Category Archives: How To

Build a Raspberry Pi-powered SDR

Many thanks to SWLing Post contributor, Jeremy Clark (VE3PKC), who writes:

I have developed an SDR receiver that may be of interest to your readers. It can be used directly with the Raspberry Pi2B/3B. It comes in several versions DIP/SMD.

Check out this MP4 movie:

I have two eBooks which are basically design manuals for the DIP and SMD version of my SDR receiver. Each eBook has an Internet linked parts list, so that the reader can get their own parts to keep costs down. The DIP eBook is $7.90 CAD and the SMD book is $14.90 CAD.

Click here to view Jeremy’s website.

Thank you, Jeremy–this looks like a fascinating construction project!

Readers: just to be clear, Jeremy is selling eBooks detailing construction–not kits. He did mention if you’re interested in obtaining the PCB, he can sell this as well.

Guest Post: Richard builds a WiFi radio with the Raspberry Pi

Many thanks to SWLing Post contributor, Richard Schreiber (KE7KRF), who shares the following guest post:

Yet Another Internet Radio!

by Richard Schreiber (KE7KRF)

After deciding that an internet radio could be an important source of entertainment in our household, we formulated a few general guidelines:

  • We opted not to use an aggregator but would pick and choose stations we enjoyed and discover the URL’s ourselves. Also would be satisfied with a couple of dozen stations. Based on a recent decision to pare down the number of TV channels we were paying for, having access to hundreds of stations seemed impractical and unnecessary.
  • The price had to be affordable, thus eliminating many stand-alone, commercially available internet radios.
  • We already owned a quality portable speaker (Bose SoundLink Mini) so the internet radio didn’t need to duplicate that component.
  • Didn’t want to tie up nor be tethered to a laptop, tablet, or netbook. We predicted that would eventually lead to less and less use of the radio.

After some research, coupled with the fact I already had some experience with Raspberry Pi computers, that small device appeared to be our best choice. I had recently purchased the newer 2 B model, which has plenty of computing power, and had installed Ubuntu Linaro as the OS. (As an aside, this OS has not to my knowledge been upgraded for the latest Raspberry Pi 3). There are several other operating systems that will work just as well including the official Raspbian OS available through the Raspberry Pi Foundation.

I installed the MPD music player daemon and its client MPC, which is used to add to and delete station URL’s from the playlist, control volume, etc. An important find was the iPhone app called MPod which provides remote wireless access to the features of MPC. At the moment it is a free app for the iPhone (in my case the iPod Touch).

For portability, my Raspberry Pi is being used “headless”, meaning it is not connected to a monitor, keyboard or mouse. If maintenance is required you can use PuTTY, a SSH and telnet client, wirelessly from a Windows (or MAC?) PC, using a command-line interface. Mainly this is needed to shut down the Raspberry Pi properly before turning off the power, but it boots completely on its own when powered up. The MPod app will then load the playlist of stations and let you start playing the radio without direct access to the Raspberry Pi.

The sound output of my Raspberry Pi is connected to the auxiliary port of our Bose SoundLink Mini Bluetooth speaker. But instead of trying to implement Bluetooth on the Raspberry Pi, I took the easy way out and use a direct connection. The sound reproduction from this setup is very good, though audiophiles might be somewhat more critical.

The above represents a minimal investment if you already have a good speaker on hand. It does require some on-line research and learning at least enough to install the OS and software. The good news is that there are many websites and forums providing step-by-step instructions and helpful hobbyists willing to explain some of the more cryptic aspects. A few of the websites that I found to be helpful:

A couple of these also explain how to add a display to your Raspberry Pi internet radio.

Our Raspberry Pi radio is on each evening and has been trouble free. It is worth mentioning that this is a very portable setup, and can even be powered by a battery pack (the kind used for recharging tablets and cell phones) for a few hours. Of course you need to be near a wifi hotspot.

Thank you, Richard! What a great way to use the inexpensive Raspberry Pi. I have a spare Pi2 and an amplified speaker here at the house. Though I don’t need another WiFi radio, it would be fun putting this little system together. 

Video: Gary DeBock’s “Baby FSL” antenna

Many thanks to SWLing Post contributor, Gary DeBock (N7EKX), who shares this video and notes the following on YouTube:

This is the new 3.5 inch (89mm) “Baby FSL” antenna, designed to provide a powerful DXing gain boost for Ultralight radios (or any other portables) despite its very small size. It has 32 Russian surplus 140mm x 8mm ferrite rods and 31 turns of 1162/46 Litz wire. In the demonstration video it provides a daytime DX gain boost for 750-KXTG (Tigard, Oregon, 50 kW at 160 miles) from inaudible up to about S7 on the Eton Traveler III Ultralight radio.

Click here to view on YouTube.

Gary is certainly a first-rate DXer and an ambassador of our radio hobby. Gary shows us here that, with a little ingenuity, we can take a $50 radio and turn it into something exceptional! Homebrewing at its best.  Thank you, Gary!

Also, I had never considered that a high-gain FSL antenna would require very precise placement of the receiver for proper inductive coupling. It makes sense, though. This loop is tuned for razor-sharp precision!

Some day, when I have a little free time, I’m going to build one of Gary’s FSL designs.

Tecsun PL-310ET Memory Reset

Many thanks to SWLing Post contributor, Mike Ladd (KD2KOG), who writes with a Tecsun PL-310ET tip:

Happy Holidays! I found this trying different button combos on the PL-310ET. I don’t think this is documented online.

Tecsun PL-310ET Memory Reset

  1. Power off the radio
  2. Press and hold the Del key.When the radio beeps release the Del key.
  3. Press and hold the Del key again. When the radio beeps a second time hit the power button. All the station memories will be erased.

This should work on most of the Tecsun radios.

Very cool! Thanks for the tip, Mike!

BBC Research Department Report on the beverage antenna

Many thanks to SWLing Post contributor, Kris Partridge, who writes:

[R]esearch on DTH satellite TV service took me to a public website which is an archive going back to 1934. And boy, there is so much information there ..!

So what I pass to you for the Blog is this one as a start:

Knowing that many of your readers/contributors have made mention of using Beverage antennas I think this may make interesting reading. The report describes a method for accessing the performance of a Beverage, long wire, receiving antenna using off-air HF broadcast signals.

[…]It looks like the lower the better. And yes, there’s some heavy maths formula in there ..!

Wow–you’re right, Kris! This is very useful information. I’ll skip the maths bit and just follow the advice! Thank you for sharing.