The AM Forum

Alright, this is my recently built antenna tuner for open wire feeder. Its link coupled, very basic, few adjustable components, but I made it semi automatic, meaning that I have an arduino controlling the stepper, turning the vac cap, and also controlling the ruskie relays for coil taps. I have the tuner located away from the shack. In the future it will sit in the garage, separating the antenna even more from the neighbours.
Tuning is done in a "tuning menu" where motor steps and relay activations are stored in eeprom, and gets called whenever that QRG gets called. Turned out nice. Had good help from Mike at SJ2W, who milled the parts from plexiglass,which made it look so neat.
Brake line (CuNi alloy) is used to wind the coil, brass strips are bent into reconfigurable clamps, nema 17 motor, 5-250pf cap, 3 pairs of ruskie relays and end stop switch make up the tuner. I made a separate driver box which i located by the tuner. The driver contains the stepper motor driver, 24v power supply and a relay board. Communication between driver and arduino takes place over 2 ethernet cables. The arduino sits under the top desk in the shack, and is controlled by 2 buttons and 1 encoder. One button changes band, the encoder steps between QRG's. A long press on the other button enters tuning mode, where relays can be stepped through, and motor can be turned using the encoder. A press on the bandswitch button saves the value to an eeprom location associated to that QRG.

Very nice work !   Mounting vacuum variables is always a bit of a mechanical problem, but I like those heavy plexiglas machined supports.  That tuner should handle many kilowatts if necessary.
73 de Norm W1ITT

Very cool.  I have often thought about doing something similar.

My total lack of coding skills keeps getting in the way.

Impressed x 2.


--Shane
KD6VXI

I really like that, especially the limit switch.

Very impressive. The remote function solves the bringing the open-wire into the shack problem.

Tommy,
That is a nicely engineered tuner. Very nice work indeed.  Good job. I like those relays.  Ever thought about making the tuner wireless?

i've been working on a remote tuner on and off for a few months but rather than hardwired it is 2.4GHz wireless using 2 Arduino's in a master/slave configuration where the slave will  be battery powered and kept alive by a small solar panel.  I have the master/slave setup somewhat working and it will work at more than 100ft below grade through my basement wall but like Shane, my coding skills are horrid. Getting it to work  the way I want hasn't been achieved yet but close to usable.  Still pecking at the code to "fine tune".  Haven't built the tuner mechanism yet as I'm still working the Arduino code. And I have no clue how it will behave in an high RF environment.  Would like to build something similar to yours or the JJ Tuna.  Again, nice work.

I havent. Until now :)

I have been experimenting with an I2C bus a few years ago, and I'm confident that implementing that on this system would be no problems at all.
I used "expansionWrite" to make the I2C project work (also a link tuner, but with a servo turning a air variable cap, perhaps it can be be used in an rf link as well.
Here's a reference http://rodelectronics.blogspot.com/2010/03/expand-io-ports-with-another-arduino.html?m=1
Will relocate this antenna in the autumn, and was thinking of setting up a "Barn-slave Arduino" to do antenna switching, turn a rotator, and also to control this tuner. An rf link would mean less wiring..

The arduinos I have used around rf fields have faired well. On this tuner there was horrid relay chatter when loading up on 160 and 80, but that turned out to be due to the total lack of bypass capacitors on the chinesium relay board I was using to pull the large rf relays. Added smd caps to the optocouplers at the board, and issue disappeared. The stepper driver I'm using, also chinesium, doesnt like to work under rf, it does work, but misses steps. Should be possible to decouple it better as well. Servos are very sensitive. I had to use a relay to break the vcc to them before applying rf, or they'll started to act as windsheild wipers.

excellent work !

what is the main coil diameter ?

Peter

Some easy-to-use RF link modules are HC12 ...  look on ebay, less than $4 and they work great. I have used 6 of them with arduinos in telemetry.

It's 2 3/4" (or around 70mm here on the metric side of the lake)

I looked at the HC12 as an option and even bought a few for my project but then I came across some arduino shields based on the RFD21733 module. It works as a wireless RS-232 connection with error handling/correction and plugs right into the Arduino Mega. Just 2 serial commands in the code and you're off and running as if using a pair of wires for the serial connection. A little more expensive but totally idiot proof.