Portable SDR update

Friday, April 03, 2015
Update (15/11/16): this article describes my old portable SDR configuration. Jump to this post to see my current set-up.

This is a quick entry describing an update to my portable SDR setup. Readers may remember that my previous configuration suffered from the tablet's radio interference leaking into the FunCube Dongle Pro+ SDR. I solved the problem by using a galvanic USB isolator and a separate portable USB power supply for the dongle. When I posted this configuration on SWLing.com in August, Alexander DL4NO advised me that it's possible to get rid of the USB isolator. Because my balun has two terminals, he said, I can use it to make a dipole antenna (an antenna with two wires) that balances the radio current before it gets passed down into the SDR dongle, which ought to prevent tablet interference from getting into the antenna system.

At the time I wasn't sure this would work. His other suggestion — using a ferrite ring choke on the antenna feedline cable — didn't do much to suppress the tablet noise, which made me assume that it was FunCube Dongle's design that was at fault, and that the noise was getting in from the USB end and not via the antenna.

Wellbrook UMB130 balun
However, when I finally tried out Alexander's suggestion, I could not believe what a drastic effect the addition of the second wire has: as soon as I connect it to the balun, the noise disappears, even with the USB isolator "out of the loop". This simplifies my portable SDR configuration substantially. Below is a demo video:

There is no sound here because I was listening to Radio Australia's 12065 kHz signal using a pair of Bluetooth headphones. Note the low noise floor and the absence of any interference on the spectrum. This has a substantial impact on the overall cost:

1) On The Go USB host cable for Toshiba's micro USB connector: $7
2) FunCube Dongle Pro+: $186
3) Wellbrook HF Balun: $60
4) Feedline cables $7
5) 12 metres of thick copper antenna wire: $16

The total without the tablet comes to $276, and if you buy an HP Stream 7, you only need to add $90 more. A complete on-the-go SDR solution for $366 doesn't sound too bad, does it? Many thanks to DL4NO for making my set-up that much more portable!

About the author

This blog is written by a shortwave radio enthusiast based in London, UK. You can follow him on Twitter at @LondonShortwave


  1. Hi, what software are you running on the tablet?

    1. It's called SDR#, see my earlier post (linked above) for more details.

  2. That is pretty sweet. I have wanted to do this before, but wasn't really keen on spending that much money...I tried to do a much cheaper version by buying a $60 Android tablet and buying the RTL-SDR dongle, but that doesn't cover shortwave. This is definitely much much better than any portable, and it's a lot cheaper than a desktop radio. I like the idea of taking this anywhere though. Could you use an indoor loop antenna (like the Wellbrook ALA1530) with this setup?

    Thanks for your posts...I really enjoy your blog!

    1. I connect my tablet & FunCube DP+ to my home system that has a Wellbrook ALA1530 antenna. For example, see https://youtu.be/4qfYMw6jcG0 and https://youtu.be/IYXt7ldEex0 . But you will need a preselector such as Global AT-2000 (or Lowe PR150 / MFJ-956 if you want long wave). Otherwise the dongle will be easily overloaded by your loop output.