ThisRF Wave Absorbion meterwill detect signals between 10cms and 10m away all acording to the setting of the 22MegOhm gain adjustment potentialometer and the power of the transmitter. The RF signal is detected across the germamium OA91 doides and rectified to a d.c. level driving a 10LED driver IC. The LED’s are marked 1 to 10 indicating the strength of the detected RF signal. This circuit is ideal for tuning up low power transmitters or locating hidden transmitters. If a specific frequency band is required, replace the OA91 diode that goes to negative with a parrallel tuned circuit as indicated. For 27MHz L=10Turns and C=39PF, for 50MHz L=7turns and C=27pF, for 80MHz L=5turns and C=12pF, for 110MHz L=4turns and C=10pF, for 150MHz L=3turns and C=8.2pF and for 180MHz L=2Turns and C=2.2pF. All coils are 22SWG wound on a 10mm air former.