Shortly after Christmas, I finally got around to building and mounting my revised LZ1AQ amplifier for a wideband loop. My previous PCB design contained less features and required an outboard cable connection.
When I designed a new PCB using PCBGoGo last fall, I made several modifications.
First, I added a shielded RJ45 jack to the PCB, shown lower center above. I purchased a bunch of these 8P8C connectors on e-bay for about 60¢ each. The only downside was that I needed to design a custom footprint in KiCAD, but that was pretty easy. I use one pair for power and a second for signal.
Second, I added a voltage regulator to my revised LZ1AQ amplifier board, shown lower right. This provides a stable, filtered 10 volts for the amplifier, which draws less than 150 mA. I used the Microchip MC1804T, which costs about $1 from Mouser. By taking this approach, I can just feed a standard 13.8VDC to my loops and worry about the operating voltage on the PCB.
Finally, I replaced my DIY ferrite core transformer with a Coilcraft WB2-1T, shown center above. This miniature 2:1 transformer works from 70 kHz to 400 MHz and costs around $2.50. You can easily mount these in a 6 pin DIP socket, as I did above. Insertion loss is around 1 dB.
The rest of the amplifier components are unchanged. My new approach also uses a standard 40 by 60 millimeter PCB size so I can try different amplifiers within the same loop housing.
Revised LZ1AQ Amplifier – Cold Weather Performance
Recently, we have been experiencing a spell of very cold weather in Calgary. Temperatures have been steady in the -30° to -20° C range plus the dreaded wind chill. The loop worked fine.
When I ordered components, I made sure all of them were rated to -40° C. The SMD 2N222 transistors are actually rated to -55° C. Something to keep in mind if you live in cold climates.
Lastly, the structural parts, 3D printed using PLA, have held up nicely, as well.