Maximite and the ESMC receiver

I’ve been playing with the Maximite to control the Rohde and Schwartz ESMC receiver I recovered from flood damage (see Silicon Chip Magazine – June 2011). These receivers are pretty much just grey boxes, some versions have a nice digital front panel, mine don’t – it’s all controlled be software via the RS232 port. Here are some of the shots of my efforts…

This is the interface, just a MAX232 on that little board does the level translations to RS232. The cable goes off to the serial port on the ESMC receiver (19200,8,N,1). The ribbon cable at the top comes from the Maximite to a ‘breakout’ board, which is just a strip of veroboard with a single in line pin header installed. Each of the 20 I/O pins are mapped to the connector. Connections (right to left) are GND, PINs 1-20, 3.3V, 5V, GND. I installed the bargraph LEDs and resistor arrays (those black stripes below the LEDs) as an easy way of showing what was happening on the port.

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So far I’ve implemented fixed frequency monitoring (20-650MHz), bandwidth control (500Hz up to 100kHz!), demodulation control (FM, AM, LSB, USB, etc), scanning and a command line control.

This is the shot of the screen with the scanning mode functioning, if the signal breaks through a set level, it’s frequency is recorded on screen. Each printout is cascaded up to ten levels down the screen to reduced clutter. The scale on the left of the screen is not accurate by the way!! The current frequency and signal level are at the bottom of the page. The graphing, spectrum analysis scrolls from the left to the right in a continuous loop.

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