external sound cards and multi decodes
I have been getting several instances of multi decodes, the central signal being strong with 100Hz images. Reading posts here suggests that it may be due to a harmonic as such created in a sound card, although I have not noticed anything untoward with other audio decodes on other applications such as DM780.
A particular issue was mentioned as regards the card specifications (V2 limiter or something like that... sorry), however a search on tinternet fails to provide me with any leads on suitable units.
Can anybody here suggest a unit available in the UK which would suffice? Have no space in the machine for another internal card so must be external.
- On 7/23/2013 11:39 AM, chas cartmel wrote:
Can anybody here suggest a unit available in the UK which would suffice?
A few years ago, I studied the range of USB sound cards designed for the home studio market and bought two that I tested extensively with JT65-HF. They are the low cost Numark stereo unit (about $35 from B&H in NYC) and a simple Tascam stereo (don't recall model number, it's been discontinued and replaced by one with more inputs). Paid about $75 from B&H. The replacement is around $100 or so.
Both units perform quite well, regularly giving me six or more decodes in a single pass, and often in the range of -20 to -22 dB. That's roughly twice as many decodes as from the sound card built into my Thinkpad, and set up with both looking at the same signals. I rarely saw decodes from the internal card below -13 dB. For the tests, I used two different laptops, one using the built-in card and the other using the USB card. For obvious reasons, I no longer use the internal sound cards. :)
For RTTY contesting, I run SO2R with the Numark on one radio and the Tascam on the other. I've never seen any evidence of multiple traces produced by distortion in the sound cards. Both sound cards also improve decoding as compared to the internal sound card.
I suspect that Tascam is distributed in the UK. Don't know about Numark -- they're a smaller company, with products generally targeted to nightclub DJ applications.
73, Jim K9YC