Daily Image
08-08-2022
Strong RFI source found nextdoor
| Submitter: | Tammo Jan Dijkema, Michiel Brentjens, Albert van Duijn |
| Description: | When testing new receivers at the antenna field, several RFI sources were found and eliminated. One of the sources took days to spot. The interfering signal consisted of spikes spaced 125kHz apart, ranging all the way from 125kHz to 100MHz. After doing thorough research, a possible cause for this RFI was found: the electric RFID lock of the telescope. This lock works on a carrier of 125kHz. But when looking at the signal with a scope, the signal is not really a clean sine wave (see inset on the bottom right). The spectra show one minute of data, where the vertical axis runs from 0-25 MHz (left figure), 25-50 MHz (second figure), 50-75 MHz (third figure), 75-100MHz (fourth figure). The door lock was switched off half-way the measurement, and on again near the end of the minute. A significant reduction in RFI is visible, while it is also clear that there is plenty of RFI hunting to be done. The solution to the leaking lock in the telescope was quite simple: the RFID lock now has a power button, so that it is only operational when someone actually wants to open the door. |
| Copyright: | - |
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