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RF power measurment in a band
resistor:
Hi all,
I'd appreciate any feedback on a project idea I've been noodling about. I have no experience working with RF signals, so I'm worried that I'm way off the deep end.
I happen to own a sail boat, and like a lot of sail boat owners I'm always worried about conserving battery when anchoring out overnight. A big trend in recent years has been replacing old 12v halogen lights with 12v LED modules, which saves a ton of power. However, a concern has been raised over shoddy LED modules potentially radiating RF in the marine VHF bands (156-174MHz), which could be a safety concern as VHF is your primary SOS facility on a boat.
What I want to build a simple detector to determine whether an LED module I have plugged in radiating within the marine VHF band. I need to build in the ability to set a baseline, since the amount of ambient energy in the band will depend on time of day, location, whether my neighbor is using his radio, etc. The idea would be to set the baseline, flip the light switch, and indicate if power in the band is now above the baseline.
So my idea currently is to attach an appropriate antenna to a band-pass filter for the 156-174MHz range. I think I then need to feed that through a logarithmetic detector (AD3818 modules seem easy to come by?). What's I'm unsure of is what to do from there. I've seen some projects labeled "Arduion RF power meters" that just sample the output of the AD3818 directly, but I don't see how that's actually measuring power.
I see that AD also makes true RMS RF power ICs - are those what I need?
MasterT:
Get RTL2832 module from China, plug into laptop and scan a band. The chances to make good RF detector w/o experience close to null.
resistor:
If I just wanted to solve it with money, I'm sure one of those $50 signal analyzers could probably tell me the answer. I'm noodling about how to do it as a learning exercise...
srb1954:
Why not just try using your receiver to see if there is excessive interference?
Tune your receiver to a quiet channel, flick the LED lights on and off and see if there is a noticeable increase in receiver noise level when the lights are on. Repeat the procedure for as many channels as possible.
resistor:
--- Quote from: srb1954 on September 07, 2020, 02:13:17 pm ---Tune your receiver to a quiet channel, flick the LED lights on and off and see if there is a noticeable increase in receiver noise level when the lights are on. Repeat the procedure for as many channels as possible.
--- End quote ---
This definitely works, but is somewhat time consuming. I'd like to be able to quick test different modules. I'd also always be wondering if it might be fine when receiving a strong signal but still cause issues when trying to understand a far away signal, or when transmitting to a far away station.
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