Reducing USB Shield Interference on RTL-SDR Dongles
Leif, the programmer of Linrad has recently uploaded a video to YouTube showing how he shields his RTL-SDR dongles to prevent the USB shield from acting as an antenna and picking up unwanted signals. In the video he also measures how well various other SDRs are at avoiding USB shield interference.
From the video we can see that Leif’s shielding method uses the following steps:
- The metal box is RF tight and held together by many screws.
- The USB shield and external antenna connector shields are both connected to the box.
- The USB 5V line is decoupled to the GND line.
- The USB 5V line has a ferrite on it.
- The internal coax connection between the external connector and RTL-SDR antenna connection has a ferrite on it.
- The USB cable has a ferrite where it enters the box.
With this shielding effort the interference is significantly reduced.
I follow Leif on YouTube and what they don’t mention is he heavily shields his computers and other equipment that causes interference too. I recommend you subscribe to his YouTube channel. He really is a brilliant radio guy.
Now I could be wrong and I may be . I don’t think that I am getting any shield interference . How would a person be able to know if they had the problem . I live in a one floor house and I have put a ten foot ground rod out side the office were my computer is . A wire comes through the wall to a ground buss on the inside of the room it is not connected to house ground . I have the computer and MFJ 1020C connected to the ground buss .
I don’t get shield interference either, I just snapped a big ferrite core onto the usb cable and it took care of everything, after reading this though i might put one on my antenna, not sure if it would desense it though.
You can put all the ferrite cores you want on the cables. If the dongle itself isn’t shielded, it will still pick up RF from nearby sources.
2-3 cores on my USB cable reduced my noise floor by 10-15db. Incredible. Dongle is unnmodded NESDR SMART