RF (Radio Frequency) is always something I wanted to know more about. My interests drove me to getting my ham radio license in 2012. Once I had it, I became aware of just how much I didn't know. Not long ago I learned about the RTL-SDR dongles which are intended for digital tv reception on computers. Fortunately, someone realized that they could receive a very wide range of radio frequencies (From ~24Mhz - 2.2Ghz, depending on which one you buy). Costing only $30.00 USD made it even harder to pass up.
Different dongles have different circuitry and therefore different ranges and performance characteristics. So be sure to research before you buy.
After installing SDR# on my windows pc and playing around with my dongle for a few days, I was already looking for ways to improve its performance. Specifically regarding stability and noise/interference reduction. I looked at what others were doing and also tried out some things on my own.
My first enhancements were removing the plastic case to help with heat and to disconnect the USB housing from the ground on the pcb board. Temperature changes on the circuitry affect the received radio signals and heat affects performance, so anything you can do to cool and stabilize temperature is beneficial.
I added some double-sided sticky foam under the usb connector to insulate and keep the usb connector rigid. These two modifications really helped keep the temperature stable and lower the background noise. Honestly, performing these two steps and connecting your rtl-sdr to a short usb extension cord (again to lower noise) should be enough for most users. Try just a short usb extension first since it is an easy step.
I also tried removing both the antenna and usb connectors and soldering to the PCB directly. This did help but not as much as the previous two steps. Here is the PCB with usb and antenna connectors removed.
Here is a waterfall output from SDR# showing a portion of the 900mhz band. It is what I used for all of this testing.
I ran the above setup for a few months and was able to learn a lot about the RF spectrum. I did want to explore lower frequencies below what my rtl-sdr could provide. Thankfully the popularity of this platform has prompted 3rd party companies to create and sell addons such as this NooElec upconverter that I purchased. Upconverters work by shifting the frequencies of received transmissions up and providing that output to the rtl-sdr. In my case the shifting is by 125Mhz up. Transmissions received at 100mhz (like a local radio station) would now appear as 225mhz.
Now I am able to access HF ham radio bands and other HF frequencies with my rtl-sdr. The reason 125Mhz was chosen was to avoid FM radio stations which are loud and cause interference.
I soldered my rtl-sdr directly to my upconverter and mounted them inside an aluminum enclosure to minimize RF interference. Here is what they look like with the lid removed.
I later trimmed the sides to make the whole enclosure smaller and easier to transport.
A standard F type connector was used due to the availability of cable and connectors. I haven't been in the hobby long enough to have a supply of bnc or other preferable connectors and cable. It will be easy enough to change later if needed.
A short usb cable with installed ferrite core further reduces RF interference and a switch allows me to turn on or bypass the upconverter.
The completed enclosure with lid.
If you liked this, you will likely be interested in my other rtl-sdr posts that you can find here: rtl-sdr tag