KNW-107
Cross Band Repeating
Crossband Repeating is the process where a Ham transmits a low power signal using one band (UHF), to another radio with a better antenna and higher power output. The other radio then re-transmits (VHF) to a repeater or other far away radio system. This is very handy when you need to use a HT for mobility or in low lying areas but cannot reach the end destination with the HT because of distance, tree cover or higher surrounding terrain. Using your HT along with your mobile rig can solve this problem.
This training will cover this topic in a general way since the Crossband Repeating setup is very dependent on the specific equipment used and your specific needs.
Not every radio can support cross-band operations. Things to look for in the selection of mobile radio capabilities for use in Cross-banding are:
- Tone squelch
- Split sides
- Split tones
- Remote control
- Cross-band capable
CAUTIONS IN USING CROSS-BAND
Never crossband between two repeaters. This can cause both repeaters to remain transmitting and make the system unusable for everyone. Always use tone squelch to prevent a radio from receiving a signal and re-transmitting it unless the PL tone is received. Your crossband radio will become part of a repeater system so you need to ensure that any random input signal to your cross-band rig does not enter the system and get re-transmitted. If you are part of a formal net, ensure that you get a UHF o VHF frequency assigned to you from NET Control so that you do not interfere with another Amateur operator close by using the same frequency. Also refer to the band plan for your state for each frequency.
Remote Control of your cross-band rig from your HT is handy to shut off your cross-band repeat if necessary. Study the specifics about your radios to set this up properly.
Split Sides/Split Frequencies: some dual band radios (mobile or HT) can transmit on VHF and receive on UHF or vice-versa on the same side of the radio. Typical radios can have one frequency on the left side (UHF), and a different frequency on the right side (VHF). A few radios will allow you to program a VHF frequency on one side, and create a split so the same side can re-transmit UHF.
Split Tones: Some radios also have split tones. For example transmit a PL tone but be configured with a different tone squelch.
Power Supply: Be sure to have enough battery power and adequate cooling because your mobile radio may get heavy use during an assignment with lots of radio traffic and especially if it is being used by multiple HT stations in the vicinity.
Types of Cross-banding
In a nutshell, in half duplex you transmit via your HT to your mobile, cross-band repeater which re-transmits your signal to the main repeater but any signal from the main repeater is NOT re-transmitted by the mobile, cross-band transceiver, it is received directly by your HT thus reducing the load on your mobile radio’s output power transistors. This can be problematic where HT location affects reception from the main repeater.
Half Duplex is the easiest to set up. This is where you transmit simplex from your HT to your cross-band repeater using UHF or VHF and your cross-band repeater re-transmits to the main repeater via VHF or UHF (depending on the frequency being used by the main repeater at net control). When you stop transmitting from your HT your mobile radio stops transmitting. This is used where you are close enough to the main repeater to receive the repeater signal directly on your HT.
Half Duplex set up:
1. Configure your dual-band HT to transmit UHF with a PL tone.
2. Configure the HT to receive the main repeater VHF frequency.
3. Set your mobile radio to receive on UHF with the same PL tone as set in 1 above.
4. Set your mobile radio to re-transmit on VHF with the main repeater PL tone.
5. Place the mobile radio in cross-band repeat mode. HINT: Set LOW power to conserve power and reduce heat.
Now, when you key up your HT, it will transmit on UHF to the mobile. The mobile, hearing the proper signal, and the proper tone, will open, and re-transmit the signal on VHF with a PL tone but your mobile will not respond to VHF from the main repeater or re-transmit it via UHF to your HT.
Full Duplex cross-band repeating is more difficult to setup. If your situation allows, use Half Duplex. In Full duplex your radio will be working almost 100 percent of the time since it transmits in both directions. Only use this setup if your HT can not hear the main repeater directly and consistently.
In full duplex, when you key up your HT, it will transmit on UHF to the mobile. The mobile, hearing the proper signal and the proper tone will open and re-transmit the signal on VHF with a PL tone. When the main repeater transmits on VHF, the mobile re-transmits the signal from the repeater via UHF to your HT using the proper private tone (use low power).
Full Duplex set up:
1. Configure your dual band HT to transmit and receive on one UHF simplex frequency with the PL tone of your mobile repeater.
2. Set up your mobile radio to receive the UHF and re-transmit on VHF with the same PL tone as set in 1 above.
3. Program the VHF side of the radio to receive on the main repeater with the proper PL tone and re-transmit to you HT via UHF.
4. Use the time-out timer on your equipment if it is available.
5. Place the mobile radio in cross-band repeat mode. Check the power levels to make sure they are at minimal levels.
6. Some mobile radios have the capability to automatically ID. Use this feature to meet FCC requirements. (NOTE: Most nets require that all completed interactions finish with your callsign which would satisfy FCC requirements.)
That concludes tonight’s training. Are there any questions, comments or suggested additions to this material?
Thanks, this is (callsign) clear to net control.
Send corrections, modifications, updates or suggestions to k5prs@aol.com