1. Public Safety Radio System Narrowband 101

2. What Has Changed?
The National Telecommunications & Information Administration (NTIA) “refarmed” frequencies used by government agencies.
As a part of refarming, each 25kHz wideband channel was divided into two 12.5kHz narrowband channels.
There are now twice the number of available frequencies.
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3. When Did the Change Occur?
In 1995, Congress mandated that all federal agencies transition to narrowband frequencies by January 1, 2005.
In the future narrow banding will continue to be the standard:
By January 1, 2013, the FCC will require all to be narrowband.
When technology permits, each 12.5kHz frequency will again be divided in half, resulting in an even narrower frequency of 6.25kHz.
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4. Why the Switch to Narrowband?
Increase the number of available frequencies for general use.
Where there was one frequency now there are two.
Increasing the number of usable frequencies reduces frequency congestion.
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5. Bandwidth Comparison
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6. Wideband vs. Narrowband
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7. Look at it Another Way
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8. Wide to Narrow Channel Split
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9. Radio Capable Narrowband?No
Kind of
Can work on “Some” narrowband channels
Yes
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10. Why New Radio Equipment?
Narrow banding halved a frequency’s bandwidth and deviation.
Many older wideband radios could not operate on frequencies set 12.5kHz apart. They could only be set to frequencies 25kHz apart.
An older wideband radio’s bandwidth is 25kHz wide. This would interfere with both new 12.5kHz narrowband frequencies on either side of the old 25kHz frequency.
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11. Narrowband Communication on a Wideband Channel
Received audio may be very soft and quiet.
Caution, wideband radios must turn up volume to hear. However, once a second wideband radio transmits, the original wideband radio’s received audio will become very loud.
Audio may not be picked up (processed) by wideband receiver.
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12. Wideband Communication on a Narrowband Channel
Received audio may be loud, distorted, or inaudible.
Communications may work at a distance but no audio may be received when close to receiver.
Usually the cause of mixed band communication problems.
Caution, if you turn down the volume, narrowband communications may not be heard.
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13. Avoiding Problems Do not operate in a mixed band environment.
Only use narrowband or wideband on a Per Channel Basis.
Issue narrowband capable equipment to those with wideband only equipment.
Establish reliable communications before entering the field.
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14. What Should You do? Use Different Tones for Wideband and Narrowband
Keep Informed
Iowa Statewide Interoperability Communications System Board
Know What Your Neighbors are Doing
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15. What Doesn't it Mean? Have to Switch to Digital Have to use P25
Have to Move to 700 MHz
Narrowband ¹ Interoperable
The State is Taking Care of All This for Us
The County is Taking Care of It
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16. What to do with Your Old Radios?
Newer Programmable Radios
Wideband Only
Can be Used by Amateurs
Donate to Local Hams
Contact Us, We Will Take Them
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