RadioBanter - View Single Post

July 1st 05, 11:55 PM

wrote:
John Smith wrote:

Dee:

The only person talking 300 baud is you,

No.

The FCC says so too.

I told you to throw away that
300 baud modem and get a decent one (or revamp an old phone
modem to your needs.)

On most of the HF/MF amateur bands, amateurs in the USA are limited to
300 baud for the transmission of "data".

Now it might be argued that sending .jpgs is an "image" mode, and is
only allowed in the 'phone subbands, with correspondingly wider
bandwidths. But there's more to it than just hooking a typical computer
modem to an SSB rig.

Let's say some hams find a way to fit, say, 14 kbaud into an SSB
bandwidth with characteristics that will work on the HF ham bands. And
suppose they get FCC to say it's OK and all that. The transmission of a
1 meg .jpg will still take more than a minute with no errorchecking.

Without error checking the resultant picture will almost certainly
*not* be a picture.

The "fuzziness" of analog signals is a big part of why they work at HF.
A bit of static or other noise might put some white spots or even a line
or two of noise on the SSTV screen, but they can wreck a digital
transmission without error checking.

Since you didn't even understand that, you certainly won't grasp the
rest...

Try grasping the current regulations, John....

So much more than regulations that need grasped. I await the technical
aspects of the digital image transmission system.

- Mike KB3EIA -