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G8MNY  > DSP      27.11.02 15:55l 57 Lines 2217 Bytes #-5842 (0) @ WW
BID : 28011_GB7CIP
Subj: Noise Eliminating Loudspeaker
Sent: 021127/1435Z @:GB7CIP.#32.GBR.EU #:28011 [Caterham] $:28011_GB7CIP
To  : DSP@WW

Hi All,
     I recently bought a BHI NES 10-2 after reading the December Radcom Article
by G4HCL, and hearing actually demonstrated at a rally. The demo is what really
sold it to me.

Quite amazing performance, don't be fooled by the little loudspeaker box, it
really is the state of the art Digital Signal Processing noise reduction unit.

It has 8 levels of noise reduction set up on a not very friendly DIL switch on
the rear as well as an I/P volume control & noise reduction on/off switch that
also lights a red/green LED. The unit is power by the usual 2.1mm DC connector
(+ in the middle) & seems to have an idiot diode for basic protection. 

Here are some performance figures I measured from my one...


      DIL          SSB        1KHz 
    SETTING       NOISE *     TONE

     1 Min        9 dB       4 dB
     2           11 dB       5 dB
     3           12 dB       6 dB
     4           13 dB       8 dB
     5           16 dB      16 dB
     6           19 dB      21 dB 
     7           24 dB      25 dB
     8 Max       33 dB      65 dB

* Noise & Tones was measured on a flat average analogue meter. 

At 8 MAě therň iˇ n´ neeń t´ usň ▀ SQUELC╚ oţ FMČ in fact ▀ choppinš squelcŔ iˇ
unhelpfully aˇ thň retraininš noisň DSđ jumps the noise on & off. The only
problem is knowing when an over has occurred as you are left with almost
silence, just the DSP remnance musical tones at -33dB.

FREQUENCY RESPONSE (external connections) 25Hz - 4.5KHz @ -3dB.
         which makes it quite acceptable for Broadcast signals.

TIME DELAY was 27mS, which I guess is the time to go from Analogue to Digital
& back to Analogue.

In off mode the audio still goes A-D-A but without any noise processing, you
still ge˘ thň frequenc¨ filterinš duň t´ thň 12KH˙ samplň rateČ eš ▀ 6KH˙ 
turnove˛ frequency & filtering that gives -3dB @ 4.5KHz.

IN USE, I found that you soon get used to the musical artifacts (like digital
cellphones) that the highest level of DSP give you, as these are much preferred
to normal very noisy comms audio. At moderate level, moderate noise reduction
occurs & the recovered 

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