[amsat-bb] Re: DSP Speaker

n3wwn@futuretek.cx n3wwn at futuretek.cx
Thu Apr 12 11:35:00 PDT 2007

Hi Tony, Roger and Bob!

The "winning" unit is an Am-Com ClearSpeech Base Unit.  It goes inline 
between the audio output of the rig and the external speaker.  This was 
based on the reviews on eHam.net ( http://www.eham.net/reviews/detail/1041 
) as well as Jeff's asking price.

No settings, just an on/bypass type toggle switch.

Not being familiar with other DSP units, besides my old Radio Shack DSP 40
http://www.eham.net/reviews/detail/4630 , I was pleasantly surprised by 
the amount of white noise reduction and astonished by the amount of steady 
tone elimination that the ClearSpeech unit offers!

The DSP 40 can handle the steady tone elimination somewhat, but the white
noise reduction was very poor.

The ClearSpeech Base unit was tested last night on 6m with a semi-local 
ham (same grid square but about 30 miles away), K3JRD.  The noise floor 
was around S7-S8 and Jim's signal was a S9+, but there was still a lot of 
white noise in the audio.

I'm actually ahead of myself here... I wanted to test the DSP unit without 
being "at the radio", so I fired up my 6m rig and tuned to 50.125 USB. 
With the DSP off, I had the usual loud white noise.  With the DSP on, the 
white noise dropped remarkably.  Much to my surprise, about 30 minutes 
later, I heard K3JRD calling... it was MUCH louder than the white noise, 
showing how much attenuation was being done.

During the QSO, I disabled and re-enabled the DSP several times to see the 
difference.  It's night and day with my Kenwood TS-660 which has no 
built-in DSP (not even a notch filter)!

When I get chance I'm going to check out DttSP software that Bob 

Sorry if this is off topic since I haven't had chance to use it on a 
satellite yet... give me a chance! hi hi

73 de Rich N3WWN

On Thu, 12 Apr 2007, Tony Langdon wrote:

> At 12:04 PM 4/12/2007, Roger Kolakowski wrote:
>> And the winning answer was....?
> That one's got me curious too.  I'm particularly fussy about DSP noise 
> reduction, and there are very few that I actually like.  The one I use is 
> made by Michels Engineering in Germany, which provides an excellent degree of 
> noise reduction and doesn't distort the audio as severely as many others. 
> For me, that distortion interferes with my ability to pull a signal out of 
> the mud, and most of the DSP noise reductions work best for me in the "off" 
> position, as far as readability goes.  The Michaels one, OTOH, has no impact 
> on readability at worst, and often a modest improvement, as well as excellent 
> noise reduction.  On very weak FM signals (ideal for SO-50 
> :) ) , the readability is dramatically improved, and the DSP can 
> almost act as an FM voice activated mute.
> 73 de VK3JED
> http://vkradio.com

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