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ANTENTOP- 01- 2018 # 022

RF Sniffer



For this case I made the second version of the LED RF Sniffer that was differed from the first one only by L1. L1 was air wounded, had 9 turns of 1- mm wire (18- AWG), length of winding was 40- mm and OD of the L1 was 28- mm. Small whiskers in 28- mm length were connected to the ends of the inductor. Figure 4 shows the schematic of the modified RF Sniffer.


Now it was universal RF Sniffer. It may catch RF from cell phone when the whiskers were near the antenna. To catch usual HF RF the whiskers should have length 1 meter and more- it depends on power of the transmitter and location of the transmitting antenna outside the shack and location of the LED HF RF Sniffer in the shack.


However, the most interest for me was to check the RF current on the outer braid of the antenna coaxial cable. When the RF Sniffer was inserted into RF Choke that was wound by the coaxial cable (the choke was placed near my transceiver) the LED was glow (when key was pressed) on the band where SWR was more the 1.5:1. It allowed me visually control transmission and took attention of my Cat to the blinking toy (he often try steal it when the LED is blinking). The RF Choke contained 5 turns and had ID 30- mm. So the L1 perfect fit the RF Choke.


Oh, yes, you may ask me why the PCB of the LED RF Sniffers had such strange form. It is simple. I would like made a perfect design and place the LED RF Sniffer into cabinet. For UHF RF Sniffer I want to use an empty box from SUPER WICK. For HF RF Sniffer I want to use an empty container from medical pills. But... then I leave things like it is...


73! Igor, VA3ZNW





Figure 4 Modified RF Sniffer with LED as RF Indicator



LED HF RF Sniffer



HF RF Sniffer Inside of RF Choke

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Last Updated:

January 3, 2020 21:24