Initial testing with the HackRF showed that it was being swamped with external RF from nearby transmitters. Approximately one mile from my home is a large transmission array which has a local radio stations transmitter which is outputting 2000W and also a number of other emergency service and other private transmitters which are transmitting on a wide section of the RF spectrum. Even with the antenna disconnected there was a lot of background noise and interference.
After searching online I found a company called NooElec who sell a HackRF One – RF Shield and Component Kit which they say helps to reduce stray EMI on the HackRF receiver. I ordered the kit and it arrived after a couple of weeks.
|HackRF One Case||HackRF One PCB||Kit Contents|
Installing the kit was very straightforward and after carefully opening the plastic case we soldered the RF shield outside frame to the pads on the PCB and then fitted the RF shield top.
The kit also included a ground clip test point which was soldered to the top of the PCB on the pad provided and also a 20 position female header which fits in the P30 location on the board.
|RF Shield Edge Fitted||RF Shield Top Fitted||GND Clip Testpoint fitted|
After fitting the shield we tried various frequencies to see if the noise floor was any lower but this didn’t appear to be different to when the shield was not fitted.
In the air band frequencies there was a small improvement on reception from the local airport (Bournemouth) but on the 70cm ham band (430Mhz to 440Mhz the interference from other local transmitters seemed to be the same.
We are now planning to make a custom metal case and a low noise switchable preamplifier for the HackRF One to replace the plastic case and we hope that the metal enclosure and preamp will improve the reception and external EMI noise issues.
|Header Socket fitted|