[aprssig] APRN news from Dayton!

Wed May 25 02:59:10 EDT 2011

On 5/24/2011 9:13 PM, Scott Miller wrote:
>> Do you mean he has now encased the naked SSTV cam shown on his website at:
>>
>> <http://wiki.argentdata.com/index.php/SSTVCAM> ?
>
> It's a different camera module, but still naked - I gave up trying to find an 
> enclosure form factor that would work for everyone and decided to make it an 
> easily embeddable thing.  The new one has #2-56 screws holding it together 
> and you could use longer ones to mount it in a case.
>
>> documentation of disasters or anything else. Fine details (parallel
>> clapboard siding, fences with parallel wires, overlaid text,etc) aliases
>> into shimmery rainbows of colored fringes on contrast lines.
>
>    You select which mode you want by grounding a combination of two pins.

I noticed that in your wiki docs on the device.   (I assume the wiki docs are 
the ones for the newer unit.)    I am seriously considering using the device as 
my next-gen mobile LiveCAM .     I'm thinking that this assembly is small 
enough and light enough to Velco to the back side (i.e the side facing the 
windshield) of the rear-view mirror so it could get a good look forward with 
nothing in the way.

There is a huge difference between Robot and Scottie modes when you overlay 
small point-size text.   As received on mmSSTV, the Robot modes produce 
shimmery rainbows and colored halos around text -- the Scottie modes 
don't.      All the SSTV modes, except Robot use pure FM audio subcarriers.  
The Robot modes use a PHASE-shifted audio sub-carrier for the color information 
in a manner somewhat analogous to NTSC.     On HF, constantly changing 
propagation paths over long distances really mangle the phase-sensitive Robot 
images, often causing  weird color shifts in parts of the picture.  On 75 
meters at night (where  selective fading and phase shifting are usually quite 
extreme), Robot is virtually unusable.    The other modes, including Scottie, 
that use pure FM are relatively unaffected.

I always use the Robot 36 mode for calling CQ with just 2 or 3  lines of text 
-- something like:

     CQ   de  WA8LMF
Mobile  SSTV  LiveCAM

rendered in a font large enough to completely fill the 320x240 screen.  I use 
the R36 mode to get the simple CQ slide out almost three times as fast as 
Scottie 1, since I don't really care about the color rendition.  (The clueless 
newbies on SSTV that take almost two full minutes to send a simple  "CD DE 
callsign", using the default template in mmSSTV, on Scottie 1 waste an enormous 
amount of air time on 20 meters -- it's the same sort of unthinking channel 
capacity waste as beaconing WIDE1-1,WIDE2-2 every thirty seconds on APRS)       
In fact, I am noticing a retro movement by the more knowledgeable slow scanners 
on HF to revive the use of the classic B&W 8 mode to get full screen monochrome 
CQ slides out in only 8 seconds.  [The 128 line 8-second SQUARE monochrome 
image is the ORIGINAL SSTV format from forty-plus years ago.]

However, when I get ready to send actual live photos, I always use the Scottie 
or Martin modes.  Or PD160 for "HD" full 640x480 VGA pictures.

>
>
> The SSTVCAM has a 640x480 camera, and in the future I might experiment with 
> some higher resolution modes. 

It needs the PD120 or PD140 mode to send full 640x480 VGA.

> But yeah, it's not going to match a cell phone or PC.  It's intended to fill 
> specific niches like high altitude balloons.  It weighs an ounce or so, draws 
> a few mA when it's idle and maybe 30 mA average while transmitting, and works 
> great for one-to-many transmissions where you don't have an opportunity for 
> retries.
>

That was my first thought - lack of a view finder is irrelevant if there's no 
one around to look at it......

Someone else in this thread brought up the issue that the caption at the top of 
the frame needs to be reloaded after every transmission.  Is this true if you 
leave the unit powered up between transmissions?  What about auto mode where it 
spontaneously sends a pic every  xx  seconds.   Can you load the title bar once 
and have it repeated on every transmission?     [I am visualizing driving down 
the Interstate with the mobile LiveCAM looking out the front window, 
automatically sending a pic on 20 meters every three minutes with the caption 
on the top of the picture saying something like    "WA8LMF Mobile LiveCAM  
Colorado I-70"   on each transmission.]

Finally, is the lens on the unit removable?     Can you substitute various 
focal-length lenses of the type used on small security cameras?    (I'm 
referring here to various-value fixed focal-length lenses, not zooms.)

I ask because in  many cases (definitely the case with the VC-H1 camera head), 
these small CCD cameras come supplied with excessively wide field-of-view 
lenses that make objects of interest in the picture just too small. 
(Apparently, for security applications, the assumption is that you want to be 
able to see the entire room -- never mind that there's then not enough detail 
to recognize the face of the burglar.)

Given the severely limited resolution of SSTV, I am always trying to get the 
subject of interest to fill up more of the picture.    Usually, I find that I 
want a lens that produces a field-of-view equivalent to a 55mm "standard" lens 
on a 35mm camera, when all too often the provided lenses are more the 
equivalent of a 28mm  or 35mm wide angle.

-------------------------------------------------------------------------------

--

Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      WA8LMF  or 14400    [Think bottom of the 2M band]
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

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