Seems we are reaching the age of the "crippled PC". For a desktop there should still be a chance of adding a serial port PCI card. I have never used the parport for PTT so far, and it seems I never will...
USB is adequate for most common PC jobs, but not for interfacing radios without some _special_ interface. And of course, managing RTS seems to be the most adequate way of applying PTT to a radio. All other ways (VOX, CAT, etc) seem to introduce too much latency in an ARQ link. VOX may be OK just for keyboarding, which may be the the solution for most users, but hardly is a "one size fits all" solution. 73, Jose, CO2JA --- expeditionradio wrote: >> Peter OZ1PIF/5Q2M wrote: >> Either you have to add an external USB-> RS232 >> [...] or resort to the VOX solution. > > Hi Peter, > > For ARQ or handshaking modes, VOX is simply > way too slow. Signalink will not work. > Not an option. Let's crunch the numbers: > > 1. Really fast VOX with 25milliSecond PTT delay. > 2. Add 12mSec to 30mSec transmitter 90% power ramp-up. > 3. Total delay = 37mSec to 55mSec! > > Now, let's take a typical example of a slow ARQ > or handshaking mode running at 125 baud (symbols/second) > It transmits one symbol every 8 milliseconds. > In 37mSec, you have missed 4 symbols. > In 55mSec, you have missed 7 symbols. > > Each time you miss some symbols, this creates > more errors that need to be corrected somehow. > So, each transmission with a VOX system, you > create errors... and each ARQ transmission is > trying to fix the previous transmission's error, > and the previous errors in the transmissions before > that... a vicious cycle :) > > The other issue is VOX release delay. The longer > it is, the more the receive decoder will miss > symbols. > > VOX is totally wrong for ARQ modes. > I'm surprised that Signalink doesn't offer > any RTS keying, it would be so easy to add > to their interface. They are really shooting > themselves in the foot with their design choice. > A lot of hams are buying these Signalink and > other VOX interfaces, and they don't realize > what they are missing by doing so. Of course, > Signalink doesn't tell them, (the truth would > be bad for business). > > 73 Bonnie VR2/KQ6XA
