Start your measurements by using low transmitter power and a near minimum sensitivity on the field strength meter.
Rf field strength meter circuit diagram.
This rf field strength meter has no absolute scale if we don t calibrate the scale using a standard instrument but the important thing for this.
The circuit use only one transistor mpsa18 as the active component.
The main stage acts as a crystal recipient.
For operating with 9 volts simply remove d5 and d6 diodes.
Field strength meter this portable 90 db dynamic range rf field strength meter is simple to build.
It is important to use all leds from a same manufacturer same color and type because there is some difference between brightness and other.
The circuit is using four leds which will show the low medium high and full signal strength indications.
This rf field strength meter has no absolute scale if we don t calibrate the scale using a standard instrument but the important thing for this uncalibrated rf meter is that it can display the changes of an rf field when we calibrate the antenna or.
There is not much difference between the two circuits but only the 2n3906 pnp transistor used at the output of the figure 2 circuit to further increase the sensitivity.
Utilize a germanium locator diode like 1n34 yet aa119 is substantially more normal in europe a silicon one won t do.
It can be used from 2 meters to 160 meters.
Adjust c1 for peak reading.
The operating voltage of the circuit is 12 volt dc but you can also operate the circuit with 9 volts.
The frequency is controlled by l and c.
The variable resistor on the field strength meter figure 3 the case circuit board and antennas for the field.
The signal strength meter display uses analog meter 1 ma full scale.
How the circuit works.
The circuit is built around a ca3140 ic which is an operational amplifier.
7056 railway ave courtenay bc v9j 1n4 canada.
The signal strength meter display uses analog meter 1 ma full scale.
You re measuring field strength from a transmitting vhf antenna use a vhf an tenna on the field strength meter.
Considering these factors a dual mosfet is used as an rf amplifier in this circuit.
L1 480 khz to 2 4 mhz l2 2 4 mhz to 12 mhz l3 12 mhz to 40 mhz the antenna is made of 30 cm long metal rod.
This is an exceptionally simple rf field strength meter circuit.
Field strength meter circuit diagram.
The field strength meter or rf detector circuit shown in figure 1 is a simple circuit using not more then 8 parts and a battery.
To use turn on transmitter and meter.
This circuit is a simple field strength meter that chooses a specific frequency range.
The telescoping antenna may be adjusted to its shortest length when working at 2 meters to keep the needle on the scale.
The amplification can be adjusted by p1 and with s1 switch we can select three frequency ranges.
This circuit is another radio frequency rf field strength meter similar with our previous field strength meter circuit but with lower supply voltage only a single cell 1 5v battery.
Also be used as wide band rf detector.
The circuit use only one transistor mpsa18 as the active component.
