26-11-2019, 03:48 PM
(This post was last modified: 26-11-2019, 03:49 PM by ppppenguin.)
By the time the Domino was designed, the ADC wasn't a problem. The TDA8708 and 8709 (it used one then, don't remember which) were good for at least 20MHz, probably 30.
As for SDR, only the most expensive ones will be doing direct synthesis for TX (or ADC for RX) at much over a few MHz. Where "a few" is not well defined but might be as low as 10MHz or as high as 50MHz. Typically they will work at IF and use up (TX) or down (RX) conversion. not really my field but they may well use quadrature conversion. Mike, as you found, many will be working at very much lower IF.
Frank Cuffe and I both did some work on DDS for Band 1. He got a decent result for 45MHz vision using a sample rate around 200MHz. DACs for this sort of speed are readily available. I think his was 14 bit. I did a rough trial at about 16MHz with about 80MHz clock. My setup (borrowed from another project) wasn't really suitable . for anything higher. It's all written up somewhere here on GVR.
As for SDR, only the most expensive ones will be doing direct synthesis for TX (or ADC for RX) at much over a few MHz. Where "a few" is not well defined but might be as low as 10MHz or as high as 50MHz. Typically they will work at IF and use up (TX) or down (RX) conversion. not really my field but they may well use quadrature conversion. Mike, as you found, many will be working at very much lower IF.
Frank Cuffe and I both did some work on DDS for Band 1. He got a decent result for 45MHz vision using a sample rate around 200MHz. DACs for this sort of speed are readily available. I think his was 14 bit. I did a rough trial at about 16MHz with about 80MHz clock. My setup (borrowed from another project) wasn't really suitable . for anything higher. It's all written up somewhere here on GVR.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
