VE2TZT
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Re:low band antennas keyboard - 2011/01/31 21:06
FUNCTIONNALITIES
To test this whole process while learning it, I decided to build the first stone of my low band antenna system project that is the direction and switching control keyboard. The idea is to have one the same keyboard 4 sets of 8 keys controlling the 8 directions of 4 antennas and one set of push on/off keys for controlling the switching or various mixing, swapping and diagnostic functions. Using a PIC in that project will permit to modify ‘’in the minute’’ the functionalities when needed, the imagination being the only limit.
Each key has it’s led lighted if pushed or selected.
The outputs of the keyboard will permit different choices to control the future antenna system : 20 binary open collector sink outputs plus one TX/RX serial output with separate RS232 (for a computer connection) and RS422-485 plugs.
The 20 binary output are for 3bits X 4 antennas (3bits=8 directions)+8 push-button output.
The RS422 is a symmetric electrical protocol which permits 1000 feet twisted pair (Cat5) serial transmissions on a multipoint bus in noisy environments. The idea is to dialog with the antenna controllers located at the feet of the antennas with only one twisted pair of CAT 5 wire. The advantage is lower command wire cost, possibility of distant diagnostic and of course, more plasticity in the antenna pattern.
REALISATION
I have designed and realised everything including the metal box, I have sent to Victor some pictures that are speaking by themselves, I thing that he will put them soon on this site.
Just two point:
-I have designed and realised two double sided PCB, one for the keys and the leds and one for the processor and the i/O
- Half of the array of the processor board is for protections: shorts of outputs, reverse voltage of power input and of course RF protection: each output including serial one has its choc coil and capacitor, even the 12V power inputs (plus and minus), and all the common (ground) outputs have they 1mH choc: I will not want the common mode to travel from one antenna controller to the other and by the way to the antenna radials etc...We are on 160m. This way, the PCB ground is connected to the metal box at only one point and the metal box itself is connected to the station ground at only one point everything else is as RF isolated as possible.
Gilles VA2EW VE2TZT
Post edited by: ve2tzt, at: 2011/01/31 21:19
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