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ZL3AI > APRDIG 31.01.04 13:45l 243 Lines 9516 Bytes #999 (0) @ WW
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
TAPR APRS Special Interest Group Digest for Thursday, January 29, 2004.
1. Re: SSTV question
2. Re: Dumb tracker GPS Map displays
3. Re: SSTV question
4. APRS Igate in Japan
5. Re: Dumb tracker GPS Map displays
6. Packet/PSK-31 shared transponder?
7. Re: Dumb tracker GPS Map displays
8. Re: CW???? station display
9. APRS Symbols update
10. APRS on MARS and the MOON.
11. Re: APRS on MARS and the MOON
12. Re: APRS on MARS and the MOON
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Subject: Re: SSTV question
From: "Stephen H. Smith" <WA8LMF2@aol.com>
Date: Thu, 29 Jan 2004 05:05:09 -0800
X-Message-Number: 1
Scott Miller wrote on 1/28/2004, 4:21 PM:
>The reason I'm asking is that I'm still thinking about an idea for a
>cheap
>hardware SSTV encoder. Old parallel port QuickCams are available dirt
>cheap
>on eBay, and information is available on how to interface them to a
>microcontroller. The camera's got its own internal frame buffer, so
>depending on the output format it may even be possible to generate the
>signal on the fly as data is clocked out of the camera.
1) A year ago, I saw a web page that had a rundown of the various SSTV
standards. I think I captured it and am now looking for it among my
thousands of misc techical notes capped from the web.....
2) The image quality of cheap webcams is so appallingly bad, I doubt it
would be worth the bother. Especially since these devices almost always
have rather wide angle lenses that make any given object in the view too
small to cover enough pixels to be clearly resolved. An aerial photo
produced by such a device tends to be just a greenish brownish blur with
no details.
3) These cheap webcams are intended for indoor use at relatively low
light levels. Their CCD sensors don't have wide-range automatic light
level controls, and overload badly and wash out in direct daylight.
[ These are the very same limitations as the camera head provided with
the VC-H1 which uses the same sort of cheap 240-line low-res CCD sensor.
To get decent results, especially outdoors, with the VC-H1 you have to
remove the provided camera head and use an external camera - typically a
digital still camera with good automatic exposure control and an NTSC
monitor output. ]
This would be
>a fun
>project for balloon experiments.
>
>I understand there are some formats favored for higher-speed VHF use.
>Are
>there any optimized for 9600 baud capable radios? Seems to me that any
>radio capable of 9600 baud data ought to be able to pump out an analog
>SSTV
>frame pretty quick given the right modulation format.
ALL of the standard SSTV formats were designed for "stick it in the mic
jack" operation on HF SSB radios originally. They use the same FM audio
subcarrier that ranges from 1200 Hz for sync, 1500 Hz for black and 2300
Hz for 100% white. (These standards were borrowed from old analog
"wire-photo" fax standards. Indeed, in the earliest days of SSTV in the
late '50s-early'60s, it was referred to as "cathode-ray faxsimile".)
The differences are in the number of these analog lines sent per second,
duration of the end-of-line sync pulses, number of seconds to send a
complete frame, and color-encoding schemes. The vast majority of SSTV
usage is a 320 pixel by 240 line image (quarter-VGA), although a few
formats support 640x480 standard VGA and one does 600x800 SVGA (with a
far longer transmission time).
Dave VanHorn wrote on 1/28/2004, 5:04 PM:
>Kenwood had their fast-fm format, in the VC-H1s, but I don't know
>where it
>would be documented.
The Kenwood format is digital, not analog and requires direct FM
coupling to the FM modulator (similar to 9600 baud packet TNCs). The
real issue however is that this is a dead proprietary format that was
NEVER supported on ANY hardware or software other than the
now-discontinued-for-over-a-year VC-H1. [ Kenwood shot themselves in
the foot with this one, as they did a decade earlier with their
digital-coded squelch scheme, by trying to keep the format proprietary
and not releasing any technical info so that other devices and software
could inter-operate with theirs. ]
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
Ham Radio/Mobile SSTV page: http://members.aol.com/wa8lmf/ham
APRS Stuff
http://members.aol.com/wa8lmf/aprs
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Subject: Re: Dumb tracker GPS Map displays
From: "Stephen H. Smith" <WA8LMF2@aol.com>
Date: Thu, 29 Jan 2004 05:11:42 -0800
X-Message-Number: 2
Bob Bruninga wrote on 1/28/2004, 1:38 PM:
>If you use a DUMB tracker with a GPS that has MAP displays, remember
>that
>someone can send you OBJECTS that will display on your GPS map just like
>the D7 does. This is useful for SAR or other organized events where you
>may be using DUMB trackers, but need to send OBJECTS to those drivers on
>their GPS maps.
