FREE Radio Frequencies The ISM (Industrial, Scientific Medical) band was made available for low power, unlicensed radios to be used in, Industry, Science and Medical communications. These FREE frequencies have been a boon to industry. With these frequencies we have seen an explosion of devices made specifically to work in in SCADA, Hospitals, Garage Door openers, Cordless phones, Microwave ovens, Bluetooth, and on and on. GREAT, it has helped the world become better connected......It has also filled the air with radio signals and these signals interfere with each other. A few years ago, you could put one of these systems into place and all seemed good. Then you started to notice loss of signal from a few sites, so your techs added gain to the antenna to give you more power, but they also broke the rules at that time. These frequencies are limited to a max power output and the power is measured at the ANTENNA . When you add more GAIN to the antenna, you increase the effective radiated power (ERP). When you do this, you now interfere with someone else radio and what do they do? The same as you did, they add gain to their antenna, raise it higher and now they are interfering with someone else's system so they do the same, and so on and so on .... |
