Raspberry Pi RF Hat UPDATE

You would think that I would not make such simple mistakes when laying out a board. But yeah I put the RF in to the filter to the top of the divider, not into the middle of it where it belongs. Anyway, not a total disaster, cut a track and solder in a bodge wire and its fixed until its broken.

Figured while I am at it, to update the schematic and gerber files and put them all up here for anyone interested in building their own, now that I know things are right and should work without much thinking. The filter is a double tuned circuit, the design software for this type of bandpass filter can be found in EMRFD and I have it for download here on my blog.

GERBER FILES: raspberry_pi_rf_hat_gerber


Remote Control Antenna Tuner

This has now opened up some possibilities. A complete remote control home brew station perhaps? I think it can be done. I think I can even stream audio over wifi quite easily with a MEMS mic and an I2S sound card on the other end and an audio streaming library, then feeding the audio into an SSB transmitter. More to come, but next up will be to expand my 2 button interface into something more resembling a bunch of buttons on a 1990’s looking website HAHAHA. I think i will have to learn some QT programming or Python or Ruby and make a nice looking interface.


Antenna Tuner Details and Files

Ok first off, there is no full schematic for this board, I have already moved on to adding new stuff to it and changing how some parts of it work so I can add in new features. So the best i can offer is this extract that shows where the pins on the micro go to.

Secondly, I wont be releasing my code, the reason is that I do not program using the Arduino IDE and teaching everyone how to program in GCC, to install all the tools required, and uploading the code using an external programmer is beyond my ability to teach anyone let alone everyone. There are just to many things that can and will go wrong and it will only make my life miserable trying to help everyone.

That said, the ESP32 can be programmed in Arduino and the actual basic code is not that hard to write yourself. Turn a encoder and it steps through the relay combinations.

With these relays, I would not put much more than 50w though them. Though the data sheet says they will take 1A but that makes them marginal at 100w. As it stands I think 50w is a very safe bet.

Relays: Omron G5V-1 5V subminiture.
Transistors: PDTC114ET pre-biased SOT23
Caps: 1206 or 1210 Ceramic Multi-layer 1Kv or higher rated, for tuner, 50V 100nF for bypassing. 1uF across the coils of the relays.
Voltage Regulators: 5V and 3.3V 1117 variants SOT223 package.
Toriods: T68-2 T50 would be suitable also, its just what I had, 2,4,8,12,20, 24 and lots of turns.

Schematic as best as i can show without causing confusion because of changes i have made to it. Yeah sorry about that.

Top side of the board as 3d rendered.

Bottom side of the board, 3d rendered.

The board as built by me.

DOWNLOAD: auto antenna tuner_gerber