... and maybe a few other things. Ever wonder how to wind a binocular toroid? I'll show you how in this one. I found this part of the build confusing, but I got it figured out and I'll share with you in this part of the build:
Binocular describes the type of coil form. Bifilar describes how the wire is twisted together prior to winding in other transformer designs. The QDX uses a Binocular toroid for the power transformer. There are no Bifilar windings on it. Dave W7UUU
I grappled with the 9v and 12V options but wanted to keep things as simple as possible and run low power WSPR. I wound my Binocular transformer for 12V for several reasons. 1)Direct power from any of my many 12v supply options and 2) also wanted lower power for running WSPR powering it from 7v. Mine puts out 4w or better on all bands at 12v and will put out around 1w for band hopping WSPR at 7v. I never saw any data on how much power the QDX would run if the voltage was reduced to 7v when wound for 9v. (7v is about the lowest you want to go for the 5v regulator to function properly) Been happy with the decision ever since and use a simple buck switcher (about $4 on ebay) with a switch to go from 12v to the output of the switcher which is 7v if I want to WSPR which is alot of the time. The QDX barely gets warm in the 1w WSPR mode and runs most nights on 20-80m with an 8 minute duty cycle into a non resonant antenna on 80 and 30m without issue. I have accidently transmitted into an open and short and didn't hurt anything FWIW. I run the crap out of it on FT8 without worry at full output. The Trifiller transformer is even more fun! I see QRP Labs has said he is working on a high band unit and I will jump on one of those when available! Also the rev 3 low band units will be coming even sooner. 73 -Mike
Same here, I read the Groups.IO forum with interest and earnest and couldn't really come up with a solid reason to do 12v other than my shack runs at 12v... There seemed to be more wattage and better safety at 9v, so I went with 9v. I can always change it later, since its a kit and has great instructions, I now know what it takes to do that kind of thing. I love learning through building useful kits.
Thanks for posting the video. It's always nice to see people building their stuff. Btw. TCXO stands for Temperature-Compensated Crystal Oscillator. 73. Michał
Perhaps Steve, when you get it up and running, you could turn the voltage down to 7v and see how much power it puts out... The driving force for me was the low power WSPR(~1w) to set it up for 12v operation. Otherise, I would have set it up for the 9v operation. I am surprised there is not much interest, at least here with these little gems. Hans at QRP labs said the rev 3's will be out in 5-6 weeks and he will produce 2000 kits this time. Best value in digital Ham Radio today IMO! 73 -Mike
