Cross Band Operating Options for Wide Area Only and Wide Area and Local Area Operations Mike Duff NY2PM

What is Cross Band Operation? Cross Band Operation is a function of a Dual Band Radio wherein the two radios are tied together such that a signal received on the first radio is re-transmitted by the second radio and vice versa.

Why Cross Band? Cross Band Operation creates a gateway for other radios accessing the Cross Band Radio to utilize frequencies, modes or power not available on the native radio.

Examples of Cross Banding A Mobile Rig may be put in Cross Band Operation with a Handie-Talkie to allow the driver to access a repeater unreachable from the Handie-Talkie when he / she is out of the vehicle. A HF Base Station Rig may be put in Cross Band Operation with a VHF Mobile Rig to allow access to a HF net while operating from a vehicle.

Why Are We Cross Banding ? We are Cross Banding because the Hospital Radios are not in the Command Post or Logistical / Communications areas. The radios are in penthouses and odd offices / closets. The Radio Operators need to be in an area where they can pick up and deliver messages to Incident Command personnel. Since the Radio Operators and their radios are separated, a link needs to be established between the two. This link will be via Handie-Talkies which will not have the power for Wide Area Simplex Communications. If the Radio Operators and their Base Station radios were together, there would be no need for Cross Band Operation.

Wide Area Only Via Simplex If the only concern is to enable Radio Operators to connect to each other over a Wide Area circuit, then the following scheme can be used. UHF or VHF can be used on the Handie- Talkies as desired. VHF would be preferred for the long haul circuit.

Wide Area Only Via Duplex If a repeater is available, it can be substituted for the long haul VHF Simplex circuit. The Handie-Talkies operate in Simplex mode while the Cross Band Radios operate in both Simplex and Duplex modes. In a severe situation, repeaters may be unavailable.

Wide & Local Area Via Simplex If the Local Area of operation for each hospital is too large to support direct local communications between Handie-Talkies, then the Handie- Talkies may be operated in a Dual Band configuration to provide reception of the Cross Band radio’s Wide Area transmit signal. This makes the Cross Band radio function as a Wide Area link and a Local signal booster simultaneously.

Wide & Local Via Simplex Local in range conversations can be conducted strictly on the local area VHF channel. Wide area communications use the cross band radios to access the wide area UHF channel. Users in the same local area that are out of range of each other can communicate by monitoring the local cross band radio’s wide area UHF channel. Reception of the UHF channel should be muted during VHF transmit to avoid a feedback loop. If simultaneous reception of the VHF and UHF frequencies presents a problem, the VHF channel can be permanently muted. In this case, local communications are made over the local cross band radio’s “boost” channel but local HTs must be able to hear the distant cross band radio’s UHF channel to receive distant users.

Wide & Local Area Via Duplex The wide area circuit can also be a made via a repeater by setting one side of the cross band radios to duplex mode. We come to a difficulty though if simultaneous reception of the VHF and UHF frequencies presents a problem. In the Wide & Local via Simplex scenario we could mute the VHF channel permanently and receive both local and wide area communications over the UHF channel. In this duplex scenario though, the local UHF “boost” channel is different from the incoming UHF wide area channel. Muting the VHF channel would block incoming wide area communications. Therefore, if simultaneous reception presents a problem then the local “boost” option must be abandoned in duplex wide area applications.

Which is Best? Each of the preceding scenarios may have benefits in different circumstances. A good strategy would be to program each of the four scenarios into your particular radios and then test each one to verify expected operation. A cross band radio with “Hyper” memories could then be used to call up any particular scenario.

A Few Words of Caution Whenever cross banding to another system, protect the input channels on the cross band radio with CTCSS or DCS control tones. Be careful of power settings and duty cycles on the cross band radio. It is not a commercial repeater. Stay in local control of the cross band repeater as remote control of a repeater requires a separate third channel which is not available on simple cross band radios.

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