Question:
I am a System Admin for Fire Protection systems at the Johns Hopkins University Applied physics Laboratory. We have numerous Anechoic chambers and i was wondering if anyone has had much experience with these. We use the Siemens Cerberus Pyrotronics MXL system and i am designing a system for a new chamber. I intend to mount a control panel on the outside and use Fiber Optic to connect to a slave on the inside of the chamber. this system is going to control a Pre-Action system.My concern is the amount of RF inside the chamber and the effects it may have on the detectors. All of our other chambers are covered by conventional style systems. Any knowledge would be helpful.

Answer: Anechoic chambers come up as topics of discussion somewhat often here, there was a thread going for a while. Where I work, Naval Air Weapons Station, China Lake, we have a few also. The preferred method of detection of late has been the incipient type of detection, where air is drawn into a number of tubes and then passed through detection units outside of the chamber. It is not the favorite type of system, only because of the moving parts, but otherwise works well. I believe the systems we currently have are by "Anitech"(sp?). Since all electronics and any wires are outside of the RF chamber, RF interference to detection units is very low, other than that which might pass into the tubes. Also, detectors inside the chamber, i.e. the addressable Pyrotronics MXL type, will introduce it's own electronic signature inside the chamber, which you probably do not want. A few years ago I came up with a scheme to use polarization fiber to create a strain gage which I was then going to stretch across the chamber and use as type of heat detector, but funding never materialized, so nothing was done with the idea. Please check your chambers for the telescoping head type sprinkler, the one made by Omega was subject to a massive recall and lawsuit, the failure rate was unacceptably huge.