Radio telemetry is a lot of fun. It is part science, part art and part cross your fingers and hope it works. We try to minimize the later through the use of software studies and site tests. Part of the science is picking the right frequency for a system. When Sterling Engineering Solutions started selling industrial wireless solutions in the late 1990’s everything we did revolved around 900MHz frequency hopping spread spectrum. If the radios did not have enough reach, we put in repeaters. It was pretty simple, especially for our industrial customers with small geographic footprints. Municipalities that cover a larger area were a bit more problematic.
Four years ago, we were approached by CalAmp Dataradio to sell their licensed band IP data and serial data radios. Becoming a CalAmp distributor was a great move for us because it opened our eyes to the wonderful world of licensed data radios. All the radios we had sold up to that point were 1 Watt 900Mhz and now we had UHF capability and a 10 Watt VHF radio in our arsenal. The CalAmp radios were a huge improvement in reach for those larger, spread out systems. It was like growing up with a .22 rifle and later discovering the power and reach of a .50 caliber.
- Since all the radios are always on the same frequency, there is no “Master” radio like 900MHz unlicensed. That single point of failure you have with the 900MHz FHSS can be quite a liability.
- That coax feed line cable used between the radio and antenna eats power, but it eats much less power the lower the frequency. So not only does the frequency cover long distances better, it has more power available at the top of that big tank.
- Line of sight for longer distances is not the Holy Grail with VHF or UHF like it is with 900MHz. The lower frequencies bend better around land masses and can shoot through trees better.
- A licensed frequency is protected for the user by the FCC. Yours truly approves the use of the Federal Government for this purpose.
The only disadvantage is a small fee due every 10 years. The price of the fee is usually offset by lower installation costs since antennas don’t need to be mounted as high with licensed systems.
A word of warning for you existing licensed band telemetry radio users. The FCC is tightening the bandwidth of telemetry licenses. If you are operating at 25MHz bandwidth, you need a new license and maybe new radios good for 12.5MHz bandwidth by the END OF 2012 (http://transition.fcc.gov/pshs/public-safety-spectrum/narrowbanding.html).
Please call us if you would like to learn more.