Narrow Banding reception on older scanners?

[rangercurt]

I'm new to this forum, so bear with me if I missed this topic in a search. I live and work in Santa Clara County, and with the narrow banding of VHF frequencies happening in Dec '10, how will this effect the reception on existing scanners? Our agency has older scanners (greater than 15 years old) and I'm wondering if they will still receive clearly when this change happens. I asked this same question to our primary radio tech, and they didn't know. I've also posted via twitter, and had someone reply that reception is quieter (less gain?) than the wide band. Anyone else know?

 

[nd5y]

Listening to narrowband (2.5 kHz deviation) on a receiver set to, or designed only for, wideband (5 kHz deviation) will make the audio output about one half of what it would be on wideband.

 

[W2NJS]

You may or may not notice a perceived difference in the level of the audio, depending on several factors. And if your receiver is one of the older ones you may begin hearing two stations at the same frequency setting. Years ago I had a Regency VHF transceiver that was pretty widebanded, so much so that it would receive FDNY Manhattan and either a Newark or Jersey City NJ FD channel which was 15 kHz away from the FDNY channel on 154.25. I changed out the Murata filter in the radio to a narrower bandwidth which quickly solved the problem.

 

[n0nhp]

At best you will have a quiet channel, At worst the narrrowband frequency you are trying to listen to will be a "splinter" frequency and your scanner will round the frequency to the nearest 5KHz channel. The audio will probably be ok even receiving the rounded frequency but as others pointed out, you may receive multiple signals.
For regular analog narrowband reception, there are a number of analog only scanners on the market for very reasonable prices that have the narrow filters installed and the splinter frequencies available.
Give the old scanner a try and put some money back for a new scanner. The rules are going to force everybody narrow band before long.

Bruce

 

[kb2vxa]

What they said.

"At worst the narrrowband frequency you are trying to listen to will be a "splinter" frequency and your scanner will round the frequency to the nearest 5KHz channel. The audio will probably be OK even receiving the rounded frequency but as others pointed out, you may receive multiple signals."

This one caught my attention as there usually is a fix for "bleed over". I had that problem with an old scanner so I shifted the frequency up or down as appropriate to put the offending splatter out of the IF passband. Still you'll need one for NBFM eventually as the bands fill up making frequency shifting useless.