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Discussion related to construction of Radio Direction Finding gear
This fox is built from a 433 MHz transmitter module commonly available online, driven by an ATtiny85 microcontroller. A 78L05 provides controller power so that the transmitter can run at the full battery voltage. This generates 23 milliwatts on 433.832 MHz AM.
Hoping this can be used for a park-sized hunt once the weather improves :)
Connecting tape measure elements with hose clamps wasn't working well for me. The connections are not very rigid, and the tape tends to snap at the connection.
Here's an alternative that supports the tape measure better, is very strong - and is cheaper :) I'm running the elements through half inch pvc fittings, and securing them by pressing in plugs of pvc pipe. No glue required. It's much more rigid, and if the element ever does break then you just yank out the plugs and add the replacement. It also works nicely for the driven element.
Fox enclosures. Each to hold an HT and a fox controller.
Antenna mount using the standard 3/8-24 coupling. It's durable, but the stainless rod seems dangerous to be left at ground level. Will start with antennas inside the fox enclosures for now. If external antennas are required then will try a flexible element.
Sketch won't upload for some reason, but is available on request.
Prototype of Fox Controller based on Atmel 32u4 and an external RTC module. This one has run for days without any issues.
First version of code is OK to use. It sends 20s of tone bursts followed by a CW message and a CW station id, and repeats each minute. If the RTC is set it will transmit only between the specified start and stop times.
Fox Controller update
Built one version based on a Teensy 3.0 module. It has the advantage of a built in RTC. All you need to do is add a watch crystal. And I had a couple laying around, so wanted to use it. It ran nicely for a couple of days on 3 AAA batteries. But it eventually failed while being scoped. Hmmm... Back to Atmel chips.