Wide Dynamic Range Field Strength Meter

Posted on Feb 5, 2014

A field strength meter is a very handy tool for locating a transmitter. A sensitive field strength meter by itself has some limitations, however: It will respond to practically any RF signal that enters its input. This property has the effect of limiting the effective sensitivity of the field strength meter, as any nearby RF source (or even ones f

Wide Dynamic Range Field Strength Meter
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ar away, if the meter is sensitive enough. ) will effectively mask the desired signal. This property can be mitigated somewhat by preceding the input with a simple tuned RF stage and, in most cases, this is adequate. A simple tuned circuit does have its limitations, however: It is only broadly selective. A simple, single-tuned filter will have a response encompassing several percent (at best) of the operating frequency. This means that a 2 meter filter will respond to nearly any signal within to the 2 meter band. A very narrow filter can be tricky to tune. This isn`t usually too much of a problem as one can peak on the desired signal (if it is close enough to register) or use your own transmitter (on a nearby frequency) to provide a source of signal on which the filter may be tuned. An obvious approach is to use a receiver. While many receivers have "S-meters" on them, very few of them have meters that are truly useful over a very wide dynamic range, most firmly "pegging" even on relatively weak signals. While an adjustable attenuator (such as a step attenuator or offset attenuator) may be used, the range of the radio`s S-meter itself may be so limited that it is difficult to manage the observation of the meter and adjusting the signal level to maintain an "on-scale" reading. Another possibility is to modify an existing receiver and interface it with something like the Wide Dynamic Range Field Strength Meter - and that is...

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