Hear Clear and weak signal strength.

[Vinnie]

Can anyone offer their experiences with Hear Clear…

How does Hear Clear work with non Hear Clear radios operating point to point and through repeaters operating with and without Hear Clear…

Can Hear Clear be used in a trunking system and applied to specific talk groups…

Finally, how does Hear Clear affect a radio’s battery life…

[thebigphish]

Hear Clear is essentially "companding" with a newer & cooler name, in which the radios compress the audio spectrum slightly on transmit, and then expand is slightly on recieving it...in efforts to improve the audio clarity.

(don't know if i'll get in trouble for quoting another site, but here it goes - its' the best description of this i could find - short of racking my brain for the words)

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.

or browse thru the page yourself @ Repeater-Builder.com page on GTX radios

[nmfire10]

Yep. That is basicly it. When it is used on the all the radios, it is definately an improvement. We use it on our 900 system here and it really does take the noise floor right down. It's all voice and no hissing or popping. I've been tossing around the idea of enabling it on our FD's narrowband repeater system (kenwood).

[chiefhal3]

I have a VHF XTS5000 and when I am programming it I notice that I can select the hear clear option. Just curious if since it is allowing me to select it, is it working on VHF? The audio of the XTS5000 is much better than that of our XTS3000's or MTS2000's. This is a conventional system by the way if that matters.

[nmfire10]

You need ALL the radios on the system including the base infrastructure to support hear clear and have it enabled. Do not turn it on by itself, it will make things worse.

[xmo]

"Hear Clear is essentially "companding" with a newer & cooler name..."
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There is a reason for that different name and the reason is that "Hear Clear" is more than simple companding. Motorola does offer simple companding, for example in the PRO-series radios. The CPS calls it companding and the help file explains how it works.

Hear Clear was introduced by Motorola specifically for the 900 band.

Hearclear is a combination of two techniques to improve audio quality by both compensating for the narrow channel bandwidth and by decreasing the effects of Rayleigh fading.

The narrow channel bandwidth is compensated by companding which lowers the noise floor and expands dynamic range by 1:2 on a logorithmic scale. That's the basic technique that others offer and that Motorola offers on other frequency bands.

The other problem that Hear Clear deals with is Rayleigh fading which causes rapid drops in signal strength. It is the Rayleigh fading that causes all the clicks and pops while in motion. This effect is more pronounced at higher frequencies such as 900 MHz due to the shorter wavelength.

The second part of Hearclear - "Flutter Fighter" - uses RSSI under microprocessor control to dynamically reduce receive gain during fades to minimize the audible effect of the noise bursts.

Bench testing doesn't show off the Flutter Fighter part of Hearclear [unless you have a BIG $ Rayleigh fading simulator] - so if you really want to evaluate it - you should try it in the field.

Other brands of radios have simple companding but not Flutter-Fighter, so even though they may be 'compatible', the Motorola technology may sound better.

[nmfire10]

I can attest to cross-manufactuer incompatibility. It doesn't work.