---ZS Link Network Blog, Mossel Bay, South Africa ---: Modifying your RTL2832U

Tuesday, October 12, 2021

Modifying your RTL2832U – E4000 SDR dongle to reduce interference

I put my RTL2832U - R820T SDR into a metal case, this and a few other components redused interference significantly. This is what I did.

I was getting interference reflected on the SDRSharp console that I believe was coming from the computer. I used a 2.0 USB powered hub to give the SDR some distance from the computer, and I also installed some ferrite beads, but I was still getting some interference, I did try different power supplies for the USB hub, but the interference stayed the same, so I decided to put the SDR into a metal case.

Before installing it into the metal case I removed all unnecessary components which included the antenna connector and USB plug. (See image)

PLEASE NOTE: Before you start soldering any wires to the dongle ensure that you know the sequence of the USB wires i.o.w. 5v+, ground, D+ and D- as it differs from dongle to dongle. I am not liable should you connect the wires the wrong way around.

I installed ferrite (choke) baluns on both the USB GND and USB 5v+, the USB D+ and D- wires are twisted together like Network wires, there is a 1M Ohm resistor and 47nf ceramic disk capacitor between the USB wires shield and the metal case.

The capacitor can be a few different values, 0.01uF / 10nF / 10000pF to 0.47uF / 470nF / 470000pF / 0.0047uF / 4.7nF / 4700pF, but the resistor stay at 1M Ohm. I used the 47nF ceramic capacitor and it is working fine.

I installed a BNC Connector as the antenna socket. This is what I had on hand. I am sure that there is a better connector type but the BNC works fine for my purpose. The metal case was sourced from a local store in town for less than R25.00. I know you get far more fancier but also more expensive. This one did the job.

I use SDRSharp the latest Windows version but also tested GQRX on Linux. Both programs works fine.

I am not saying this is the correct way of getting rid of interference, and it seems like discussions on RFI and grounding are countless, I am just saying that this worked for me, and the info might help others.

Finally: Different radio bands experienced different levels of interference, the ones I use are the 2 Meter the 70cm band and the FM radio band. Unfortunately this project started a few years ago and was left dormant until a few days ago. Unfortunately I never saved interference images from the past to compare with the current images.

Looking at the waterfall I am happy with the end result and with less interference I am now able to use this cheap SDR Dongle to monitor the GRHub Network RF Link without having to sacrifice an HT radio for this purpose.

PS. This is not a neatly build project, looking at the hot glue and bad alignment of the dongle PCB. I again say I used what I had on hand as I needed to complete the unit a.s.a.p.