I am sorry, but I must disagree with both Jim and Ray on this issue. Current computer audio interfaces are a fine way to introduce hams to digital modes and the only way to connect to an analog radio, but they are not the way to go for best-of-breed digital mode operation. As with CW and SSB, it would be good to get as much dynamic range as possible so the computer waterfall can be used to scan for weak signals even when there are strong signals nearby. Any distortion added by the interface only makes decoding harder, and is not desirable for best-of-breed performance.
The issue of format of the digital data seems simple. For maximum compatibility, the interface should emulate an USB sound card. (For example, the popular Signalink USB also emulates a USB sound card and is compatible with most computer software.) The K3 uses a 24 bit D/A converter for audio, and there are 24 bit USB sound cards, so 24 bits seems to be the minimum level of support. The K3 DSP is 32 bit floating point, so more bits could be used if enough computer software support them. There may be an issue with sample rate differences between the DSP and what USB sound cards support, but it should be possible to deal with that issue in the interface. If there is important software that only works with 16 bit and not with 24 or greater bit sound cards, then it may be necessary to have a configuration option, but it would reduce dynamic range, which is one of the most important benefits of a direct interface. I admit I have not paid too much attention to the internal K3 decoders, but in my brief try I had difficulty decoding weak PSK31 signals. I might be able to improve with more practice, but there are some features available with my computer software, cocoaModem, I have grown to like that aren't available on the K3: 0.1 Hz tuning increment Automatic record of an entire rag-chew QSO for summarizing in the logbook. More digital modes. E.g. my only Puerto Rico QSO is on PSK63. [Sorry I don't have USB sound card references. I'm processing email offline.] Cheers - Bill, AE6JV On 4/20/12 at 10:09, j...@audiosystemsgroup.com (Jim Brown) wrote: >On 4/20/2012 9:36 AM, Bill Frantz wrote: >>With a K3, the audio starts in digital form in the DSP. >>Converting it to analog to convert it back to digital for input >>to the computer can only introduce distortion. >> >>I'm lobbying Elecraft for a direct digital interface. > >Yes, but -- there is the issue of the FORMAT of the digital >data, both from the points of view of encoding and of physical >interface, which are likely to be quite different within the >radio and the computer, and the two systems must be able to >talk to each other. Given that there are many low cost A/D -- >D/A converter/interfaces on the market that work fine, that's a >wheel that Elecraft does not need to invent. > >73, Jim K9YC On 4/20/12 at 11:02, raysil...@verizon.net (Ray Sills) wrote: >Plus... if the audio levels are properly set, the distortion >levels should be very low. Certainly, the distortions of the >RF signal due to propagation would be worse than the >conversion distortions. >If you use the on-board method of sending RTTY or PSK31, you >would get the benefit of not having to convert analog audio to >digital, etc. > >73 de Ray >K2ULR ----------------------------------------------------------------------- Bill Frantz | I like the farmers' market | Periwinkle (408)356-8506 | because I can get fruits and | 16345 Englewood Ave www.pwpconsult.com | vegetables without stickers. | Los Gatos, CA 95032 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
