[App_rpt-users] Figured it out!

Jim W7RY w7ry at centurytel.net
Sat Jul 27 20:43:35 EDT 2013

Here is a cut and paste from Repeater Builder:

Hear-Clear is a noise reduction system trademarked by Motorola. It's probably similar to other manufacturer's compression/expansion techniques. Spectra radios call it a compander. The system looks at the received signal strength and the high frequency noise at the receiver and adjusts the audio response to eliminate most of the flutter, pops, and clicks that are prevalent with motion. The transmitter audio is filtered and compressed to bring low levels up. The receiver applies similar expansion to return the audio to normal levels. This also tends to reduce the high frequency components and a lot of the noise along with it. The audio filtering tends to make the audio sound thin, but most of the energy is now in the normal communications-quality frequency range of about 400 to 2500 Hz. PL and DPL are unaffected.

In an all-Motorola repeater environment, Hear-Clear would be enabled on all user radios as well as the repeater. The repeater's receiver will adjust its action based on the signals it hears. The user's radio will adjust its action based on the signal put out by the repeater. Unfortunately, Hear-Clear is only available on 900 MHz products. In MaxTracs, the Hear-Clear component (one IC) is mounted on the microphone jack circuit board and the 900 MHz logic board enables or disables the circuit on a channel-by-channel basis (configured through RSS). Hear-Clear is either enabled or disabled, and it always affects both receive and transmit audio.

A repeater without Hear-Clear can still be used. The repeater must pass clean audio and the user radios can have Hear-Clear enabled. Unfortunately, the part of the system that utilizes signal strength will be fooled by the constant strong signal coming from the repeater's transmitter, but the user radios will still benefit from the compression and expansion of the audio signal. Pops and clicks will be noticeably removed. Radios without Hear-Clear can also use the repeater, but the audio will sound strange if a mix of radios is used.

-----Original Message----- 
From: Jim W7RY 
Sent: Saturday, July 27, 2013 5:20 PM 
To: Mike Wolthuis ; app_rpt-users at ohnosec.org 
Subject: Re: [App_rpt-users] Figured it out! 

Not really... You really don’t want to enable hear clear. Hear clear is 
really for narrow band. For Motorola microphone circuit, you need to use the 
additional amplifier on the URI. What interface are you using?

Jim W7RY

-----Original Message----- 
From: Mike Wolthuis
Sent: Saturday, July 27, 2013 3:23 PM
To: app_rpt-users at ohnosec.org
Subject: [App_rpt-users] Figured it out!

Hear clear needs to be enabled to get enough audio.

Thanks all,

Sent from my iPhone
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