Tutorials

The Complete Uniden SDS100 Close Call Tutorial

A Beginner-Friendly Step-by-Step Guide to finding nearby signals.

What Is Close Call? (Understanding the Basics)

Before we dive into how to use it, let's understand what Close Call actually does. Think of Close Call as a "signal hunter" feature built into your SDS100 scanner.

Here's the simple explanation: Close Call automatically searches for strong radio signals from nearby transmitters and alerts you when it finds one. It's designed to catch transmissions that are happening near you—signals that are strong enough to get past all the radio "noise" in the air.

For example, if a police officer with a strong transmitter is broadcasting 2 miles away from you, or a helicopter overhead is transmitting, Close Call can detect it and show you what frequency they're using. This is useful when you hear something interesting but don't know what frequency it's on, or when you want to discover what's happening in your immediate area.

Important technical detail: For Close Call to detect a signal, that signal needs to be noticeably stronger than the background radio "noise" in the frequency range being checked—about 15 to 18 decibels (dB) stronger. This is why range varies and isn't guaranteed. A strong, nearby transmitter will definitely get picked up. A weak, distant one might not.

The Three Close Call Modes (What Each One Does)

Your SDS100 has three different ways to run Close Call. Each one behaves differently, and choosing the right mode depends on what you're trying to do.

Mode 1: Priority

What it does: The scanner checks for Close Call hits every 2 seconds, and when a strong signal is found, it takes priority over whatever you're currently listening to. In other words, a Close Call hit will interrupt your scanning to show you the new frequency.

When to use it: Use this when you want to catch nearby signals more aggressively and don't mind being interrupted. This is great when you're specifically hunting for unknown frequencies in your area.

Trade-off: You might miss parts of conversations on your regular scan list because Close Call keeps interrupting.

Mode 2: Do Not Disturb (DND)

What it does: The scanner still checks for Close Call signals periodically, but it's polite about it. It only checks for Close Call hits during gaps between transmissions on your regular scan. It won't interrupt an active conversation.

When to use it: Use this when you want the benefits of Close Call without losing continuity of conversations you're monitoring. This is the most popular mode for casual scanning.

Trade-off: You might miss some Close Call hits if there aren't enough quiet gaps for the scanner to check.

Mode 3: Off

What it does: Close Call is disabled completely. The scanner ignores all Close Call scanning and just does regular scanning.

When to use it: Use this when you want to focus on your regular scan lists without any Close Call activity.

How to Turn On Close Call (The Quick Method)

This is the fastest way to activate Close Call if you're already scanning normally.

Locate the Function Button: Look at the left side of your SDS100. You'll see a green button labeled "FUNC" (Function). This is your key to quick access.
Press and Hold the Function Button: Press the green Function button on the left side of the scanner. Hold it for about 3 seconds until something appears on the display at the bottom of the screen. You might see a timeout indicator—don't worry, this is normal. You'll see menu options appear at the bottom of the display.
Look for "Close Call" on Screen: On the bottom of your display, you'll see several options. One of them will say "Close Call". Look for it—it's usually one of the options that appears.
Press the Button Below the "Close Call" Text: At the bottom of the SDS100 display, there are buttons that correspond to the text above them. Press the physical button that's directly below where it says "Close Call" on the screen.
Cycle Through the Modes: Once you press the Close Call button, the mode will start cycling through automatically. You'll see the mode change on the display as it cycles: DND (Do Not Disturb), Priority, Off. Watch the display carefully. When you see the mode you want displayed, release the button and let go. Whichever mode is showing when you release the button is the one that will stay active.
Confirm It's Working: Once you've set your desired mode, the scanner should return to normal scanning view. Look at the top of the display—you should see a small "CC" indicator icon appear somewhere near the top. This tells you Close Call is now active. The icon might be different colors depending on which mode you chose.

Timing tip: This cycles FAST, so you need to be quick. If you miss the mode you want, just press the Function button again to go through the cycle again.

How to Turn On Close Call (The Menu Method)

If you prefer using the menu system, or if the quick method seems confusing, here's the menu-based approach that gives you more control.

