*DOWN UNDER* 1 TTL CHIP TRANSMITTER Price: $0.00 - By Special Request. Please email

The Down Under 1 TTL chip transmitter is a minimalist version of the 2025 FDIM 1 TTL chip Transmitter Buildathon kit. We will be building, testing and modifying these kits during the QRP-ARCI 2025 FDIM Buildathon at the Dayton Hamvention on Friday afternoon. Friday evening, during club night, builders will take their kits into the ballroom and enter them into the FDIM 1 TTL Chip Transmitter Challenge. Rules are posted on the FDIM website but in a nutshell, he whose transmitter outputs the most RF for a 1 minute period wins!

My proposal is to deliver a similar kit that has all the experimentation capability of the FDIM Buildathon kit at a price point under $30AUD mailed to QRPers in Australia and possibly New Zealand. While you won*t be able to enter the FDIM challenge, you can use the kit in a similar on-air challenge down under. Or simply build it for FUN. When I started designing and selling QRP kits 25 years ago, a version of the TTL transmitter was the 1st kit I did so this is coming full circle for me. My kit from 25 years ago used 2 TTL chips, one for the oscillator and a second with 6 open collector gates connected in parallel through DIP switches so it had 6 levels of output power for working various power levels of QRP, QRPp and QRPpp. The current FDIM kit has a variable power supply on board in order to vary the RF output or optimize it at some maximum level. I eliminated that in the DOWN UNDER kit for cost savings on pcb and parts but it you can do the same thing with a variable bench supply or a home brew circuit like that on the FDIM kit. There are spots to plug in a volt meter and amp meter so you can determine the *smoke point* and never go there again! Or you can simply operate it at a lower safe voltage that won*t let the smoke out. We ran last years kits at a little over 11 volts which produced about 1.2 watts. Builders in the the challenge took 2nd, 3rd. 4th and several other places. The winner managed to get 1.8 watts of RF out of a similar design.

I just tested this design on my bench and it produced .25 watts at 9 volts input. With a maximum voltage and some heat sinking, it should be in the 1.5+ watt range at some as of yet undetermined operating voltage. I will be playing with it on the bench in the next couple of weeks. The image included here is the DOWN UNDER kit with MY builder supplied power and RF output connectors. I use RCA jacks on most of my tuna can kits so jacking into my RF power meter is easiest for me with an RCA output. Likewise, I have a nice little switched output bench supply normally hooked up to a 2.5mm barrel plug for 9 volt power. The builder needs to supply those connectors compatible with their bench equipment.

I hope to make arrangements to have this Down Under kit kitted and mailed WITHIN AUSTRALIA and possibly NEW ZEALAND. I will make them available for purchase if I can pull that off. It should make a nice inexpensive group challenge project.