View from the Front

Frequency Range	0.099 ... 29.999 MHz
Level Range	-99.9 ... -9.9 dBm, 7 dBµV ... 97 dBµV
Power Supply	12 ... 15 V, 499 mA
Remote Control	yes
Measurement Bandwidth	see below. Approx. 5 kHz

The mastermind of this design is of course the Arduino Nano Every. It displays the status on the 128 x 64 px oled display. The Arduino Nano also handles the Serial Communication (Can be USB or Envico).

The Design uses the "classical" double-super concept. A very high first IF is based on a SAW Dect Filter, running at 110.592 MHz with a Bandwidth of 1.728 MHz. (Epcos, B8104). A Mixer (NE/SA 612) powered by a 100 MHz XCO takes over and feeds a 10.7 MHz crystal filter, made out of 4 crystals. Hand-selected, of course.

The RSSI is is measured by an AD8307 in collaboration with an AD603. This circuit follows the recommendations in the datasheet. Instead of using the 10 mV/dB tap, replica builder should connect the output (Pin 4 of the AD8307) directly to the ADC. This will improve the resolution by approx. 1 Bit.



View inside. Classical superheterodyne approach.

The crystal filter is split into two blocks of four crystals. It is our standard design, found elsewhere on this website. The two blocks are separated (isolated) by a buffer amplifier (BUF 602, High-Speed, Closed-Loop Buffer from TI).

The 10.7 MHz Intermediate Frequency is also made available at the rearpanel (BNC) for demodulation e.a.

We used SQCB low ESR Capacitors from AVX RF (Sample Kit). Using 'any' capacitor may ruin your day (and the filter frequency response).

Using the Ningmod with this script, we swept at a Center of F = 9 MHz, Span = 40 kHz, with a Power of P = -20 dBm and N = 100 Points to measure the IF Filter Response. It looked liked this :

Remote Control with e.g. HTerm 0.8.5 from Tobias Hammer

Antistatic Foam greatly reduces crosstalk from the Arduino ...

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