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41 — Our new ARDF 80 m transmitter will soon be used.

2015-10-11. By Patrick.

Fig. 1.    Top view of the transmitter outside its box. Each part was created as a separate module. Our OSH Park ATmega328 breakout is soldered onto the module at the upper-left. At the lower left, the Adafruit Si5351 can be seen. Just to the right of it, the driver module was the first one that had to be totally replaced during development.

We finally got the 80 m transmitter working enough an event coming up this Saturday (10-10). Actually, the event will already be done by the time this is posted. I hope it went well.

The outing is being organized by Kelly and some of the teachers at Smith Middle School. It's an "Avatar Club" outing, about 12 school kids that will be divided up into two groups. One will do a nature/geology hike and the other one will do an ARDF event. Then the two groups will be swapped.

So this is the first test of our equipment in more than a practice for us. We'll be using the two transmitters we built earlier as foxes. That is, they will be the hidden ones the kids will have to find. The newest transmitter using the Si5351 as an oscillator will be used as a homing beacon and for demonstration purposes. It's never been used even for a practice.

So how far did we get in the building? Well, it's kind-of working. There is still some problem with getting power out. I think I need to re-design the driver, again. Still though, it's putting out about as much power as our other two transmitters. So that's cool. Also, it's transmitting on a different frequency! And that's very cool. The code is only partially complete. The timing works well. A couple missing features are the ability to shut off the Si5351 and the ability to change the frequency from the front panel. But these these two are just software changes. And I have a couple ideas to try for the getting more power out.

So overall, we didn't quite get the project completed before the Avatar Club outing but enough to feel a great sense of accomplishment. I can't wait to get it out there and actually use it for the first time.

Fig. 2.    Side view of the transmitter. The battery pack is at left on lower level.

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