Don, After making several sound-card interfaces (never have used a commercially made one), I deduced the "surest way" to avoid audio problems was by total isolation of computer ground and radio ground. East to accomplish using isolation transformers for audio and opto-isolators for dc controls.
I guess there are applications for a "VOX-like" PTT control, but I use RTL or DTR lines for this with the sw I run. Opto-isolator like the 4N36 work well in this path. I am going to go ahead making up an I/F with tiny pcb transformers, but probably not try installing all inside a sub-D connector (commonly called DB-9 or DB-25). I will use a tiny plastic box and small pc board with mini-phone connectors for audio and DB-9 for RS-232 interface. I have in mind that it will attach on the back of the KX3 with a velcro-patch (so one can remove it at will). I am just stacked up at present so this will not be worked on right-away (assuming Lance has one for his eme dxpedition). I am writing a power-point presentation to demo the KX3 this weekend. I'll add it to my website afterward. 73, Ed - KL7UW At 02:49 PM 7/12/2012, Don Wilhelm wrote: >Thanks, yes that is the one that produces the PTT from the audio stream. >I note that Skip no longer has kits and boards, but he has supplied >a complete parts list and the circuit is simple enough to wire on >perfboard. The photos provide a nice layout guide. > >Contrary to K9YC's statements, I believe the transformers are >necessary for use with a laptop. >Jim's "bond everything together" is a great solution (and it works) >for the home station using a desktop computer, but bonding the >computer becomes more difficult when using laptops with all plastic >cases. I cannot find a good place to connect to the computer ground >of my IBM Thinkpad.unless it just happens to be the jackscrews on >the VGA connector - but those are there to prevent connector >pullout, and may or may not be grounded. (I use a desktop at the >home station). > >73, >Don W3FPR 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 50-1.1kw?, 144-1.4kw, 432-QRT, 1296-?, 3400-? DUBUS Magazine USA Rep [email protected] "Kits made by KL7UW" http://www.kl7uw.com/kits.htm ====================================== ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
