[Elecraft] Good Low Cost Audio to USB Interfaces For Digital Modes

[Mike]

Interesting, especially the decode number. Have you an opinion on the iMic?

73, Mike NF4L

On 3/8/2012 8:59 PM, Jim Brown wrote:
> in the last few days I've been evaluating a couple of low cost audio to
> USB interfaces for use primarily with digital modes -- RTTY, PSK, JT65,
> FSK441. My primary objective is to improve decode performance at low
> signal levels. I studied the catalogs and chose two low cost units that
> looked like they would do the job and would not have RF problems.
>
> Here's a link to a little Numark adapter that I bought for $33.  t's as
> cute and easy as it looks.  Power from the computer, a couple of RCA to
> 1/8-in cables for gozinata and gozouta.
>
> http://www.bhphotovideo.com/c/product/639303-REG/Numark_STEREO|IO_Stereo_iO_USB.html
>
>
> The other one I bought is this Tascam unit.  A bit larger, more
> mechanically robust, mostly metal enclosure, more flexible with respect
> to levels.  The 1/4-in jacks for guitar and mic have more gain, so will
> work with lower signal levels.  $70
>
> http://www.bhphotovideo.com/c/product/648495-REG/Tascam_US_100_US_100_USB_2_0_Computer.html
>
>
> To evaluate them I hooked them to different Thinkpads running JT65-HF
> and fed both of them from the line of a K3, then compared their decode
> performance, and also compared them with the Thinkpads' internal sound
> card.  The two new adapters performed equally well, and often produced
> almost twice as many decodes on a given pass as the the internal cards.
> Next I transmitted through them and looked at their spectrum on a P3
> hooked up to a second K3. Distortion products look minimal on both units.
>
> I also pulled them apart and studied their construction.  Both use
> proper construction that avoids the Pin One Problems that cause RFI
> issues. Now that I'm sure that they work well, I'm rewiring my station
> to use them in place of the sound cards built into my Thinkpads for SO2R
> contesting and everyday digital operation on both HF and VHF.
>
> Both of these units are a real bargain from well known audio vendors.
> Their interface to the K3 (and other rigs) is really simple. They don't
> do any control functions, so you still need a serial or USB to serial
> for that. I use VOX to key the K3.
>
> Both are available from other vendors, but B&H had the best prices I
> found, and shipping by UPS Ground was free.
>
> 73, Jim K9YC
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