M3 FPM-1 Kit Tips

Frequency Counter Sensitivity (V/UHF)

We were made aware of a possible problem with the FPM-1 Frequency Counter sensitivity in the V/UHF (CH2) mode. We were able to isolate the problem to some marginal SD101A schottky diodes we received. These diodes (D3 and D4) are used to clamp the input on CH2. If your counter displays low sensitivity at frequencies between 100 MHz and 1 GHz, we recommend replacing the two SD101A diodes with 1N4149 diodes. Replacement diodes are available to the original purchaser, free of charge, from M Cubed Electronix, Inc.    Email our tech support at the address on our Contact Page for more information.

Sensitivity can be further improved by placing a ferrite bead on both leads of the two 1N4149 diodes (D3 and D4). A -61 or -64 mix is recommended. All kits now ship with 1N4149 diodes in place of the SD101 diodes. Ferrite beads are not provided with the kit.

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