Custom Products from Masters Communications

Brief Description:
Nothing beats having a real communications Service Monitor to test FM radios and repeaters for various functions, but they are incredibly expensive new, and even used ones (that are worth while) are commonly $2000.00 or more. This project is based on a Raspberry Pi Pico2 and with software written by a Andy - K3JSE, a complete FM deviation meter with excellent accuracy results. The test equipment offered here is an attempt to provide a better solution than anything prior, with reasonable accuracy, on a hobbyists limited budget.

The K3JSE Deviation Meter provides direct / accurate measurement of Frequency Modulation from 0 to over 5kHz deviation with modulating frequencies from 50 Hz to over 4 kHz without the need of a computer, SDR, or spectrum analyzer or involving Bessel nulls or any complicated math. The system is comprised of a receiver, digital measurement unit (DMU) and optional OLED display with 3D printed case. These components are available individually, and most in kit form or the entire system assembled, tested and calibrated.

A modified police scanner is used as the receiver. It is a current production Uniden "Bearcat" BC355N "police"scanner (chassis 367E) that is modified by adding a 3.5mm (1/8") stereo jack to its rear panel to bring out discriminator audio and squelch logic signals. These signals are routed through a stereo audio cable (included) to the Digital Measurement Unit where the discriminator audio and squelch logic is processed. The board shown above is the heart of the system and is powered by a source of 5VDC through the USB jack. Power for the DMU can come from a USB power supply, USB charger or computer with a USB A connector. A USB A to USB B (printer) cable is provided with the purchase of the DMU.

If connected to a computer - several advanced functions are provided, as well as meter faces that can be used in place of the OLED display - allowing the DMU to do everything and all data is displayed on a computer running software that is available free.

There is one RJ45 accessory port for connection of the optional DMU OLED display and 4-position function switch bank. A short Ethernet cable is used for connecting the display and switch bank to the digital measurement unit. A short Ethernet cable is provided with the purchase of the OLED display in a 3D printed case.

FM deviation in the form of analog voice, digital voice or data, CTCSS / CDCSS tones, DTMF tones, VARA FM [QAM] (wide or narrow) and 1200 / 9600 baud packet can be accurately measured - to name a few.

What's Required:
The Uniden BC335N scanner is a programmable / frequency agile receiver covering several commercial and amateur HF / VHF / UHF bands. Deviation and Frequency Error (offset) measurements are built off of this receiver platform, and it is a required component. The scanner is available already modified for directly connecting the Digital Measurement Unit (DMU). All of the components of the deviation measurement system are available separately, but, a modified scanner, digital measurement unit, and the OLED display is required to make self contained deviation measurements. Except for the scanner, everything is available in kit form or assembled/tested and calibrated. There are no cables to build - the components connect together with pre-made cables that are included with the purchase of the corresponding product.

Simple Operation:
To measure deviation, connect the system together with the supplied cables, apply power to the scanner and DMU, set the frequency into the scanner, and read the deviation on the display.
Optionally, store the frequency into one of the 300 memory channels to be later recalled (or scanned).

Please navigate to and read the detailed description page below - when you have time.
Detailed Description of the K3JSE FM Digital Measurement Unit.

Features:

	Small size - - does not require a computer or expensive / difficult software.
	Simple to hook up and use. Takes the guess work out of setting transmit audio levels.
	Measures and displays deviation directly - in both an OLED display and analog meter faces on a computer screen.
	Frequency Coverage of the BC355N Scanner: VHF Low Band = 25.0000 - 54.0000 MHz 28 - 54 MHz FM Aircraft Band = 108.0000 - 136.9916 MHz (AM) VHF High Band = 137.0000 - 174.0000 MHz UHF Band = 406.0000 - 512.0000 MHz 800 MHz Band = 806.0000 - 823.9875 | 849.0125 - 868.9875 900 MHz Band = 894.0125 - 956.0000 MHz
	Accurately measures all Two-Way FM modulation forms from 0 to over 5 kHz deviation from DC to 3kHz of modulating frequency within 4% accuracy. The frequency response extends from 30Hz to beyond 5400Hz at 10% or better accuracy.
	Deviation is read directly on the OLED display and is accurate within 4% for modulating frequencies of 3kHz and under - immediately upon power up.
	Frequncy Error is shown on the OLED display (Ferr) and is accurate within 200 Hz or better after a 10 minute warm-up of scanner.
	The DMU has onboard voltage regulation for all critical signal processing, measurement, and logic circuitry.
	An affordable alternative to a service monitor - providing very reasonable accuracy. Assembled-Tested-Calibrated units are calibrated using equipment with NIST Tracable Calibration.
	Cables to connect the components together are included in the purchase.
	DC Power Cables (pigtails) are supplied with the Uniden Scanner. (When purchased already modified from us) and also the Analog Measurement Unit (AMU).
	The OLED meter display 'panel' does not require a power source. The digital (LED) bar-graph display (DMD) gets its power from the AMU.
	A perfect companion to the popular FM RF signal generators (marketed as walkie-talkie testers) available on eBay and other outlets. Gives you the capability of many of the tests provided by a real Service Monitor at a fraction of the cost.
	90 day Limited Warranty.  Repair and Recalibration available for units out of, or not covered under warranty (my determination).
	Calibration of the units should last for years of normal storage and service. TBD.

 

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