[time-nuts] WWVB Simulator
zl1tao at gmx.com
Thu Jan 5 18:06:03 EST 2017
I came across this: " rpitx " it is python software that enables a
RaspberryPi to transmit using a GPIO pin.
The links refer to using the Rpi to produce 2m Tx signal. Rpitx seems
able to produce most modulation schemes. I have not tried it so have no
idea if it would produce your need directly.
On 01/05/2017 09:53 PM, M. Simon via time-nuts wrote:
> The design of the - wwvb cheatn d-psk-r - is an excellent start. It is why I wanted a WWVB simulator. There are some points that need improvement though. To cover the full range of a VCXO the current design might require (in theory) as much as a +90 to -90 deg phase difference between the local oscillator and WWVB. I thought that should be reduced to +22.5 to -22.5 degrees ( in theory - actual will be less because the VCXO I'm using is active from about .5V to 2.5V instead of the full 0 to 3.3V). So that adds a voltage reference (for the offset), op amp and offset resistors to the frequency control loop.
> I'm also doing full surface mount (designed for hand soldering) and rationalizing the parts values. A fast CMOS comparator (instead of the clunky LM311) etc. Power required will be +/-12V and +5. Local regulator(s) will supply parts that need 3.3V. I'm designing with low cost in mind.
> I still have a lot more work to do but the general outline is more or less complete. I will publish when I get some testing done.
> The AM detector is also not like any other I have seen. It may be overkill. But it is not very expensive.
> Engineering is the art of making what you want from what you can get at a profit.
> I like Polywell Fusion.
> On Wednesday, January 4, 2017 7:29 PM, paul swed <paulswedb at gmail.com> wrote:
> SimonLike you I tend to like hardware. But today complete micros are so cheap and powerful they make life easy. Heck a bit to complex use 2 or 3. I like to follow the "Get-er-done" philosophy.
> That said search the time-nuts archive for the wwvb cheatn d-psk-r. It knows how to create the bpsk time stream aligned to wwvb then flips a BPSK switch to remove the BPSK. This allows all of the old phase tracking receivers work without modifications.I used an Arduino $8 maybe and shared all of the details and software with the group. It preserves the old AM for radios that need that modulation.So a corrected wwvb signal can be had for cheap and it works very well here on the east coast. As well as wwvb ever did.
> Have fun and use whatever technology you like as you are the do-er, you get to choose.
> On Wed, Jan 4, 2017 at 2:48 AM, Chris Albertson <albertson.chris at gmail.com> wrote:
> You don't need to tie up a PC. It could likely output the WWVB
> signal while it was also surfing the web and reading emails. 60KHz
> is NOTHING compared to displaying a you-tube video
> In fact I bet your 48MHz uP could directly synthesize the signal.
> Look at the ratio of 48 MHz / 60 KHz. The uP can execute about 800
> instructions during one cycle of a 60 KHz courier. Your PC can do
> a million operations during that same one cycle.
>> Sure. I considered software. But I'm a hardware guy. I like designing boards. The rig was designed to do amplitude and phase simply. The final design will have a $5 48 MHz microprocessor included. I'm using that one because of speed and memory. When that proves out I might redesign for a $2 24 MHz processor. Onesies prices at Mouser
>> Besides the hardware better illustrates the concepts than software. And I don't have to tie up a PC if I don't want to.
>> I haven't priced everything out yet because the design is not done. I'd be surprised if the cost was over $20 in parts for everything - power supply not included. PCB extra.
>> Feel free to send this along to the list if you are inclined.
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