Pic Based Power Meter from the ARRL Handbook

This is my version of the " KA7EXM PIC based mW Power Meter " as featured in the ARRL Amateur Radio Handbook 2007, I decided to build it as part of the collection of test gear for my Amateur Radio station so that I could test my Table Top 200 Watt 145MHz Amplifier ( and other future projects ) the boards were drawn up to incorporate long reach push button switches rather than the seperate switches of the original design so that a single module for the PIC and LCD display could be fitted to the front panel of the instrument with just four screws .The RF head was designed to fit in a standard tinplate box available from a couple of UK suppliers. I also changed the 78L05's in the original design for equivalent LDO regulators to enable me to use a " NiCd / NiMH " rechargeable battery which is normally 8.4 volts, the software being latest version ( V2.0.0 ) downloaded from the KA7EXM .net website ,.Having built & tested the unit , I've decided to investigate the possibilites of using other similar power detectors available to make a similar unit for VHF / UHF upto 2.5 GHz to cover the 2m ,70cm, 23 cm and 13cm / 2.4 GHz bands. The new Power Meter RF head will use the " Hittite " HMC713MS8 log amp / detector IC which although it has a reduced dynamic range compared to the AD8307 of the original design , but a broader frequency response together with a nearly flat sensitivity mV / dB across the frequency range 100MHz - 2.5 GHz of about 17mV , the addition of a small attenuator ( of approx 10dB) whilst decreasing the sensitivity has the advantage of improving the return loss ( VSWR ) and protecting the RF detector from accidental overload .The calibration of the unit following the procedures in the ARRL handbook as per the original .

Picture of the Completed Power Meter

picture of the completed Power Meter

Circuit diagram of the Power Meter

Circuit of Power Meter

Top Silk layer

Top Silk layer

Top Copper layer

PIC Power Meter Top Copper

Top Copper layer( Mirrored )

PIC Power MeterTop Copper ( Mirrored 0

Bottom Copper layer

Bottom Copper layer ( Artwork )

CAD drawings of the Front panel

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This page last updated 21st Oct 2009