Uniden Close Call
From The RadioReference Wiki
Close Call™ RF Capture Technology
Instantly tunes to signals from nearby transmitters. A Uniden Specific feature for their scanners. Close Call can operate by itself or in the background (like priority) while scanning and/or searching.
The feature is designed to catch signals that are "Close" (hence, the name). While you might not get a hit often, it should be the case that any hit you do get is from a relatively nearby transmitter, so could be of enhanced interest to you.
The Close Call feature is also implemented on the RadioShack Pro-83, Pro-84, and Pro-2051 as "Signal Stalker". "Signal Stalker II" (used on some other RS models) is a different frequency detection method implemented on some GRE-made RS models.
For the Close Call feature to detect a signal, that signal must be about 15-18dB stronger than the RF noise floor in the band being checked. This means that there is no real way to predict the range within which signals will be caught. The factors that influence range, however are:
- RF Noise Floor in the band (lower noise floor increases range)
- RF Power Output of the Transmitter (higher power increases range)
- Antenna being used for receive (too complicated to predict, but it does have an affect :*)(by acting as a tuned system, it can pre-select within the required band. Other out of band signals will be attenuated) )
Note that "RF Noise Floor" in this context includes signals from any other transmitters operating in that band. So, at busy airports, getting a hit might be difficult (lots of VHF signal sources all the time, as well as a few continuous VHF broadcast sources).
Uniden Scanners that support Close Call include:
Close Call Do Not Disturb
When set in this mode, the scanner will periodically make Close Call checks whenever the scanner is not receiving audio in another mode. This eliminates the annoying breaks in conversation while still allowing for the Close Call functionality.
Close Call Priority
Checks for a close call signal every 2 seconds.
Close Call Temporary Store
When this option is turned on, when the scanner gets a Close Call “hit", it temporarily saves the hit and includes that frequency when scanning. The scanner keeps the last 10 hits (older hits are erased by newer ones). Hits are lost when power is cycled. You can store a hit into memory by pressing “E" when on that frequency.