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

[John Ackermann N8UR]

Hi Scott --

On 3/12/24 20:44, Scott Newell wrote:
> At 09:57 PM 3/6/2024, John Ackermann N8UR via time-nuts wrote:
> 
>> 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.
> 
> Do you happen to know if it's too late to get in on this? And if 
> totality is required? (My QTH will only be 99.997%, but work will be in 
> totality for 3:44. Steel building and no easy window access for an 
> antenna, though.)

There are two or three different activities going on. One uses dedicated 
receivers called "GRAPES" while others use the wsprdaemon network I 
mentioned.  You can participate no matter how close you are to totality 
-- the ionospheric effects extend over a pretty large area.  'm not up 
on all the details but the https://hamsci.org site has a bunch of 
information on all of this and I'd suggest checking there.

There is one specific project for stations right on the path that are 
doing CHU measurements.  That may require some special hardware.

The HamSci annual conference is next weekend and I *think* but am not 
sure it is being streamed via Zoom and/or YouTube.  There will be lots 
of stuff about the eclipse experiments there.  Again, the website has 
info about that.

>> 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
> 
> (Sorry to pile on with the questions...) This looks very exciting, but 
> I'm concerned I might not have any PCs fast enough. Everything I've read 
> just mentioned recent i5/i7, which is suitably vague. Any idea if  > are benchmarks for guidance as to should work/might work/won't work?

[ snippage ]

A lot depends on just what software you're using.  The challenge isn't 
as much CPU as being able to handle the USB pipe, which is something 
like 2 gigabits for 32 MHz bandwidth.  The fancy GUI based receivers 
might take a lot more horsepower, but I've run the RX888 with ka9q-radio 
at 64 msps (32 MHz bandwidth) on an Orange Pi 5 and similar SBCs like 
the RPi 5 should work.  The RPi 4 is probably just at the edge.

There are many wsprdaemon stations monitoring multiple bands that use 
tiny-form-factor PCs with 6th-ish generation i5 mobile processors.  I 
have a little Lenovo i5 that was about $125 from a liquidator.  The 
RX888 server process by itself uses about 2/3 of one core.  Virtual 
receivers that tap into that bandwidth use almost no additional CPU 
(though whatever is consuming the data might).  And, with multicasting 
you can have receiver processes on other computers on the LAN.

Did I mention that it's cool? :-)

John