I would recommend reading appendix A of my master's thesis :) https://ecommons.cornell.edu/bitstream/handle/1813/8346/thesis%20formatted.= pdf?sequence=3D1&isAllowed=3Dy It is an 11-page summary of antenna theory (that I had to include because my thesis advisor was not an antenna expert) With an efficient passive antenna (no amplifiers and no major losses that you can reduce), you can't get more gain without being more directive. In other words, if you cannot be directional, then making your antenna bigger than a half wavelength does nothing for you. This is true for BOTH transmit AND receive because passive antennas are reciprocal devices. A patch antenna is probably best for you. Any kind of linear antenna is going to have a null along the long axis of the antenna. This can be a problem for the case where the robot is on one floor and the operator is on another floor. Colinear arrays only make this worse - they direct more radiation in a flat disk and have an even wider null along the long axis. They are commonly used for cell towers because all of the cell phones that need to access the tower are in a narrow range of vertical angle - radiation going up into the sky (or listening for radiation from the sky) is a waste. Sean On Wed, Jul 11, 2018 at 2:37 PM, Neil wrote: > Okay antenna gurus, I can use some help here please... > > I'm using a 5.8Ghz video transmitter/receiver system on a robot (2D > driving, indoor). These systems are popular with the drone-racing > crowd, but most of the good antennas are either circular-polarized (so > they are uniformly effective at most angles) or patch antennas which are > apparently very unidirectional. Linear antennas have mostly gone away > for this purpose. > > I'm trying to maximize signal strength/reception so the operator can be > in a different room and on a different floor. For my purposes, I'm > thinking a linear antenna on the transmitter side (robot) may be best > though, as I can mount it vertically in the robot body, and perhaps use > a patch antenna on the receiver side as that would have minimal > movement. Or linear as well for the receiver. I understand that whip > antennas are really crappy so would a straight piece of wire work > better? I also discovered "collinear antennas" while searching. > > I have about 18-20" of room to put an antenna vertically inside the > robot ... would having an antenna length of a multiple of the wavelength > work better than just a single-wavelength antenna? > > So what say ye? > > Cheers, > -Neil. > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .