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downlink_tone [2019/03/09 16:26]
downlink_tone [2019/03/09 16:37] (current)
KD6KPC [Why Program a Downlink Tone]
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 ==== Why Program a Downlink Tone ==== ==== Why Program a Downlink Tone ====
 +If a repeater has an uplink tone, you must enter it to access the repeater. But, if you don't program a downlink tone (often called a decode tone) into your radio, you can still hear the repeater uninhibited. In fact, many repeaters do not transmit a downlink tone. So why bother to program one in if you can hear the repeater without it? 
 +The reason why is because you can hear //​everything else//, too. 
 +Especially in urban areas, if a lot of RF noise is generated. This elevated noise can produce signals with enough strength to deactivate the squelch on your radio. So, you elevate the squelch threshold, which works until you are in the fringe areas of the repeater and you need to lower the squelch threshold. Sometimes, the RF noise can come in full scale. These "​birdies"​ can sound like analog paging towers and can be caused by mixing with the intermediate frequency of your receiver. These birdies do not transmit a CTCSS tone.
 +When you program a downlink tone, you ensure that the only signal that can break the squelch on your radio is a signal that is carrying that tone. RF noise and birdies won't be carrying the tone. It will also filter out distant repeaters on the same frequency, as long as they are not transmitting the same tone. Think of it as preventing interference from activating the speaker on your radio. Added bonus, especially when scanning, you will have a quieter radio and won't have to bump the up/down key so often to get it to release on a noisy channel. And. many repeaters do not transmit the CTCSS tone when the repeater is identifying. ​
 +Refer to the Repeaterbook database to see if the repeater is transmitting a downlink tone. If you set your radio to encode and decode tones when no downlink tone is being transmitted,​ you will not hear audio from the repeater at all.
 ==== CTCSS (Continuous Tone-Coded Squelch System) Codes ==== ==== CTCSS (Continuous Tone-Coded Squelch System) Codes ====
 All tones are in Hz. All tones are in Hz.
  • downlink_tone.txt
  • Last modified: 2019/03/09 16:37
  • by KD6KPC