Aeronetworks sro - Airborne Linux

While playing with my milling machine and little microwave PCB Yagi antennas, I wondered about increasing the bandwidth and still getting directional gain.  A Log-Periodic antenna looks almost exactly, but not quite unlike a Yagi... Practice is the best of all instructors -- Publius Syrus On a Log-Periodic, all the elements are driven, but each dipole is reversed by 180 degrees.  To make it on a single sided PCB, will require some links to wire up the dipoles.  I added a BNC connector and thin equilength coax to the feed points of the antennas. Stacked Log-Periodic 5GHz To reduce the amount of copper that needs to be milled out, I cut the board close to the radiators.  The bar at the back is for mounting and also serves as a reflective ground plane.  A log-periodic antenna is surprisingly compact and a little 5 dipole antenna will have a gain of about 3 dBi.   By carefully stacking two of them 0.75 Lambda1 centre to centre (54 mm), one should g...

When you need to test two radios in a lab, they are awfully close together and may not work over the air, since the transmitter will overdrive and saturate the receiver.  You may even damage the receiver since the radio front end is very sensitive and the transistor features are extremely small.  If you would accidentally touch the antennas of two radios together, you could instantly melt the receiver front end. DIY 90 dB(?) Attenuator To avoid this melt-down problem, military manpack radios are usually built with power transistors on the front end - the same ones used in the power amplifier.  Since power transistors are expensive, commercial radios are usually not so rugged. Path Loss If your transmitter operates at +30 dBm (1 Watt) and the receiver has a sensitivity of -90 dBm (1 nano Watt), then to work properly, you need a path loss of 80 to 90 dB, to bring the transmit signal down to a safe level of about -60 dBm. You can then hook the two radios back t...

PCB Mill Kit My latest toy is a small PCB Mill, a CNC 3018 Pro, there are many available from Ali Express for the enormous sum of 285 Dirhams or so, which is about 70 Euro.  I thought that even if it didn't work at all, it would not be a big loss. Assembled CNC 3018 Kit It will help if you have a little previous workshop experience, but these machines are so simple and relatively slow moving, that any radio-geek can safely experiment. Carving With a V-bit in a Puddle of Oil Of course I can have boards made in China by Dirty PCBs , but what is the fun in that? The problem with making PCB antennas, is that you need to experiment to change the design 1 mm this way or that, to tune it just so and just such and having to wait 2 weeks for each experiment doesn't work.  A few hours playing with a router is more practical. It turned out to be a pretty nice little kit, made from aluminium and 1/4 inch Bakelite (paper reinforced phenol formaldehyde).  This Pre...