Field Strength Meter

This station accessory is based on the NJQRP Sniffer.

Back to Contents

Field Strength Meter A dual-tuned toroid (stacked T68-6s) is used as the resonant input circuit and tunes 80 through 10 meters. The meter and sensitivity pot are scavenged from an old Radio Shack FS meter that didn't work too good. To provide a greater range capability, the FS meter includes the Accuprobe kit (ApK) as a diode compensated meter amplifier. The schematic below shows how the FS meter circuits are integrated with the ApK. FS Meter Front
FS Meter Inside The controls on the front are tuning, and left to right, Accuprobe power, sensitivity and the selector switch for diode detection only or through the ApK. The inside view shows the components with the dual-tuned toroid mounted directly to the dual poly variable.

The components are installed in an LMB 136P Interlocking box. The 9V battery supplies power to the ApK board when used. The ApK is mounted along the bottom. .

Accuprobe Kit Modified This is the Accuprobe kit modified for use as the diode compensated meter amplifier. The kit was designed and used with permission here by the NJQRP club’s Joe Everhart, N2CX. It is being sold through AmQRP by the NorTex QRP club.

Use of the Accuprobe provided an easily modified circuit for the meter amplifier. The modifications shown in the schematic below provide a circuit similar to the NJQRP Sniffer kit.
FS Meter Amp


Accuprobe Field Strength Meter Schematic

Accuprobe Schematic