MARC - Cincinnati's Club For Amateur Radio - 147.345+

With Just a WSPR

By Dan Romanchik, KB6NU

It’s really amazing what you can do with computers in amateur radio, and there’s been an explosion in the number of digital modes. One interesting mode that I’ve recently been introduced to is WSPR, which is short for Weak Signal Propagation Reporting. The protocol and the original WSPR program was written by Joe Taylor, K1JT, and is designed for sending and receiving low-power transmissions on the HF bands to test propagation paths.

I won’t try to cover all the technical details here. There are several sites that cover them pretty well:
* Wikipedia: WSPR
* G4ILO’s Shack: WSPT – Distant Whispers

I was introduced to WSPR by my friend, Joe, AC8ES. He posted a message to our club mailing list asking if anyone had a toroid core that he could buy to make a QRP balun for 10 MHz. When I asked what he was going to use it for, he said that he was making a WSPR transmitter with a Raspberry Pi, and the balun was for the dipole he built for it. He said that he’d gotten roped into doing this because he’d attended a local Raspberry Pi users’ group, and when he mentioned he was an amateur radio operator, they encouraged him to try this project.

How could I refuse a request like that? I have a whole kit of ferrite cores, and after some back and forth, we found a small core that he could use.

The software he chose is WsprryPi . It’s described a “Raspberry Pi transmitter using NTP-based frequency calibration.” It uses a GPIO port to generate WSPR signals anywhere from 0 to 250 MHz. Joe said that there are several Raspberry Pi programs that run WSPR, but that he chose this one because it seemed to have more features than the others.

Figure 1 shows Joe’s setup. Since the output generates a square wave, a low-pass filter is needed to filter out the high-frequency components. As you can see, the GPIO output is fed through a 0.1uF decoupling capacitor into a Mini-Circuits 10.7MHz low-pass filter, then to a 1:1 balun, which is connected directly to the dipole elements.

Joe says, “The antenna is just a dipole taped up to the walls of my living room and hallway.” As you can see he made the balun and dipole from 24 ga speaker wire.

The performance of this setup has been kind of amazing. In one e-mail, Joe reported, “Your toroid seems to be working well. Got the balun and antenna finished and executed seven WSPR transmissions from the Raspberry Pi. The WSPR reporting website WSPRnet came back with a couple dozen reception reports; typical distance is ~300+ miles, max was 593 miles.” In a second e-mail, Joe writes, “Did a few more beacon transmissions and checked the WSPR signal reports again. Someone picked up my 5 mW signal from 1010 miles away in Canada.”

Joe’s turned into quite a WSPR fan. He’s even written an Android app – WSPRnet Viewer to retrieve and displays report from Tapping on a specific report displays more details about it, along with a world map that shows transmitter and receiver locations.

Unfortunately, I don’t have a Raspberry Pi, or I’d try this as well. I do have a BeageBone Black, but there doesn’t seem to be software that I can download and install as easily as the Raspberry Pi software. That being the case, this might be a good excuse to purchase one of those new, cheaper RPis.


When he’s not digging through his junk box or teaching amateur radio classes, KB6NU writes about amateur radio at KB6NU.Com. He has just released The CW Geek’s Guide to Having Fun with Morse Code. The book is available on Amazon.Com or on KB6NU.Com.

Calling MARC Casual Contesters

NCJThe next contest on the MARC Casual Contesters calendar is the North American SSB QSO Party, or NAQP, sponsored by the National Contest Journal. The contest runs from 1800 UTC Jan 17 to 0600 Jan 18. That’s a 12 hours window that runs from 1 PM EST on Saturday to 1 AM EST on Sunday.

What’s a casual contester? It’s someone that’s not in-it-to-win-it. If you can spend 30 minutes on the air join a team. This contest is a good one if your working on Worked All States.

Power is limited to 100 watts, so your not competing with the big guns. What can you work with 100 watts? Get on the air and find out.

We will be entering MARC teams for the contest. Teams consist of from 2 to 5 single operator stations, teams must be registered prior to the contest.

If you’d like to be on a MARC team reply by email before 10 AM EST on Saturday, Jan 17.

My first choice for logging software is N3FJP, however if you need logging software download N1MM Logger, it’s free. Contact me via email or on the MARC repeater if you need assistance configuring N1MM Logger. It’s an all in one contest logging program and can be a little overwhelming at first glance. Getting if configured for a single-operator station is easy and we could have you ready to log in less than 30 minutes. Just don’t wait until Saturday morning to ask for help.

Rules can be found at

Can’t find 30 minutes this weekend to operate, OK we’ll settle for 15 minutes. Goal is to get as many MARC members as possible listed in the results. You’ll see you call in print.

Bill WS6K
MARC Contest Coordinator

President’s Message for January 2015


President, Michael Kieffer, KD8OUT
Vice President, Ron Brooks AC8MA
Treasurer, Chris Spiess AE8TT
Secretary, Andrew Rohne KE8P

At the November meeting, the MARC BY- Law change was approved by unanimous paper ballot, with quorum and certified by the club Secretary to change term limits on club President:

At the November meeting the consensus was that we should have an upcoming vote on an additional change to the By-Laws to have the Club Board of Directors as the club President, Vice-President and a yearly elected board member from the membership at-large. Bruce Davis, AC8BT, was requested to frame this amendment into legal verbiage for a vote in an upcoming meeting. This change was made necessary by removing the term limits on the club President.

Our next meeting is 1/8/15 and the topic is “Log book of the World” – by Kitty Heavner. Kitty has requested a “volunteer” at the presentation to sign up for Log Book of the World as a real example.

We need suggestions for meeting presentation topics. Please email suggestions to

73, Mike Kieffer (KD8OUT), President

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