Click on images to enlarge                                       All about the DRO  by John VK4TL                                      (Dielectric-resonant Oscillator) Some twenty odd years ago I became interested in Gunnplexers. These are devices which depend on a special diode which will oscillate at very high freqencies. The inventor was a professor named Gunn. When my sister was about to visit from USA, I asked her to bring my purchase of gunnplexers over. Imagine the cutoms concern at the mention of a name with gun in it. I imported two, one of which was for VK4AFC. Over the years not a lot has been acheived with these and they are very unstable. Hard to tell when you are in the band.  Also available are door opening gadjets and alarms using these diodes and so some units were built for local hams to enable QSOs with contest stations here in the north. Considerable success has been achieved. There is a newcomer on the field which promises a much better performance with the same simplicity and that is the DRO. This is a transistor oscillator with a ceramic "puck" coupled to it which is ten times more stable than a gun oscillator. With the gunn we had to use very wideband IF stages otherwise we would lose the signal due to drift. So ten times better than an FM broadcast receiver means a tenth of that bandwidth. That is 200 Khz divided by ten and so 20 Khz. Now ordinary two way radios used to be 30 Khz. Using the 10.7 Mhz IF from a two way modified with a wider xtal filter will give us much better performance than the old gunn osc. Two units are set up and due to be tested soon. If you look at the picture of the $5 DRO from China you will see two antennas for rx and two for tx.Also note the size. These can be cut off, and the in and out from the unit channeled through coax to a switched parabolic antenna. At present a cylindrical parabola reflector is in use so that rx and tx beams are parallel Further information and product availability on 10ghz DRO’s can be found at www.shfmicro.com