[aprssig] Fast SSTV for on-air presentations

Mon May 4 19:23:52 EDT 2020

Thanks, good info.  But I disagree about the resolution. *most*
presentations I see are very wasteful of fonts.  They use big fonts and
maybe only 4 bullets per slide.  On the other hand some slides use
painfully small font that are ridiculous.

I always toke care to use large font, and big ideas and graphics that are
representative of concepts and do not need detail resolution.
I think my slides would work OK via SSTV resolution.

But I agree too many presentations are unreadable even at normal resolution
anywhere in the room but the front row.  People just dont have a clue when
they prepare such unreadable presentations.

Bob

On Mon, May 4, 2020 at 4:51 PM Stephen H. Smith <wa8lmf2 at aol.com> wrote:

> On 5/4/2020 12:45 PM, Robert Bruninga wrote:
> > The local radio club wants to move to on-line technical talks but got
> bogged
> > down in arguments over teleconferingin  protocols and security..
> >
> > I's like to transmit my presentation as SSTV FAST mode (13 seconds per
> slide)
> > and give the talk on the local repeater.  The FAST FM mode premiered in
> the
> > (decades ahead of its time) Kenwood VC-H1 And generally has to connect
> to the
> > modulator and discriminator and not the voice circuits.
> >
> > Has anyone used FAST FM mode for SSTV?  Can it be received by most folks
> > without having to get to the discriminator for receive?
> >
>
>
> 1)    NO!  The fast mode is a failed protocol that never gained
> acceptance.  No
> one except owners of the now rare VC-H1 that also have the only radio that
> worked with the VC-H1 in fast mode (the TH-D700) can send/receive it.  NO
> SSTV
> software supports the fast mode.
>
>
> 2)    The resolution of any normal SSTV frame (including the fast mode) is
> only
> 320x240 pixels -- far far too low to reproduce any kind of presentation
> with
> text or detailed graphics such as maps or schematic diagrams.
>
> The only modes to go above the quarter-VGA 320x240 are some of the PD
> modes
> that can do a standard 640x480 VGA (2-3 mins/frame) or SVGA 800x600 (4.5
> mins/frame) image.
>
> Consider that normal PowerPoint presentations typically expect a 1024x768
> XGA,
> 1280x1024 SXGA, 1280x720 half-HD or even 1920x1080 full HD display.  At
> least
> 3/4 of them use far too small text (to cram more onto each page),
> resulting in
> the text being unreadable to anyone but the first row of the audience .
>  Sent
> over low-def bandwidth-limited 320x240 analog SSTV will guarantee that NO
> one
> will be able to read them!
>
> Further, the only way to create "fast mode" images is the unbelievably bad
> low-res camera head of the VH-C1.  I radically improved the sent image
> quality
> of the VC-H1 (on standard SSTV modes) by connecting an external NTSC
> camera to
> it in place of the OEM head. (The jack on the VC-H1 for the camera is
> actually
> a standard NTSC 1-volt P-P composite video input.)
>
>
> 3)    The only way to get the fast mode out of a radio is via the raw FM
> discriminator.  Radios that have the 6-pin mini-DIN "packet" or "data"
> port
> make this easily - one of the 6 pins is the discriminator-out connection,
> sometimes labeled "9600 baud packet".  Full details on the port here on my
> website:
>     <http://WA8LMF.net/6-Pin-MiniDin-Data-Connector>
>
> Unfortunately, fewer and fewer radios are now coming with this port.   I
> am
> painfully aware of this as I struggle to acquire basic monoband radios
> with the
> din port for APRS applications. NONE of the Chinese radios now flooding
> the ham
> market have the DIN port.   Not to mention the god-awful BaoFeng
> disposable
> handhelds that more and more entry-level hams struggle to use on non-voice
> modes, usually with lousy results.
>
> FM/digital Transceivers are evolving toward entire radio-systems-on-a-chip
> that
> include RF, synthesizer, mixers, detector and audio on a single IC,  These
> chip-sets are intended for high-volume cellular devices, but are now
> increasingly appearing in two-way radios as well. This type of design
> makes it
> increasing difficult to "tap the discriminator" (if in fact they even have
> an
> IF & discriminator).  More often they are now direct-conversion DSP
> devices.
> (Nearly all the cheap Chinese radios are of this type.)
>
> I wind up having to pick up second-hand Yaesu FT-1500 2M monobanders off
> eBay
> or at swapmeets for building ammo-can trackers or ammo-can porta-digis.
> Jusat
> last month, I discovered that one of the last small-footprint VHF-UHF
> FM-only
> radios with the DIN port (the Yaesu FT-8900 10-6-2-70cm quad-bander) has
> just
> been discontinued with no replacement in sight.
>
> _____________________________________________
> Stephen H. Smith    wa8lmf (at) aol.com
> Skype:        WA8LMF
> EchoLink:  Node #  14400  [Think bottom of the 2-meter band]
> Home Page:          http://wa8lmf.net
>
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>
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