How www.slowscantv.com works...
We start out with the shack. It's very simple, we have an Astron RS-35M power supply for our Icom IC-746 Pro,
which uses a 160 Meter Loop Skywire at about 30 feet. The audio out and microphone connection from the 746 are run
into a homebrew interface. The interface is also connected to a homebrew audio mixer that allows us to route
the audio from 4 sources to either of two outputs, one being a set of amplified speakers and the other the
audio input of the soundcard in a computer that is running Ubuntu 8.04 (Hardy Heron) This is the first Linux
machine we have ever had, but our servers are running, or have run, FreeBSD and Solaris,
so we are fairly familiar with Unixes. The Ubuntu computer was running WindowsXP up until February 27th of 2008,
at which time we decided to try a GUI on a Linux machine. But, I digress...
We are currently running QSTTV version 5.3 and MMSSTV under Wine.
The SSTV software saves the images as bmp's to a directory on the Ubuntu machine and our software checks that directory every
15 seconds to see if any new images are present. If it finds a new image, our software checks to make sure it is
a valid image (i.e. it isn't half a picture with the other half being solid blue in color, etc. This is how QSSTV saves
the images if it loses sync, resyncs, or if the SSTV signal fades.) If the image is determined to be valid, our
software adds a time stamp to the bottom of the image that is shown on the website as the latest image. The actual
image that is displayed when you visit our website does not include the timestamp, that is only used as the main
image that is shown on the SSTV web cam pages at different locations on the Internet. Our software is written in
Perl and we use ImageMagick to add the timestamp and convert the files from bmp's to jpg's. The timestamp includes
the date and time that image was created, and when we are running QSSTV, the mode that was used to transmit the image.
This is one advantage QSSTV has over MMSTV, you can determine the mode from the filename. The original file is
converted and sent to the sstv directory on the web server. The software keeps track of all the images using a
flat-file database, and when an image is more than 64 hours (or whatever we set the retention_time to) old the
image data is removed from the database and the image is deleted from the server. This allows visitors to view
all the images received within the last 64 hours. If no image is received for an hour, an image is displayed
to indicate this. Generally that happens when band conditions aren't great. During the day the 746 is tuned to
14.230 MHzand at night, generally will be tuned to
3.845.00 MHz to try to catch some images there, but we aren't always around to change it, so during the night
time hours don't expect many images to be received.
The main page of slowscantv.com (.net .org and .info will all work too) shows the different SSTV web cams from
various locations. When you first visit the page, you are shown the different web cams as though you are located
in our zip code (55430), but you can change the zip code to your location so that the images will be shown in
ascending order of the distance from your location. The further down the list, the further the web cam is away
from you. If you are located somewhere that doesn't use zip codes, you can enter your latitude and longitude to
sort the images also. The location information is simply set in the URL after you enter your location. Clicking
on any image that is displayed will take you to the website of the web cam whose image you clicked on. If you want
to prevent your browser from moving away from our site, simply middle click, or right-click and open in new window
or tab, or press Alt-Enter after entering a URL manually and the other web site will open in a new window or tab
depending on how you have your browser set up.
If your are viewing our image history page, you will see the full-sized images 3 per row. Each image includes the
image number, which indicates where it is on the page, the file number, which is the number that was assigned to the image by our software when it
was originally moved to the server, the mode that was used to transmit the picture and the date and time the image
was saved to our computer. Every 3rd row has a link that will bring you to the bottom of the history page where you
can enter new parameters to filter which images will be displayed.
That's basically it. If you have any questions or suggestions, feel free to email us at webmaster at slowscantv.com
Thanks! Tom / W1SDM & Grace / KC0UQY
