On 7/5/2017 12:23 AM, Richard Lamont wrote:
Thank you for your rigorous, quantified mathematical proof.
Good engineering is not about math proofs, it's about big picture analysis of entire systems, understanding the limitations of each element, and concentrating on those elements that optimize the entire system.
Clearly the JT65 transmitted harmonics I've seen, as received on my K3S, which blotted out the weak JT9 station I was trying to work at around -27, must have been a figment of my imagination.
I'm not suggesting that wasn't real, but simply that harmonic distortion at AF is not the only cause of the problem. And questioning that shifting the TX signal to a frequency where the harmonic is out of the audio passband is the only solution.
Using a better audio interface and setting levels correctly can easily get individual AF distortion products 60 dB below the the level of sine wave modulation. In an earlier post, I noted that interfaces sold to semi-pro audio users generally offer THD in the range of 0.5 - 0.1% and that number is the root-sum-square combination of the individual components. In that earlier post, I included a link that suggested specific make/models suitable for this use, all below $100 US, and four easy ways for users to set levels, depending on the available tools (including ears).
You also seem to have missed my objection that WSJT-X forces the radio into split mode, when I want to use the second RX (controlled by the 2nd VFO) to SIMULTANEOUSLY monitor CW while I'm in RX mode with WSJT-X, AND to quickly do and A/B exchange of VFOs to work a station I hear on CW, then return to WSJT-X. I did that almost continuously during the big opening we experienced here last Friday, and one of those times got me a new grid (in a new state) 2,500 miles away.
There's another powerful way to prevent overload of your RX by your neighbor -- out here in W6, neighbors try to TX on the same cycle as our neighbors. No math proofs required.
73, Jim K9YC ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
