On Sun,6/18/2017 5:20 PM, Joe Subich, W4TV wrote:
Using the Icom controls is far more reliable than using a "Y" connection on a RS-232 connection; it avoids issues with loading RS-232 circuits and the isolated CI-V Transceive emulation provided by the microHAM interface avoids issues with collisions/corrupted commands on a shared CI-V bus.
I know you know this, but others might not -- RS232 is NOT a matched system. It uses a low-Z driver and a high-Z receiver. The real issue with loading is CAPACITANCE -- later versions of the RS-232 Standard reference cable capacitance and baud rate rather than cable length as the limit of transmission distance. CAT5/6/7 cables are among the lowest capacitance paired cables we can easily buy, and their loss is fairly low at RF. CAT5/6/7 cables are four twisted pairs, each with a different twist ratio to minimize crosstalk. RS-232 cables wired to use one of these pairs for each of the signalling circuits are about as good as it gets without spending big bucks. Most ham gear uses only RXD and TXD (pins 2 and 3 on a DB9) with pin 5 as return.
My serial cables use two pairs to connect 2 and 3 with both pairs returned pin 5, and with the remaining conductors wired to the DB9 shells. My cables are pretty short, but I've used cables like this that are 200 ft long or longer to connect a computer to sound system DSP to do system setups at fairly high baud rates.
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
