My BCT-15 comments
Hey guys, I didn't realize this thread was here or I would have been on sooner. My name is John Wheeler, I work for NBC News (both the network and the local station KNTV which is owned by NBC) here in Northern California. I drive and am the engineer for the San Francisco Metro satellite uplink truck. When I'm not assigned, my (voluntary) duties include monitoring all the fire departments (22 or so of them) in the Bay Area.
To do that, I have a bunch of scanners. In our San Jose facility, we have 12 BC796Ds, In San Francisco, we have 8. Here at my house, I have 10 scanners, which include every vintage all the way back to a PRO-2006.
I'll admit I'm an audio quality nut; I have an Emmy Award for television sound. I'm also the developer of the Penteo(R) process which upmixes stereo to surround professionally.
I wanted to throw in my two cents about the BCT-15. Although I think it has tremendous potential, I have had to revert to a BC895XLT as my primary monitoring scanner in my truck. The problem is purely audio quality. Apparently the BCT-15 is using DSP, and there seems to have been a real attempt to knock the frequency response down to something like 5kHz. Of course with bandwidth that low, there are two problems: the sibilants that make speech intelligible get significantly chopped away. In addition, that filtering makes any picket-fencing (RF dropouts when driving) turn from simple swooshes into noisy crackles. The crackles are then louder than the modulating audio.
I also was very disappointed in the AGC, which is so timidly implemented that I almost can't tell when it's turned on. Fortunately I found the AGC tweak instructions for the 396T and found that they also work in the BCT-15. In looking over the notes, I have to say that this is not a place where one needs to be concerned about AGC "pumping": I want it to pump. This ain't classical music, it's speech. We want to hear every syllable clearly as possible, and the only way to do that is to compress it down to the same level as a typical AM radio station, having no more than about a 6db variation in modulation (outside of silence, of course). I found that by maxing out the range and minimizing the attack time the AGC actually works!
(Here in the Bay Area, some departments have well maintained radio systems, and some don't. The differences in modulation levels between departments are dramatic among 22 different departments, some of which are EDACS, some Motorola, and some 1960s vintage low-band FM. Some dispatchers are on headsets, and some are using desk mikes. I wish the public safety communications industry would adopt some of the same audio processing techniques (like the Optimod AM) which makes AM radio so intelligible on commercial stations. But I digress.)
Is there any way to open up the frequency response so that it approaches a traditional scanner? I can see a 8kHz to 10kHz filter to eliminate the out-of-bandwidth noise, but the one in the BCT-15 is just set way too low. How about filtering out the CTCSS tones while we're at it?
Anyway, that's my two cents.
-John Wheeler (newstruck)
