might as well get
things in there sooner rather than later. There are a number of MCU’s
out there that have fast enough ADC’s to do the job. They do have limited
dynamic range. You can go to one of the 24 bit converters and have
a ton of dynamic
OK then that would be a classic TRF receiver. Very typical be it
transistors and coils or opamps.
Whats the level on the SA?
Now you have entered the nasty territory that can give you many hours of
fun. The nast BPSK signal. Look at google for BPSK and costas loop
techniques. That will give you
Hi Bob well at 140' and 60 KHz its not a long way away from the receiver.
But good enough to allow development and testing. :-) I have not had
feedback from the antenna. Though sometimes I do wonder when wwvb is
several millivolts at night. The modulation is still there but that is a
lot of
after the bpsk is removed true. I have done that. A simple RC filter and a
100K over 50ohm divider to get the signal to a reasonable level. Add a
coupling cap because all of the old receivers output a preamp voltage.
On Fri, Oct 9, 2020 at 11:35 AM Bob kb8tq wrote:
> Hi
>
> For a full setup,
Paul, Bob,
I am not using any commercial receiver. I am building everything from
scratch. The RF front end starts with a ferrite rod antenna feeding a
differential first op amp followed by 5 stages of op amp filtering and
amplification. When the last stage is fed to my spectrum analyzer
(through
Hi
At least to me, anything dimensioned in the 100’s of feet is “massive” compared
to
the rod antennas normally seen in WWVB use ….
The other point being that if the antenna is some sort of large loop, it’s
going to be
a good long ways away from the receiver. You get both a larger signal
Hi
For a full setup, you could do it a lot of ways. A setup of:
Antenna -> front end -> ADC -> MCU -> D/A would be one approach. Various
bits like a local clock also would get into the design. There are *many* other
approaches.
==
There are a lot of D/A’s that will clock in the 100’s
Hi Hal
I think your asking for an A/D if this is a receiver.
I can speak to the front end.
In the the US the signal in the east is some 10-60 uv during the day.
To leverage the full scale of the A/D that has to be amplified to the A/Ds
full scale. Say 1-2 V.
Thats easily some 90DBv of gain. So a
Seriously nice 1mv yikes! Big antenna. I used the small loop antenna
some2-3 ft diameter. In Ma. that always was something like 10-30uv during
the day. Now with a 10' per side square loop its a solid 60-200uv per day.
Night always goes way up even to the 1mv and higher level.
I am also challenged
Bob wrote:
> You could also say that with a longer accumulator, you get a closer
> approximation to a desired waveform.
The width of the accumulator does improve the waveform, but only if you need a
frequency between the
ones possible with the more narrow accumulator.
It goes
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