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Testing the NE555P IC audible RF field strength meter from Peter – VK3YE, well known as the Squeakie ( the meter, not Peter ha ). First PCB design made by my friend Stefan – YO5ASB. It can detect a 1W VHF / UHF handheld from about 2 or 5 meters away. As promised in the video, I also designed a PCB board for you to order, or you can make it at home. I had a lot of fun with this simple device and I really enjoy it. I find it really funny that it sounds like a Geiger counter.
THE SCHEMATIC
There is not much to talk about as there are only a few components on the board ( Fig. 1 ). Is a simple NE555P voltage controlled oscillator, connected to a diode and short antenna to detect the presence of RF. I like calling it RF sniffer and it seems pretty sensitive. The 15K resistor and the 10K potentiometer allows you to vary the bias on the diode ( 1N4148 ). This way you will be able to adjust the sensitivity of the RF strength meter.
Fig. 1 – Audible RF Field Strength Meter Schematic
PCB BOARD
I designed the PCB board ( Fig. 2 ) because the design my friend made, was not suitable for the toner transfer method. The PCB board is now easy to make at home by using the toner transfer method. But as you already know by now, I prefer to order them from PCBWay.
Fig. 2 – Audible RF Field Strength Meter PCB Board
PUTING IT TOGETHER
The one made using the PCB boards I ordered ( Fig. 3 ) turned out perfectly. Now all I needed was a speaker, a telescopic antenna and an enclosure. Just a tip, is good that you use a larger speaker as it’s easier to hear it from a longer distance. Of course that into the enclosure it will sound even louder ( depending on the enclosure ). I am powering it from a simple 9V battery.
Fig. 3 – Audible RF Field Strength Meter
I had a nice enclosure from my friend Andrei – YO6TJ, so I put it to good use. It turned out really well ( Fig. 4 ) and it seems that one battery can last for months. I intended to make it even smaller, but instead I used the enclosure I had available, so it turned out a little bigger. It looks great though and it’s really loud too. I may build a smaller one in the future easy o pack.
Fig. 4 – The Finished RF Field Strength Meter
OPINIONS ON THE SQUEAKIE
There is not much to say about this audible RF field strength meter. Is fun having this tool, and the Squeakie name I like the most. I am playing with it at the moment testing the radiation pattern of my antennas. Is may be just a simple tool, but at the same time is very useful too.
I know that I may build other field strength meters, possibly the more traditional ones that are very sensitive and a little more precise. But I still think the Squeakie will be useful to me as well. All I have to do now is to find a nice enclosure and put the circuit and the speaker inside. I think it makes a good present for kids in a radio club as a project they could build in less than an hour I am sure. I hope you enjoy it as much as I did.
73, YO6DXE
