[time-nuts] Re: SDR radios - Loran-C & WWV

[John Ackermann N8UR]

On 3/6/24 17:45, Tom Van Baak via time-nuts wrote:

> Stable32 image attached. After all that hassle, I made a mental note to 
> add SDR to my Christmas list. ;-) It sounds like someone could make a 
> cool 24x7 logging project using all the WWV frequencies, dynamically 
> tracking amplitude and phase, etc.

WWV tracking (and CHU as well) is a major experiment in the HamSci 
(https://hamsci.org) community, where they've built low-cost hardware to 
monitor multiple WWV frequencies simultaneously.  There's a major effort 
lined up to get data from hundreds of stations during the eclipse on 
April 8.

SDR is a whole new rabbit hole to run down.  We're on the cusp of a 
shift from radios that listen to a few hundred kHz ate a time to what we 
used to call just "software radio" -- an ADC that sends high resolution 
wideband data to the PC and lets the processing happen there.  USB3 is a 
fast enough interface to allow the full DC - 60 MHz spectrum to be sent 
in one giant firehose.

There's an ~$250 device called the RX888 that's available on eBay and 
Amazon that does this (no link because there are multiple providers and 
I can't vouch for any of them).  And Phil Karn has developed a 
completely new client/server based radio that uses multicast to allow 
many clients receiving hundreds of channels to connect to one receiver 
server.  Check out ka9q-radio at https://github.com/ka9q/ka9q-radio

This is still very much do-it-yourself land and the software is 
undergoing rapid development.  But what it can do is remarkable.

I run a remote receiver at a quiet rural location that uses the RX888 
and ka9q-radio running on an i5 class computer to monitor weak-signal 
"wspr" (https://en.wikipedia.org/wiki/WSPR_(amateur_radio_software) ) 
beacons on 10 bands simultaneously, as well as record WWV and CHU data. 
Our station typically reports over 50,000 receptions from ~1800 stations 
per day.

That data goes into a worldwide database that space scientists are using 
for propagation studies (examples: 
https://hamsci.org/article/wsprnet-data-used-validate-sami3-published-space-weather-journal 
; 
https://hamsci.org/sites/default/files/publications/2021_HamSCI/20210320_1700z-Gwyn_Griffiths_G3ZIL_Rob_Robinett_AI6VN.pdf 
; see also http://wsprdaemon.org).

And the receiver is clocked by a GPSDO, so it is time-nuts related. :-)

John