NDB CAS

Back to an old passion: VLF NDB hunting. But this time, "live".

Right next to a swimming pool I noticed a weird tower with a capacitance hat and typical white and red stripes. Landing airplanes to Torino Caselle (LIMF) airport passing just over it. Online resources and maps locate the CAS NDB right there.


A detail of the capacitance hat. Don't ask me their length.


A more poetic view of the instllation.

FT817 CAT interface, a clarification on the wipeout warning

So far I have noticed very little interest in my keypad. I hope it is not because of the explicit warning about possible radio settings wipeout, but let me clarify things.

The keypad does not send potentially dangerous data. It sends and reads data as ANY OTHER computer software does. The fact that the keypad uses FT817 "proprietary" commands/extensions does not increase the risk of losing soft calibration settings.

Data (or, more generally, "information") may corrupted on the transmission path by external causes and thus be improperly received. This may happen both with my keypad and any other CAT control software.

Since I do not use CAT control programs I do not know if their documentation issues an accurate warning of total wipeout risks.

I prefer to tell the whole story and provide a preventive measure to recover from such an accident.

So, why hesitate?!

Surplus source for CAT cable

Since soldering MiniDin8 connectors is a tough job, I have found out that in the past there were two commercial applications using these cables:

• Sun SPARC and 3/80 keyboards
• Apple Macintosh RS-422
  

According to a websearch ("sun keyboard pinout"), the Sun keyboard cable has two couples of shorted pins. Fortunately they are not vital for the FT817 keypad application: just eradicate them (pick the right ones!). I've done it and it works.

The same website shows a more friendly pinout for the RS-422 cable, that would be ready to use right away.

One problem: how to find these cables?

FT817 keypad - a suggested assembly

This is the first (and last) keypad I made not for personal use. It is on a veroboard/perfboard and takes about 5x5 cm. I have used a 4 way connector for the cable towards the ACC port and 8-way pin headers for the keypad. I prefer this latter solution to my development board that uses 8 independent wires.


This way the keypad sits on top of the circuit, effectively reducing the overall footprint to a bit more than the keypad itself.

For the reset button I installed only two pin headers, if the owner-to-be will feel the need to add one. The LED is wired permanently to the board.

The cable is 1m long, and did not show any communication error during workbench tests.

These pictures are provided as a guideline for you, homebrewers out there.

Please note that I am not available for building a keypad for anyone for less than 100 Euro, shipping included, advance payment. I hope this amount is high enough to encourage you into homebuilding this keypad. If you have troubles locating some parts, see the keypad homepage for some directions.