Over the past few years there have been a lot of new stories about problems with police radio systems. Complaints about noise, drop-outs, and sometimes a complete failure of the system are often cited in these articles. In some cases, the issues are caused by substandard equipment, poor planning, and poor installation. But other times all of these are ruled out, and yet the system remains problematic.
What then is the cause? A while back the City of Oakland, which has been plagued for years by failures of their police radio system, pointed the finger at cellular carriers as the culprit. Oakland PD's radios are very close in frequency to some of the cellular bands, so it makes sense to investigate this. And in fact, when the cell sites were turned off the problem went away. So is the problem with the cell site, the police radios, or both? Certainly there are some radios on the market which have poor receivers and are likely to pull in radio signals from cellular bands. But lately I've been working with a team of consultants on analysis of these cases which shows that over-crowded cell sites may in fact be contributing to the problem.
Securing the permits, regulatory approvals, and community support for cell site construction is a huge problem for the cellular carriers. So when they find a site, they tend to load it up with as many systems as they can. The problem is that the signals can mix with each other and create very fast transient high noise floors near the sites, even outside the cellular bands. The more systems sited close together, the more likely it is that this will occur. So while cellular may seem like a God-send to churches, they should be careful to avoid overcrowding - or there might be hell to pay in the long run.
