DHS Wideband FM Freqs?

[eraweeb]

I hope I am posting this in the right forum, I apologize if not.

From the RR Wicki I downloaded a PDF titled, "National Interoperability Field Operations Guide - May, 2009."

It is supposed to be a field guide for radio techs responsible for programming radios in disaster and emergency situations. How's that for some dry reading? Anyway, in some of the frequency tables they instruct these techs to NEVER program CTCSS into "receive only" channels and to use CSQ only. I wonder why since most people I know program the CTCSS into their "receive only" scanners.

Also in other frequency tables they say to program VHF Marine frequencies and several VHF SAR frequencies in the 155 to 157MHz band as Wideband FM. This obviously is just the opposite of the norm as far as I know.

Can anyone shed some light on this for me? Thanks in advance!

[kd7kdc]

For the first question, the reason is so the field units do not unknowingly transmit on top off
another agency/user on a different PL because they can not hear them if CTCSS RX is enabled
with code A they will not hear anyone else running a different code or carrier squelch.
The KISS principal.

For the second question, the reason is probably the majority of the radios still out there in those
two or at least the Marine band is still wideband and I don't see the maritime radios going narrow
anytime soon. For SAR it is probably a catch all because there are a lot of teams that are mostly
low budget volunteers that get hand me down equipment or have to buy their own.


So far as Nationwide narrowband, compliance is not required until 2013.

73
Steve

[rvictor]

Originally Posted by eraweeb

Anyway, in some of the frequency tables they instruct these techs to NEVER program CTCSS into "receive only" channels and to use CSQ only. I wonder why since most people I know program the CTCSS into their "receive only" scanners.

Since you are talking about programming for emergency communications, I would think that they don't want CTCSS on the receive channels because it would keep you from hearing someone with an emergency that might not have the proper code programmed into their transmitter. CTCSS limits what you can hear which would seem to be just the opposite of what you'd want in that circumstance.

Dick

[milf]

Maritime is for interop with USCG, USMC, USN SAR teams. As the maritime is international to a point, you will not be seeing that band going narrowand for a while.

[nd5y]

Originally Posted by eraweeb

Also in other frequency tables they say to program VHF Marine frequencies and several VHF SAR frequencies in the 155 to 157MHz band as Wideband FM. This obviously is just the opposite of the norm as far as I know.

Can anyone shed some light on this for me? Thanks in advance!

I case you don't already know this, when that guide says "Wideband FM" they are talking about normal 20 KHz bandwidth FM and not 200 KHz bandwidth broadcast/TV FM. Unlike scanners and some ham radios, there are no part 90 two way radios that have broadcast FM receive capability.