Communications

oklahoma emergency management vhf radio system

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6.10oklahoma emergency management vhf radio system

Radio frequency 155.235 MHz is the recognized statewide EM VHF radio frequency. It is licensed through the Oklahoma Department of Emergency Management. This frequency is linked in some areas to the OKWIN 800 MHz trunked radio system on talkgroup SEMA-3 using "cross-band" devices. Using certain CTCSS tones or DCS codes in specific areas of the state allows authorized VHF users to communicate with the State EOC in Oklahoma City through the OKWIN system.
This system is primarily a resource for Emergency Managers.
The primary intended use of this frequency is for resource ordering and status updates. It is NOT intended to be used as a tactical frequency, such as for storm spotting or as a wildfire operations net.
How the system works:

When a VHF user keys up within range and on the right CTCSS/DCS of a cross-bander, the transmission is automatically retransmitted on the OKWIN SEMA-3 talkgroup, similar to what one would hear on a repeater, even though 155.235 MHz is a simplex/direct frequency. This is because the OKWIN 800 MHz system is effectively a very-wide-area repeater system. Users on VHF, however, will not hear each other unless they are within simplex/direct range of each other as the cross-banders do not repeat the VHF transmission on VHF.

How to use the system:

Key up your VHF radio and pause before speaking. Then say your FCC call sign and complete unit identifier prior to transmitting your message.

How to tell if it worked:

If your message was successfully retransmitted on 800 MHz, you will receive a “squelch tail” back on VHF. If you do NOT receive the squelch tail:

You are too far away from the cross-bander for it to have received your transmission.

You are using the wrong CTCSS tone or DCS code.

You are on wideband and need to be on narrowband.
The 800 MHz radio was unsuccessful in obtaining a channel grant on the trunked radio system. Occasionally a cross-bander will be unable to access the OKWIN system because of a trunked “system busy”. If this occurs, you will not receive a squelch tail. Wait one minute and re-try your transmission.

The table below lists the CTCSS tones or DCS codes for access to the system. CTCSS tones are used for wideband cross-banders that have not yet been narrowbanded. New cross-banders are narrowband when they are installed and will use DCS codes.

Emergency Management VHF Radio System
Station Location	Channel ID		Channel Frequency (MHz)	CTCSS Tones / DCS Codes
Cross-band Base Stations for Interconnection with OKWIN System
Oklahoma EOC	STEMEOC	155.235 (W)		151.4 Hz
Altus	STEMALT	155.235 (W)		162.2 Hz
Ardmore	STEMARD	155.235 (W)		136.5 Hz
Claremore	STEMCLR	155.235 (W)		141.3 Hz
Oklahoma City	OKEMOKC	155.2350 (N)		251 DCS
Shawnee	OKEMSHW	155.2350 (N)		223 DCS
Stillwater	STEMSWO	155.235 (W)		203.5 Hz
NOTE: Units communicating between mobiles/handhelds and their local EOC or between EOCs should do so in carrier squelch mode if using a wideband channel or use the CTCSS tone 156.7 Hz if using a narrowband channel to prevent the possibility of transmitting statewide on the OKWIN system through a cross-band base station.

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7Recommendations for Programming the Oklahoma Interoperability Channels

If there is enough room in your radio, program all Oklahoma statewide shared channels. For frequencies that are currently used as wideband channels, program both wideband and narrowband channels.
It is understood that many radios currently in use by public safety agencies have limited channel capacity and therefore not all of the interoperability channels can be programmed into the radios. Similarly, some are still not narrowband capable, and the national VHF/UHF interoperability channels cannot be programmed into these radios.
The table below identifies the recommended shared channels in order of recommended priority for VHF and UHF radios.

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Priority	VHF Law		VHF Fire	VHF EMS	UHF
1*		OKLAW1	OKFIRE1	VMED28	UCALL40
2		VCALL10	VCALL10	VCALL10	UTAC40D
3		VTAC11	VTAC11	VTAC11	UTAC41
4		VTAC12	VTAC12	VTAC12	UTAC41D
5		VTAC13	VTAC13	VTAC13	UCALL42
6		VTAC14	VTAC14	VTAC14	UTAC42D
7		OKFIRE1	OKLAW1	OKLAW1	UTAC43
8		VMED28	VMED28	OKFIRE1	UTAC43D
9		OKNET1	OKNET1	OKNET1
* First priority should be the agency’s discipline. (For example, Priority 1 for law enforcement agencies would be OKLAW1 [STATE LAW-wideband]; Priority 1 for fire service would be OKFIRE1 [STATE FIRE-wideband]; and PRIORITY 1 for EMS would be VMED28 [HEARS (EMS)-wideband].)

If your radio has a user-selectable option to enable/disable CTCSS on receive, you may choose to configure this option so that the user can enable the same CTCSS tone used on transmit for receive. The default configuration should be CSQ receive.

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