RFzero Signal Generator

Last edited: 8.12.2023
Here my solution to the RFzero Signal Generator:

I decided for the graphical TFT display, two encoders (for frequency and attenuation) and a keypad.
I used a housing I had in stock, it is a little small so I had to shrink everything.
So I had to remove all SMA connectors and connect by soldering shielded wire directly to the PCBs.

The components in my generator are:
Display: 2.8″ TFT SPI 240×320 (eBay)
Supply: 8-20V DC (13V 0.06A) with step down converter to 5V (eBay)
Encoder: top is for frequency, bottom is for attenuation
Expander: SX1509 (eBay)
Attenuator: RFzero I2C in mode 7 (11 bits, 0-106,5 dB in 0,5 dB steps). Please note, this is a RFzero prototype and will not be available for sale because of bad performance at high attenuation. We have a 76 dB version in progress, maybe that will be available at a later time.
Case: I used a aluminium box. It is 200 mm wide, 70 mm high and 130 mm deep.

Front view (no GPS antenna)
Top view with short form command overview
Top view
View on back side of front panel, display and keypad mounted with hot glue
Display and LEDs, with GPS antenna connected

Green – Power ON
Red – Output on
Blue – GPS impulse
Yellow – GPS Ready

Here a shortform of the command syntax, very hard for me to remember :-).

Here the schematic in pdf of the external connections to the display, attenuator, SX1509, encoders, keys and keypad: SigGen_oz2xh_200924


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