Press the Menu Button: Look at the bottom of your SDS100. You'll see a red button labeled "MENU". Press it once.
Scroll Down to Find "Close Call": You'll see a list of menu options on the screen. Use the volume knob (the big dial on top of the scanner) to scroll down through the menu options. You're looking for an option that says "Close Call" or "Srch/CloCall Opt" (short for Search/Close Call Options).
Select It: Press the volume knob straight down (or press "E/YES").
Select "Set CC Mode": After selecting Close Call, you'll see another submenu with options. Scroll to "Set CC Mode" and select it.
Choose Your Mode: You'll see these options:
- Off
- DND (Do Not Disturb)
- Priority
Use the volume knob to scroll to the mode you want and press down to select it.
Exit the Menu: Press the Menu button again to exit and return to normal scanning view.
Look for the CC Icon: Just like with the quick method, look for a small "CC" indicator on the top of your display. This confirms Close Call is active.

What Happens When Close Call Finds a Signal?

Now that you understand how to turn it on, here's what to expect when Close Call does its job.

You'll See:

A frequency appears on your display: The frequency that was detected will show up.
A graphical display: You might see a small signal strength graph pop up, showing you how strong the signal is.
A "Close Call Hit" notification: Depending on your display settings, you might see text indicating a Close Call hit was found.

How to Interact with the Hit:

If using Priority mode: The scanner will automatically tune to the detected frequency, and you'll hear any ongoing transmission on that frequency.
If using DND mode: The frequency will appear on your display, and the scanner will show it to you when there's a gap in your regular scanning.

Temporary Storage of Hits:

Your scanner automatically saves the last 10 Close Call hits in temporary memory. These hits disappear when you turn off the scanner. Think of it like a recently found channels list.

How to View and Save Your Close Call Hits

Viewing Your Temporary Close Call Hits:

Press the Menu button (red button at bottom).
Scroll down to "Srch/CloCall Opt" (using the volume knob).
Press down on the volume knob to enter to this menu.
Look for "Review CC Hits" or similar option and select it.
You should now see a list of frequencies the scanner found. You can scroll through this list using the volume knob.

Permanently Saving a Close Call Hit to Your Favorites:

If you find a Close Call hit that you want to keep and monitor regularly, you can save it permanently:

Scroll to the frequency you want to save in your Close Call hits list.
Press the "Enter" button (or the selection button, depending on your display).
The frequency will be saved to your Quick Favorites list. Now that frequency will be part of your regular scanning and won't disappear when you turn off the scanner.

Tips for Getting Better Close Call Results

Your Close Call results depend on several factors. Here are practical tips to improve your success rate:

Use a Quality Antenna: The stock antenna that comes with your SDS100 works okay, but a better antenna makes a huge difference. An external BNC antenna designed for 800 MHz or UHF frequencies will significantly improve your Close Call range and hit rate.
Find High Ground: Elevation matters a lot. If you can use your SDS100 at a higher location (a hilltop, rooftop, or even upstairs in your house), you'll get better results.
Hold the Scanner Correctly: Don't block the antenna with your hands. Hold it naturally away from your body, and keep the antenna pointed upward.
Get Away from Interference: Keep your scanner away from electronic devices like computers, microwave ovens, or power lines that generate radio interference.
Use DND Mode: Most scanner enthusiasts use Do Not Disturb mode most of the time. It gives you Close Call benefits without the constant interruptions of Priority mode.

Troubleshooting: When Close Call Isn't Working

No hits found?

Check that Close Call is ON (not "Off"). Try an external antenna or move to higher ground. Be patient—it depends on active nearby transmitters.

Same frequency repeats?

This is normal for active transmitters. You can avoid them through the menu if they become annoying.

Not hearing hits (Priority)?

Check your volume and squelch settings. Lower the squelch if needed.

Stopped finding hits?

Radio traffic fluctuates. Quiet periods are normal.

Quick Reference Card

Quick Start

Press green FUNC button for 3 sec
Press button below "Close Call"
Cycle to desired mode
Release to set

Modes

Priority: Aggressive, interrupts
DND: Polite, checks gaps
Off: Disabled

Final Thoughts: Close Call is one of the most fun features on the SDS100 because it lets you discover what's happening around you in real-time. Good luck with your SDS100, and happy scanning!