In order to not hijack dirknerkles posts concerning the ordering of Ren-WC boards, I am starting this thread. This is intended to be informative as well as a place to get other ideas concerning antennas for both dirknerkles wireless boards as well as FM antennas. I and others welcome all input and thoughts.
On the other thread, DavidHenry was wondering about directional antennas and there were some replies. Here is my further thoughts on this subject.
I am wondering if directional antennas are the way to go. As the name indicates, most, if not all of the power from the transmitter is concentrated in one direction. At these frequencies, 2.4-2.5 ghz, a very narrow beam is easy to obtain. This might diminish the effectiveness of the transmitter, as all of the receivers may not be able to "see" the signal because it is pointed in the wrong direction. It would be better to put the directional antenna on the receiver, but here again, this defeats the purpose of the whole project because a directional antenna is large in size, probably but not necessarily, bigger than the controller and the wireless board combined.
By using the higher power XBee "Pro" version, the necessity of a large, directional antenna is decreased while still providing the coverage most of us will need. As suggested earlier, a vertical gain type antenna, easily obtainable for these frequencies is probably the best bet. Dirk has had very good results with the 1" antenna that is part of the XBee modules. He has also documented his results using these antennas.
I think too many people worry unnecessarily about the "range" of their transmitters, both FM and WIFI. With FM, the distance needed is that which is required to noiselessly cover your property with a few feet thrown in for good measure. With the wireless Ren-W, the range is that needed to provide a good, noiseless signal to the board receivers so that the control data can be transferred with as few errors as possible. The stronger the signal, the fewer the errors.
A good example of the coverage possible with low power and small antennas is my wireless router. It operates on the same frequencies as the XBee modules. I live in a motorhome and the D-Link D624 router is on the floor. It is under a table and next to the wall of a slideout. The transmitter power is 75 milliwatts, if I remember correctly, and the antenna is the short one that comes on most routers.
A neighbor about 200 feet in back of me regularly uses my router for his connection to the internet and has no problems with adequate signal strength. I also use the router from a shed where my dedicated lights computer is located (Control Central!). It uses a USB dongle, hung on the wall and the signal strength is Excellent as reported by the software. This is from over 50 feet away and through several walls.
So, again, the point is: at these frequencies, high power and big antennas and long range are not required. The ability of the system to keep the signal concentrated in the required area is what we are shooting for. If range is increased, this means less power for the units closer to the transmitter.
Dirknerkle has developed a very worthwhile product and has made a huge step in reducing the amount of wiring and cabling necessary for our displays. I look forward to seeing this technology developed even further, as the doors being opened to larger and better displays are many.