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FMDM-150M Deviation Meter
Product Support Documentation

Analog Meter Display (AMD) Board
For Analog & Digital Two-Way Radio Applications


Top side of FMDM-150M Analog Meter Display (AMD) circuit board - shown slightly enlarged.
(Click photo to show a larger image)


(Click photo to show a larger image)

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(Click photo to show a larger image)

Schematic Image - Click to download a high quality PDF.


Overview of FMDM-150M Analog Meter Display (AMD)
The Analog Meter Display "panel" (AMD) is a rather simple type of display, constructed to be practical, accurate, and inexpensive. While not inherently rugged, it's not terribly fragile either. The panel includes two analog meters - one for reading deviation and one for reading frequency error. Both meters are 50uA meter movements that have a 0 - 50 numbering scheme. The reading is taken directly and divided by 10. A full scale reading of 50 is therefore 5.0 kHz on either meter. The deviation meter is pretty self explanitory, and the frequency error meter is handy where netting a crystal or reference oscillator 'on frequency' is necessry. It is invaluable with crystal controlled radios. Also - the error meter allows you to check the calibration of the AMU by simply stepping the input frequency 5kHz above and below the programmed frequency of the scanner and seeing the frequency error meter read +/- 5kHz - each side of zero.

The circuit board for the analog meter display panel has a rear mounted BNC female connector to take the DC coupled signal to an optional oscilloscope (not included). We have tested several of the the inexpensive portable (DSO) oscilloscope kits with a plastic or pre-cut acrylic case found on eBay and AliExpress - and they work fine for this application. Unfortunately many portable scope units require 9VDC to operate, and that supply voltage is not available from any of the deviation meter components. Some portable oscilloscopes are supplied with their own power supply. A portable oscilloscope option isn't currently available from Masters Commumications. We do, however, have a short male to male BNC cable for connecting your own o'scope. Portable oscilloscopes are available from several sources like those already mentioned, or even on Amazon.

The AMD's operation is pretty simple:
 The meters display deviation and frequency error directly, and the BNC oscilloscope output can connect to an optional digital or analog oscilloscope (not included).

Parts List:
If you purchased our kit, refer to the parts list and make sure you have all of the components you need to build it.
Click here for Parts List.

Construction/Assembly:
Click here for assembly instructions and construction notes - with large photo.

Installation:
This device is intended to be installed beside the AMU and connected with a short male to male Mini-DIN-6 cable (supplied).

Calibration:
There is no calibration other than mechanical zero of the two needle meters.

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Product of Masters Communications, all rights reserved.
Specifications may change without notice.
Images property of Kevin Custer - W3KKC
Board layout by Kevin Custer - W3KKC.
HTML December 7, 2025, W3KKC All Rights Reserved!