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Spy Circuits
EXPERIMENTING
Take the Voyager project and connect 30cm of tinned copper wire to the antenna point on the PC board. Holc Meter in your hand (keep away from the actual Circuit by holding the multimeter) and bring the receiving anter Voyager antenna, without touching it. As you move up and down the Voyager antenna, watch the needle. it will show that energy is not radiated uniformly from the antenna but has a maximum and minimum value. It where these occur. Measure the length of the antenna and plot the results. Cut 2cm off the antenna and repe 175cm antenna to the bug and repeat the tests.
This will give you a good understanding of the phenomenon of electromagnetic radiation.
There are lots of other things you can test with this project.
The Field Strength Meter Mkll is presented in the next article and has the advantage of a tuned front end and This will enable you to not only peak transmitters but also find the frequency on which they are operating.
It detects in the rangę 75MHz to 140MHz enabling you to design and build transmitters capable of transmittin: broadcast band.
But don't put off building this project as you will need both of them as they have different capabilities. And yoi Power Meter.
Test eguipment is very important when working with RF so don't put it off any longer, start now and build up y
FIELD STRENGTH METER Mk II
A Field Strength Meter is essential when designing and building transmitters. It provides signal strength value compare and estimate the efficiency of a transmitter and its expected rangę.
SUMMARY
• Checks the output of low-power
transmitters
• 3 LED readout
• Detects from 75MHz to 140MHz
Notę: the pointer is not soldered to the trimmer correctiy. When the plates are fully disengaged, the pointę
75MHz.
Notę: The bottom 3v lithium celi should be insulated from the holding wires so that the cells do not "short-c
around the bottom of each wire.
Field Strength Meter Mk II
2011-12-08
mk:@MSITStore:F:\spy circuits.chm::/SpyCircuits-l.html
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