Schematics > RF circuit > Sensitive Field Strength Meter
Sensitive Field Strength MeterDescription:
This Field Strength Meter is simple and also quite sensitive. It uses an
ordinary digital voltmeter to measure RF signal strength up to a few hundred
MHz.
Sensitive Field Strength Meter circuit
Parts List:
1 OA91 Germanium Diode
1 3.3M Resistor
1 100p Capacitor
L1 7 turns on a 1/4 inch former (suitable for around 100MHz)
Notes:
The multimeter should be set to the lowest dc volts range for maximum
sensitivity. This is normally 200mV DC for most meters. The circuit works well
at VHF (around 100MHz) and was quite pleased with the results. L1 was 7 turns on
a quarter inch former with ferrite slug. This covered the UK FM band. A digital
multimeter, as opposed to an analogue signal meter offers several advantages in
this circuit. First, the impedance of a digital meter is very high, around
10Meg/Volt on most meters. This does not shunt the tank circuit unduly. Second,
compared to an analogue meter, very slight differences in signal strength can be
more easily observed. Thirdly,a digital meter will have better linearity,
responding well to both weak and stronger signals.
Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk
Title: Sensitive Field Strength Meter
Source: unknown
Published on: 2006-01-15
Reads: 441
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