PiTX QRP TX Shield for WSPR on 20M Now For Sale

Back in October 2015 we posted about a piece of software for the Raspberry Pi called PiTX. PiTX allows you to turn your Raspberry Pi into a fully functional RF transmitter. When combined with an RTL-SDR a full transceiver radio can be built using the QTCSDR software.

PiTX works by modulating the GPIO pins on the Pi in such a way that it is able to produce FM modulation. The major problem with using this method of producing radio is that it creates large amounts of harmonics and interference outside of the intended transmit frequency. Interference like this is illegal and could potentially disrupt life critical radio systems such as emergency services, cellphones and air traffic control.

In order to cleanly transmit with PiTX an output RF filter should be used. Recently, the team over at TAPR.org have released a 20M WSPR TX filter shield. WSPR is pronounced “Whisper” and is short for “Weak Signal Propagation Reporter Network“. It is a type of amateur radio signal that can be broadcast and received around the world by using very low transmit power. Radio amateurs use it to see how far their signal can travel when using very low power (QRP) and to investigate signal propagation conditions. 

The 20M WSPR shield sells for $20 at www.tapr.org/kits_20M-wspr-pi.html.

The WSPR shield sitting on top of a Raspberry Pi.
The WSPR shield sitting on top of a Raspberry Pi.
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Could this also be used on 10 meters?

Pablo Lewin

one week ago I thought a Raspebrry Pi was a dessert! (I like apple pie!). Nobody explained to me that it is a normal computer just like your Mac or PC . You can use it just like a windows PC to browse the internet, write an email etc….The concept is as follows 1) you buy it and you plug a monitor, usb mouse and usb keyboard. 2) If the Micro SD does not have the OPERATING system (Like windows or OSX in MAC but for this contraption it’s called NOOBS/Raspbian and you go get it at https://www.raspberrypi.org/ and copy it into the MicroSD which is also the hard drive/ram ) After installing the operating system then it will work like a NORMAL computer with everything including the built in WIFI,THEN you go to https://www.tapr.org/kits_20M-wspr-pi.html and buy their “shield” (a little board than filters out all freqs except for the 20 meter band) you install it, connect an antenna cable to it and then you go back to the keyboard and mouse and open DOS 2.0 like window on the raspberri Pi windows desktop (it’s not windows but it looks like a windows computer display ok?) and in that window you type the commands (written on the TAPR website) and this thing will start transmitting until you type Control C to stop it. Phew! I had to learn the concept all by myself but I got some high end help from Zoltan HA7DCD and John W9DDD. THE MOST IMPORTANT PART IS GET THE COMPUTER GOING FIRST! SO YOU CAN AT LEAST USE IT AS A NORMAL COMPUTER WITH WINDOWS AND WIFI AND BROWSERS AND EMAIL… then add all the ham stuff ..Actually for 35 bucks it’s an AMAZING computer for browsing, word processing and emails and more! I hope this helps (I wish somebody had given me the simple concept that a Raspberry Pi is a NORMAL computer and to get it going FIRST before I do all the fancy Ham Radio/Astronomy stuff..) Live and learn. 73 es QRV de WA6RSV!

Jim Ford

I am using the Whispering Raspberry TAPR for my RPi Vb3. It appears to work OK but I seem to get only 25mw out (that is 3.3 Vpp into 51ohms) with a 200 Mhz oscilloscope. Does anybody have any ideas why it is so low. The PS voltage is 5.1 from a 2.5 wallwart switcher. Also the open circuit voltage is 5.6 V pp which implies the output z is about 36 ohms.
Jim Ford (N6JF)

Kelly McNutt

Jim..could you contact me offline ..my call sign @arrl.net? need a little help getting my Whisper Raspberry TAPR for my RPi Vb3. going..would REALLY appreciate it…veteran at HAM..newbie with Raspberry PI 🙂
thanks 73 k8mcn

Kelly McNutt

just ordered the TAPR.org 20M WSPR TX filter shield..is there any guides online for a complete newbie to use this with my Raspberry PI…quite comfortable using WSPR with my traditional setup..ft950,signal link etc…but like most hams, wanting to try some thing cutting edge and new..and links or leads appreciated 73