The antenna consists of 1,5mm diameter copper wire pieces. It is a classic yagi design by DL6WU, with a reflector, 10 directors and a split dipole (not a folded one!) as excited element. The elements are so small and lightweight that they can be glued to a small plastic or wood boom (anything but a conductive material). Here is the construction plan for the antenna for download. If you print it to scale you can trim the lenght of the elements and build the antenna directly on the surface of the paper:
http://www.qsl.net.nyud.net/eb4eqa/gsm1800_yagi/gsm1800_yagi.htm
This page presents general information and some tips when using the LM555 timer. Some of these circuits were developed just to see if the concept would work and have no intended purpose.
http://home.cogeco.ca/~rpaisley4/LM555.html
As UHF and microwave RF designs become more popular, you frequently need to “see” what’s being transmitted or received. Most of us are used to observing signals in the time domain with an oscilloscope; however, most oscilloscopes don’t have the bandwidth to see microwave signals. In addition, they aren’t much help in determining what a signal looks like in the frequency domain. This is where spectrum analyzers come in.
http://www.circuitcellar.com/library/print/0406/Armitage-189/index.htm
An operational amplifier, when used as an amplifier, will do everything it can to keep the voltage at the PLUS input equal to the voltage at the MINUS input. That is to say that if the voltage at one of the inputs is increased or decreased the amplifier will adjust its output voltage so that the voltage at the other input is the same as the first. This will be true for inverting and non-inverting amplifiers.
http://home.cogeco.ca/~rpaisley4/BasicOpAmp.html