Replies to This Discussion

Permalink Reply by Peter von Bergen on July 28, 2010 at 3:04pm

Digital Radio is very different from Analog Radio and it has lots of problems - especially for the Fire Service.

If you like the way your cellphone works, you will like digital radios. I don't have much faith in my cellphone nor in digital radios on the fireground or police department. Besides the problem with noise interference from the very items firefighters are expected to wear and carry, digital radios are so reliant on computer software and hardware to make them work that they often fail to understand what is expected of them. Classic example was FDNY's early experiment with digital where the company approaching the scene could hear the call for help from an officer in the fire building but the others on the scene could not. Go figure. If an analog radio is putting out a weak signal it can be heard, though often scratchy and with difficulty. If a digital radio is putting out a weak signal (or is far enough away or behind a wall or whatever) it probably won't meet the criteria programmed into the computers so it won't be heard at all, period.

When my cellphone operates as well as my landline, I will suspect digital radio might be better too. Until then, uh-uh.

Permalink Reply by Brian Michel on August 11, 2010 at 12:22am

My department went to 800mhz system a few months back and there has been one problem after another. First is that they had to design a call box for the station to activate the loud speakers during a call for that station. If you have ever worked a cell phone with ptt it is basically the same principle, you press and wait for the beep (kinda hard to hear a beep while in a house fire dont ya think) there is no easy way to switch to a simplex or a talk around channel as required by NFPA. We had our radio lose 5 of 7 channels so calls were getting qued while trying to transmit. Dispatched calls were not heard and response was considerably delayed. When the bugs are worked out the system will be only as good as our previous VHF radios.

Permalink Reply by George A. Laiacona III on August 11, 2010 at 11:07am

Some things to keep in mind while discussing radio issues: The higher the frequency, the more line-of sight is the radio. So, if your closest repeater for your shiny new 800MHZ radio is miles away on the back side of a hill, you'll get poor signal.
Digial radio systems today require a pretty good signal to be of any use.
Metal interferes with radio signal. Even stuff like chicken wire or wire mesh would be sufficient to knock out a signal, depending on frequency. And as I recall, some construction techniques use wire mesh as a backing for plaster, in new and old buildings alike.
Just because it's new and fancy doesn't make it suitable. But you can't always get that through to the planners and buyers.
By the way, I'm also an Amateur radio enthusiast. KI4PKI

Permalink Reply by Daniel Luechtefeld on August 19, 2010 at 4:51pm

Do not confuse "800 MHz" with "digital".

Most 800 MHz systems are FM, meaning analog.

Many of the next generation systems will be hybrid digital-analog FM systems at 700 MHz.

Digital systems are very good for some functions; some outperform their FM counterparts in areas such as range and intelligibility. However, they're not quite ready for fireground use.

Make no mistake - that day is coming. Several years ago the FCC issued a notice encouraging licensees to consider migrating to systems using 6.25 kHZ wide channels - FM will not work on channels this narrow. The only existing 6.25 kHz systems are digital.

Daniel - K7DGL