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A crossband system has the ability to work on different frequency bands, as well as frequencies within the same band. The repeater can receive from a user, link to another repeater and transmit to a different user, all on different frequency bands or frequencies within the same band.The basic crossband repeater utilizes frequencies with sufficient seperation, typically on two different bands, to avoid internal interference. An unattended station working in this way is a radio repeater. It re-transmits the same information that it receives.How can I legally make my VHF/UHF station into a crossband repeater?Ham radio VHF/UHF crossband repeater operation is a common use for amateur operators. The crossband repeater translates back and forth between a 2m simplex channel and a 70cm simplex channel. The weaker 70cm transceiver, often a HT, can work through a mobile or base station to communicate with a 2m simplex net, taking full advantage of the mobile or base transceiver higher power or higher antenna elevation. Any dual-band or dedicated 70cm HT can be used to operate through a cross band repeater. One example of cross band repeater usage:<BR>[[File:cbr-fig1.gif]] ==Selecting a Frequency Pair==Pick your frequency pair carefully, so as not to cause harmful interference to other users. The use of cross-band repeaters has the potential to cause serious disruption of communications circuits, and the creation of harmful interference to coordinated repeaters. If you are not sure of active repeater frequencies in your area, a safe rule is to stay off of the repeater sub-bands and use the FM simplex portion of each band. You should consider using CTCSS on the frequency your transceiver lists on for your mobile input. This will help prevent your repeater from broadcasting unwanted transmissions coming into the input from interference or distant transmissions during periods of unusual band propagation. ==How can I legally make my VHF/UHF station into a crossband repeater?==According to an article on [http://www.jpole-antenna.com/ KB9VBR] called [http://www.jpole-antenna.com/2014/05/01/cross-band-repeater-operation/ Cross-Band Repeater Operation], "''Kenwood’s TM-V71A and TM-D710 now have the ability to identify the outgoing UHF transmission.''" This article also goes on to explain very well the legal issue with cross-band repeater operation. Here is a quote, <small>"''When you transmit, you identify your transmission with your callsign. The incoming UHF transmission is identified, and the outgoing vhf transmission is identified, since you are the control operator of your handheld radio and of the cross-band transceiver. On the other side of the transmission, the repeater identifies its own transmissions. That transmission is then retransmitted by the cross-band transceiver on the UHF channel. But this UHF transmission does not have your callsign attached to it, so it’s an unidentified transmission. Most cross-band repeat capable radios are designed with this fault.''"</small>==Duty cycle==Most radios aren’t designed for 100% duty cycle and constant use of the cross-band repeat function can damage the radio. The final stage transmitter amplification transistors will overheat causing them to fail. For example, the [[Tytera TH-9800]] has excellent cross band repeat capability, however, it also gets very hot after 30 minutes of use even on the low power setting. Long term use of transceivers like this will inevitably result in premature failure of the final stage.==resources==* [http://www.arrl.org/auxiliary-station-faq Auxiliary Station FAQ on ARRL]* [http://www.jpole-antenna.com/2014/05/01/cross-band-repeater-operation/ Cross-Band Repeater Operation, KB9VBR J-Pole Antennas][[Category:Electronics]][[Category:Consumer Electronics]][[Category:Radio]]