[RTTY] HAL ST-8000 and 6000 vs. Sound Cards

[Kok Chen]

On Jan 29, 2005, at 6:23 AM, psussman at pactor.com wrote:
>  Rather that TNCs are easier to set up
> because they come with instructions ....

I think I agree with Phil here.

My twist on the statement is that the reason could be because a 
software based modem can (emphasis on the word "can") be better than 
TNCs so it may be easier set up your station to max out the decoding 
capabilities of a TNC than it is to max out the decoding capabilities 
of a software modem.

> ... while software stuff requires a lot of patience or a dedicated 
> Elmer to get it right.

I don't think it is difficult to provide the tools within the modem app 
itself to aid proper set up, and be able to bypass a human Elmer.  An 
example of a good tool is actually in a hardware box -- the Timewave 
599zx.  That box has an AC millivoltmeter built right in.  You can very 
easily adjust the gain of the audio chain so that its A/D converter is 
optimally set up.   It also has a built in AFSK generator (generates 
tones, diddles, RYRY) for adjusting the transmitter.

As a couple of folks have repeatedly mentioned here in the past: if you 
are not printing at least as well with a proven good software modem 
than you can with a TNC, the likelihood is you need to look closer at 
how everything is put together at your station.

I would first make sure that the A/D converter is top notched (don't 
just look at how many bits it supports but look for the actual noise 
floor numbers, whether it supports balanced inputs, etc etc -- the 
stuff the professional recording world looks for), with gains in the 
audio chain adjusted for maximum dynamic range and never clipping 
(RITTY has always bragged about the use of a non-limiting front end, 
for what I believe are solid reasons), and with as much hum/noise 
removed as possible.  In most cases, with the basics done properly, you 
can do as well or better than a TNC using just a good "textbook" 
software modem with no special tweaks.

73
Chen, W7AY