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Author Topic: WSPR on 22 Meters?  (Read 243 times)

Offline N9QIW

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WSPR on 22 Meters?
« on: May 13, 2020, 0628 UTC »
Just thinking out loud here:    Has anyone played around with making a 22 meter WSPR transmitter? WSPR's 6 HERTZ bandwidth has me thinking, perhaps developing an Arduino based transmitter using an AD9850, Arduino Nano,  OLED,  etc. etc. Best, Alex.
Alex
N9QIW
Fresno, CA USA

Offline Dave Richards

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Re: WSPR on 22 Meters?
« Reply #1 on: May 13, 2020, 0750 UTC »
The Ultimate 3S kit from QRP Labs will do the HiFer band, if you use the LPF kit for 20M. As for the output power, the Si5351 puts out about 10mW. Looking at the schematic for the U3S, you should be able to omit the BS170 PA and take an output directly from the Si5351 output to the LPF. An attenuating pad could get you down to HiFer power level. Alternatively, if you use just one BS170 transistor in the PA, I'm wondering if you can adjust the bias pot R5 enough to get down to HiFer power.

Here's the link to all the info on the U3S kit -

https://www.qrp-labs.com/ultimate3/u3s.html

I built one a while back, for the ham bands, and it's a great little kit. WSPR would be a good way to go on the 22M band, as legal power is so limited. I wonder if anyone has tried having a 2-way QSO on 22M, using one of the new-fangled digital modes?
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(SF Bay Area)

Offline Prairiedog

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Re: WSPR on 22 Meters?
« Reply #2 on: May 13, 2020, 1912 UTC »
WSPR is a very viable option for 22 meters, Alex. as a search of the LWCA.org message board would reveal. It is roughly equivalent in detection efficiency to QRSS3, which is the "gold standard" for the band, but has greater data throughput per minute.

There are currently two stations active in that mode, K3SIW and K5LVB, another that uses WSPR intermittently (WA1EDJ), and a Canadian who uses the call J1LPB has been on in the past but hasn't been reported in quite some time.  All the currently and recently active WSPR stations employ an Ultimate 3s as the transmitter, with the output stage modified and/or an RF attenuator at the output to get down to the necessary power level.  There's a WSPR test generator kit being sold (I forget the name of it) that has been discussed in some forums which apparently has a suitable output. It's popular for 30 meter ham beacons, although I'm not aware of anyone actually using it on 22 m.

But the very first WSPR on the HiFER band was seven years ago from Jim Vander Maaten (former beacon ESA), who was generating it with a Raspberry Pi that he also used on 30 and 20 meters, if I recall.  He only ran it on 22 for something like a day and a half, unfortunately. During that time I could see it on an Argo screen, but I wasn't familiar enough with the WSPR decoder software back then to set it up for nonstandard off-ham-band frequencies. By the time I got the hang of it, he had abandoned 22 meters, so I had to wait a few more years until K3SIW put his WSPR beacon on the air. The article about the R-Pi that Jim mentioned back then is still on the Web:
http://soldersmoke.blogspot.com/2013/03/wow-raspberry-pi-as-rf-transmitter.html

As for other "new fangled" digital modes suitable for QSOs, Dave, it would sure be great to experiment!  PSK-31 has been tried, but its bandwidth was too large to be effective in this band, except locally. Slower versions of JT mode would probably be at least as effective as WSPR. But one significant problem is that no one currently offers a suitable exciter for real-time keyboard to keyboard communication on this band. So far, all the available and/or adaptable kits have been intended for beaconing, meaning they have to be reprogrammed each time the outgoing message changes.

Offline N9QIW

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Re: WSPR on 22 Meters?
« Reply #3 on: May 14, 2020, 0840 UTC »
Thanks for all of the replies.  I think the route I am going to take is:

1.a.  Edit/modify WsprryPi:  https://github.com/JamesP6000/WsprryPi/blob/master/wspr.cpp to include a 22 meter option, by adding the code:

else if (!strcasecmp(argv[optind],"22m")) {
      parsed_freq=13556100.0

1.b.  Delete all programming associated with the ham band WSPR, as this transmitter will operate unattended.

2.a.  Grab a Raspberry Pi Zero W from my inventory and load the modified WsprryPi code on it.

2.b.   Find a way to sync the clock/signal to GPS (using a GPS module from inventory) or another stable clock (worse case a DS3231 High Precision RTC).  I'll need this option if the Rasberry Pi is not in WiFi range to update from the NTP time servers.

3.  Build a decent low-pass filter (LPF). 

4.  Attenuate the signal down to below FCC maximum levels in concert with item 5 below. RF output from the Zero is stated as 10mw, so this shouldn't be too hard.

5.  Add a quick, down, and dirty 22 meter dipole antenna.

6.  Bench test it.

7.  Build an appropriate solar power supply/regulator with battery backup/solar recharge capability.

8.  I'll likely place this one at the family cabin in near Duck Creek Village (~5500 feet, low QRM, etc.) in Central Utah...and listen for it from Fresno, CA.

 







Alex
N9QIW
Fresno, CA USA