You are assuming dumb trackers implemented with a TNC. I suspect that
that the vast majority of dumb trackers today are implemented with
TinyTraks or TigerTraks which can't receive. [ This is definitely the
case observed from monitoring activity off the air in southern Cal. ]
i.e. why tie up a $150 TNC when you can do the same with a $35 PIC gizmo
that uses 1/50th the power?
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
Ham Radio/Mobile SSTV page: http://members.aol.com/wa8lmf/ham
APRS Stuff
http://members.aol.com/wa8lmf/aprs
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Subject: Re: SSTV question
From: Dave VanHorn <dvanhorn@cedar.net>
Date: Thu, 29 Jan 2004 08:17:42 -0500
X-Message-Number: 3
I would like to work on such a project.
I have done TV-typewriter sorts of things in the past, but I must admit,
how they capture NTSC is beyond me at this point.
Still, I'm an old modem designer, so that end of it is no problem.
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Subject: APRS Igate in Japan
From: Bob Bruninga <bruninga@usna.edu>
Date: Thu, 29 Jan 2004 10:13:41 -0500 (EST)
X-Message-Number: 4
There is an IGate in Japan on APRS 144.64 MHz.
and also a SATGate on PCsat downlink:
JA1YKX or 7J1AJH
Glad to see some APRS in the most populated HAM country.
Bob
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Subject: Re: Dumb tracker GPS Map displays
From: Bob Bruninga <bruninga@usna.edu>
Date: Thu, 29 Jan 2004 11:06:36 -0500 (EST)
X-Message-Number: 5
On Thu, 29 Jan 2004, Stephen H. Smith wrote:
>Bob Bruninga wrote on 1/28/2004, 1:38 PM:
>
>>If you use a DUMB tracker with a GPS that has MAP displays, remember
>>that someone can send you OBJECTS that will display on your GPS map
>>just like the D7 does....
>
>You are assuming dumb trackers implemented with a TNC.
Yes, as soon as I hit send I realized I left out that caveat. But it was
too late...
>I suspect that that the vast majority of dumb trackers today are
>implemented with TinyTraks or TigerTraks which can't receive.
Yes, but hopefully as new people write more and more code and with the
single chip PIC AX.25 receivers now, it is a cabability that should not be
overlooked in future designs.
>i.e. why tie up a $150 TNC when you can do the same with a $35 PIC gizmo
>that uses 1/50th the power?
Agreed. But also many people are sitting on lots of old TNC's that arent
being used...
anyway , just a thought. ANd thanks for the clarification...
Bob
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Subject: Packet/PSK-31 shared transponder?
From: Bob Bruninga <bruninga@usna.edu>
Date: Thu, 29 Jan 2004 11:16:56 -0500 (EST)
X-Message-Number: 6
Packet/PSK-31 shared satellite transponder?
I am looking for a co-author on the design for a combined AX.25 and PSK-31
multiuser FM downlink.
We first began discussing the concept for a PSK-31 uplink and FM downlink
with Roger Marinez back in Feb 2001 and we are flying it on PCSAT2 which
should have already been on orbit except for the slip in Shuttle launches.
We also recommended it for ECHO which should soon be in orbit.
The original target satellite for this transponder was our Cubesat called
RAFT. But since PCSAT2 was short fuse and both it and ECHO will have beat
it to orbit with this transponder concept, we are beginning to consider
not making it dedicated to PSK-31, but sharing it with 1200 baud AX.25
packet.
The usual problem of AGC pumping on the uplink is avoided by separating
the uplinks with PSK-31 on 10m and Packet on 435 MHz. Then only the
constant level audio is combined in to the single 2m FM downlink. I'm
looking for a co-author to help develop this technique. On a quick test,
it looks like the 1200 baud packet occupies about 900 to 2400 Hz leaving
room for about 10 PSK-31 users split evenly above and below.
I'd like to do a survey of typical handheld HT's audio bandwidth, and
match that with our FM transmitter and be able to well characterize the
audio spectrum of the combination of the two modes and filters we will
need. If you are interested in co-authoring the paper on this technique,
lemme know.
See the combined signal on the bottom of this page:
http://www.ew.usna.edu/~bruninga/raft.html
de WB4APR, Bob
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