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Field Strength Monitor / Meters
 

Last Updated: November 30, 2017 07:44 AM


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

A Field Strength Indicator-Analog only -  The circuit is powered by a single 1.5 volt AA cell.  The current drain is so small, about 60 microamps, I didn't bother with an on-off switch -I just slip a battery in for the day, and hope I remember to remove it when I'm done.  The supply voltage can be increased up to the breakdown voltage of the transistors to increase the sensitivity, but bewarethe sensitivty to thermal drift will increase as well.   __ Designed by Dick Cappels

A Wide Dynamic Range Field Strength Meter -  This unit is an updated version of the Wide Dynamic Range Field Strength Meter.  While the basic function is the same, it has several critical differences: It uses a specialized integrated circuit, the Analog Devices AD8307.  This chip is designed specifically as a logarithmic amplifier for use through 500 MHz__

Field Strength Indicator-Analog only -  The circuit is powerd by a single 1.5 volt AA cell.  The current drain is so small, about 60 microamps, I didn't bother with an on-off switch -I just slip a battery in for the day, and hope I remember to remove it when I'm done.  The supply voltage can be increased up to the breakdown voltage of the transistors to increase the sensitivity, but bewarethe sensitivty to thermal drift will increase as well.   __ Designed by Dick Cappels

Field Strength Meter -  The circuit draws less than 10 uA with no signal so no switch is required.  The variable capacitor is adjusted to tune the meter to the desired frequency by adjusting for the highest meter reading when held near the transmitter's antenna.  If the meter reaches full scale during tuning or use, move the meter further from the antenna.  (As you peak up a transmitter, you may need to move the meter several times to keep it on scale.) The MPSA18 may be replaced by other high gain NPN transistors, if desired. __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Field Strength Meter -  This is a wide band signal strength meter circuit which responds to small changes in RF energy, designed to be used for the VHF spectrum and will respond to AM or FM modulation or just a plain carrier wave.   __ Designed by Andy Collison

Field Strength Meter for 2.4 Ghz Wireless LAN -  The original diode in the Microwave detector has been hard to find.  I have found a supplier for the diodes.  Purchased here: http://www.  xs4all.  nl/~barendh/Cateng/Cateng_diode.  htm Site Main Page : __ Designed by John Samnin

Field strength meter for the 137 kHz band -  The original diode in the Microwave detector has been hard to find.  I have found a supplier for the diodes.  Purchased here: http://www.  xs4all.  nl/~barendh/Cateng/Cateng_diode.  htm Site Main Page : __

Field Strength Meter MkI -  This Field Strength Meter has been specially designed for our FM bugs.  It is capable of detecting very low power transmitters and will assist enormously in peaking many of our FM transmitters that have a coil in the output stage that can be adjusted for optimum output __ Contact: Collin Mitchell

Field Strength Meter MkII -  A Field Strength Meter is essential when designing and building transmitters. It provides signal strength values and allows us to compare and estimate the efficiency of a transmitter and its expected range. __ Designed by Collin Mitchell

Field-strength meter -  I saw this circuit in an old issue of "73 Radio Electronics".  I built it, but it didn't work well, so I changed a few components to get better sensitivity___ 73 Radio Electronics

Field-strength meter -  This is a very straightforward circuit.  The first stage acts as a crystal receiver.  Use a germanium detector diode (like 1N34, but AA119 is much more common in Europe), a silicon one won't do.  The frequency is determined by L and C.  For the FM band and VHF, wind a coil 5mm in diameter, 6-8 turns of coated wire 1mm thick.  You can always vary the frequency by spacing the turns a bit looser or tighter.  C is much less critical.  Something around 100p is preferable, though. __ Contact: IQ Technologies

FSM Field Strength Meter -  This is a wide band signal strength meter circuit which responds to small changes in RF energy, designed to be used for the VHF spectrum and will respond to AM or FM modulation or just a plain carrier wave.   __ Designed by Andy Collison

RF Field Strength Meter -  Most transmitter has several variable capacitors which are used to match impedance for transistors and antennas.  I know people hate trimmers and so did I.  The reason is that it is difficult to trim a system if you can't measure the performances.  To trim a transmitter you need to measure the output power.  Most transmitter are tuned with a dummy load of 50 ohm to substitute an antenna of 50 ohm.  Not everyone has a power meter, and how can you know that the antenna you connect is purely 50 ohm.  If not, the hole trimming is waste of time! What you would like to do is to measure the radiated power out from the antenna you actually are going to use.  If you can measure the radiated energy field you can easy tune the system for max output field strength (max power).  So, how can we measure the radiated energy field? The block diagram at right show you one easy way to measure the RF filed strength.  To the left you find a dipole antenna.  The antenna should be cut to match the receiving frequency__

RF field strength meter -  Most transmitter has several variable capacitors which are used to match impedance for transistors and antennas.  I know people hate trimmers and so did I.  The reason is that it is difficult to trim a system if you can't measure the performances.   __ Contact: maxit91 @ hotmail.com

RF field strength meter Mk1 -  This Field Strength Meter has been specially designed for our FM bugs.  It is capable of detecting very low power transmitters and will assist enormously in peaking many of our FM transmitters that have a coil in the output stage that can be adjusted for optimum output (__ Designed by Collin Mitchell

RF field strength meter Mk2 75MHz to 140MHz -  A Field Strength Meter is essential when designing and building transmitters. It provides signal strength values and allows us to compare and estimate the efficiency of a transmitter and its expected range. __  Designed by Collin Mitchell

RF Field Strength Meter with Attenuator up to 200 MHz -  RF Field Strength Meter with Attenuator up to 200 MHz The RF field meter unit is a great help to tune transmitters for best performance and output power.  You can measure the radiated energy field and can easy tune the system for max output field strength maximum power.  This field strength meter comes with selectable attenuator.  You can use it for measuring the antenna gain and pattern, compare different magnetic field strengths.  See the following RF field strength meter schematic. __

Simple Circuit Field Strength Meter -  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.   __ Designed by Andy Collison

Wide dynamic range Field Strength Meter mark I -  When direction-finding in close quarters, fancier direction-finding gear (if you have it) can become useless due to very strong reflections.   In addition, it may be large, cumbersome, and very conspicuous.   At this point one is often very close to the transmitter itself and it's just a matter of figuring out exactly which tree the transmitter is hidden in or which car has the radio with the stuck microphone. __ Designed by Clint Turner, KA7OEI

Wide dynamic range Field Strength Meter mark II -  When direction-finding in close quarters, fancier direction-finding gear (if you have it) can become useless due to very strong reflections.   In addition, it may be large, cumbersome, and very conspicuous.   At this point one is often very close to the transmitter itself and it's just a matter of figuring out exactly which tree the transmitter is hidden in or which car has the radio with the stuck microphone. __ Designed by Clint Turner, KA7OEI

Wideband RF Field Strength Meter -  Field strength meter is extremely useful when working with RF devices.  It can be used to quickly diagnose whether a transmitter circuit is working, and can be used to detect RF signals in the environment.  The simplest field strength meter could be built with a tuned LC circuit and a germanium diode, just like the way of a building a crystal radio except replacing the ear piece with a high sensitivity current meter.  While this approach fits the needs of most simple applications, it has a pretty narrow frequency range (~100 MHz) and requires tuning the LC circuit to the correct frequency before measurements can be made and the design can become complicated if wider frequency range tuning is desired. __


Field Strength Monitor / Meters


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