This page gathers a lot of formulas to calculate waveguide wavelength, cutoff wavelength and attenuation. These formulas are only applicable for dominant mode.
http://df2ck.de/tech/wg/
An output circuit of a helix traveling wave tube was modeled in High Frequency Structure Simulation (HFSS) 3D software. A design change was attempted to make the circuit have a better VSWR than 1.5:1 in the frequency range of 12-18GHz.
http://www.engr.sjsu.edu/rkwok/projects/Report.OutputWindowModel.gurvinder.ankush.pdf
Do you find it difficult to measure height of your antenna tower? No you do not have to climb along it with a measurement tape, Just build this low cost jig and measure height in 15 minutes.
http://www.webx.dk/oz2cpu/ant-height.htm
Anything that conducts electricity is an antenna, (usually a wire, but it could be your body) but the basic unit from which we build antennas is a wire, 1/2 wave length long having a connection in the middle to equipment. Called a dipole, it is an efficient radiator of alternating current electrical energy and is a standard of reference for other antennas.
http://www.kyes.com/antenna/dipole.html
It doesn't take very much wire to pick up an adequate signal for anything but the crudest shortwave receiver.
http://www.hard-core-dx.com/nordicdx/antenna/feed/feed1.html
How to convert a standard book-size battery-powered shortwave receivers to directional reception to reduce interference. Easy construction - can be home-built.
http://www.hard-core-dx.com/nordicdx/antenna/special/reducin1.html
There is significant impedance mismatch between most shortwave antennas and the receiver. With this antenna matching device you will get maximum signal to the receiver at most frequencies.
http://www.hard-core-dx.com/nordicdx/antenna/special/2010ant.html
What causes fading of shortwave signals and what you can do to improve the situation.
http://www.hard-core-dx.com/nordicdx/antenna/special/fencenoise.html