I ran a few tests to see just how long it really takes for sending a document via a digital data program such as WinDRM. If you had a good path and probably at least a 10 db S/N ratio, the transmission time for my test document of 29 K was only about two minutes. The test file is a two page document with an inserted table listing the Emission Classifications and then some additional notes. Fonts are large so a close spaced two page doc might be large in size. However, 20 to 30 K is very doable on digital SSTV so docs should be no different.
Now if you convert this .doc file into a moderately compressed (90%) pdf file, it grows to 67 K, so that is probably not a good direction. A possible answer might be to move toward the coming standardized file structure already available in FOSS software such as Open Office that uses the Open Document formats such as Open Document Text (.odt). These files are almost always half or less of a MS .doc file and yet it seems to have quite adequate formatting and Rich Text equivalency. The identical ODT file was transmitted in about one minute. Needless to say, this is really pretty neat since the program can ask for any fills if there are damaged blocks, a crude form of delayed ARQ. And in between you can be chatting back and forth on voice too. This has major applications for emergency type communications, especially with the need to send ICS Form 213 and that type of document. For really bad conditions, you could not use voice all that easily anyway and would want to revert to the Data/RTTY part of the band to send it as text perhaps, but that is not that easy to do with tabular information. Perhaps we should be carving out a frequency for playing with this digital stuff in the HF bands? At one time wasn't image only available to Advanced and Extra Class here in the U.S. and that was what lead to the choice of frequencies? If I understand it correctly, General Class Operators can use image anyplace on their voice privelege areas under the current rules. Perhaps we could use 5 KHz above the bottom of the General Class voice frequencies. That way if you did use LSB you would not be accidentally out of your subband if you were a General. Since 7175 will be the new lower end of the band for 40 meters, maybe we could use 7180. Then on 80 meters for "local" work, we could use 3810. And on 20 meters, which won't change, we could use 14220. If there are existing nets we would have to work around that of course. 73, Rick, KV9U John B. Stephensen wrote: >The FCC rules provide the following definitions for fax: > > Image. Facsimile and television emissions having designators with > A, C, D, F, G, H, J or R as the first symbol; 1, 2 or 3 as the second > symbol; C or F as the third symbol; and emissions having B as the > first symbol; 7, 8 or 9 as the second symbol; W as the third symbol. > > Facsimile. A form of telegraphy for the transmission of fixed images, > with or without half-tones, with a view to their reproduction in a > permanent form. (RR) > > Telegraphy. A form of telecommunication in which the transmitted > information is intended to be recorded on arrival as a graphic > document; the transmitted information may sometimes be presented > in an alternative form or may be stored for subsequent use. (CS) > >Since it can be transmitted in either analog or digital form with almost >any kind of modulation and there are no encoding restrictions, a fax >seems to be any printable document -- even if it isn't printed immediately. > >73, > >John >KD6OZH > > >
