| |
ZL3AI > APRDIG 19.05.04 09:20l 236 Lines 9419 Bytes #999 (0) @ WW
BID : 3288-ZL3AI
Read: GUEST
Subj: TAPR Digest, May 04, 5/6
Path: DB0FHN<DB0RGB<DB0MRW<DB0SON<DB0ERF<DB0FBB<DB0GOS<DB0EEO<DB0RES<ON0AR<
ZL2TZE<ZL3VML
Sent: 040519/0621Z @:ZL3VML.#80.NZL.OC #:24335 [Chch-NZ] FBB7.00i $:3288-ZL3AI
From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Smarter Squawkers [was Armchair Lawyers]
From: "KC2MMi" <kc2mmi@verizon.net>
Date: Tue, 4 May 2004 16:48:29 -0400
X-Message-Number: 31
<Hmmm. I suppose I could set up my tracker firmware to keep track of how
often it holds off on transmit because the channel is in use.>
Scott, here's an idea for you. Your box is going to have brains, right? So,
why not have it take note of the times that it had to hold off transmitting,
and then use a smart algorithm to give itself an offset that produces fewer
problems?
i.e.:
Wants to xmit every 10 minutes.
Has to hold off at 12:10, someone else is on the air
Shifts offset to 12:11.
Gets more interference and holds? Or less?
And continues to shift itself, as needed, until it finds an empty timeslot.
I suppose ideally you could take that idea and run with it...
....Forgive me! But then why not add a routine for the digi's themselves to
talk back to the boxes they hear, and say "OK, you, shift 38 seconds, and
you, shift 93 seconds...." and do the air traffic controller routine IN the
system? Why not make the technology adaptive, instead of assuming there will
be interference and repeatedly ignoring it?
'sall donkey work, and computers are good at that. The rest is just a simple
exercise, left to the programmer.<G>
----------------------------------------------------------------------
Subject: RE: HF ALE
From: WB4GQK@aol.com
Date: Tue, 4 May 2004 16:52:21 EDT
X-Message-Number: 32
Jack presented some interesting points in his post 5/4/2004
>..................: ALE does not appear to be allowed under current FCC
>rules in the United States. These rules limit digital transmissions to
>about 500 Hz. ALE occupies about 2.8 kHz or the width of a voice
>channel.
I would estimate there are well over a 1000 U.S. hams using PACTOR III
modems and connecting into WINLINK stations. I for one. These SCS PTIIe
modems (which are not cheap) transmit with a passband of 2.2 KC! And take
the time to listen on 30 Meters to a large number of them in operation and
scan their bandwidth. I was not aware that these PACTOR III systems were
not allowed in the USA! But they will pass 2400 baud quite easily specially
with mailbox stations such as K4CJX and KN4RB.
>Here is a thought for HF APRS: Use Pactor FEC. It allows the full
>ASCII character set; it is analogous to an unconnected packet; it is has
>some error correction and is about 10 times faster than PSK31 including
>QPSK31 which has FEC.
I agree PACTOR III is faster than PSK31 but now I am wondering if it's
legal? Anybody got the straight skinny on this mode?
73 de Jim
----------------------------------------------------------------------
Subject: Re: Smarter Squawkers [was Armchair Lawyers]
From: "Scott Miller" <scott@opentrac.org>
Date: Tue, 4 May 2004 14:01:02 -0700
X-Message-Number: 33
>...Forgive me! But then why not add a routine for the digi's themselves to
>talk back to the boxes they hear, and say "OK, you, shift 38 seconds, and
>you, shift 93 seconds...." and do the air traffic controller routine IN the
>system? Why not make the technology adaptive, instead of assuming there will
>be interference and repeatedly ignoring it?
I was thinking you could have each digi announce a bitmap indicating average
channel load for each one-second period during the minute. Trackers would
tend toward the less-loaded slots, randomized to some extent by their
callsign/ssid to prevent everyone from choosing the same unloaded slot.
Kind of like how they don't give paratroopers fully steerable parachutes,
because they all pick the same nice landing spot, given a choice...
Scott
N1VG
----------------------------------------------------------------------
Subject: Re: Slotted ALOHA
From: Henk de Groot <henk.de.groot@hetnet.nl>
Date: Tue, 04 May 2004 23:40:50 +0200
X-Message-Number: 34
At 22:19 3-5-2004 -0500, David VanHorn wrote:
>On second thought, no it dosen't, if you use time as the slotting mechanism.
>Count an interval of say 300 seconds in 5 sec intervals, and pick any
>interval as your slot.
This will work as long as the start points of the slots are alligned in
time for all clients, since that is where the advantage is. Also the slots
need to be big enough to accomodate for a worst-case packet. If a slot of
one system overlaps two slots of another system then you're back to Aloha.
Most packets will be about 1 second in lenght, a 5 second slot is a bit
wide. It also means that in 60 seconds you can have 12 seconds worth of
packets, thats a utilisation of 12/60 bu= 0,20 -> 20%. This is not an
advantage. Slotted Aloha shines for fixed-length packets, but I think it is
a bit of a waste for variable length APRS packets.
For this to work the clients also need to be synchronized so that each
client knows at what point in time the next slot starts. This can be done
either by means of a universal standard like GPS timing or by a
synchronisation signal from the digipeater (where multiple digipeaters also
need to be synchronized with eachother).
But the key question is: does it work on Kenwoods. If you answer that one
then you know hou much chance your proposal has...
Kind regards,
Henk.
----------------------------------------------------------------------
Subject: Re: Garmin 38 Voltage?
From: "Mike Yetsko" <myetsko@insydesw.com>
Date: Tue, 4 May 2004 17:19:37 -0400
X-Message-Number: 35
>Has anyone used a simple resistor to reduce
>the voltage to a Garmin 38 from the 14v
>automobile to the 6 volt input? In otherwords
>is the 5-8 volt input requirement due to power
>dissipation concerns or instantaneous voltage?
>
>At 150 mA, looks like a 60 ohm 2W resistor
>would do it if the instantaneous voltage transient
>is not a problem..
>
>Bob
I think you're playing with fire. From what I've heard, the older Garmin's
with the 8v 'limit' really mean at just over 8v they let all the smoke out.
Isn't the current draw kind of variable on the 38? At least enough that
you would be dangerously variable? To say nothing of the car swinging
around from 11v to 14.3v or higher?
Why not just use a 7805 with a diode on the 'ground' to boost it to 5.7v,
or 2 diodes to 6.4v? Or a 7806 (ok, hard to find for most hobbyist)?
Or, not quite back to basics, an LM317 with a resistor set!
Mike
----------------------------------------------------------------------
Subject: Re: Slotted ALOHA
From: "Curt, WE7U" <archer@eskimo.com>
Date: Tue, 4 May 2004 14:55:04 -0700 (PDT)
X-Message-Number: 36
On Tue, 4 May 2004, Henk de Groot wrote:
>Most packets will be about 1 second in lenght, a 5 second slot is a bit
>wide. It also means that in 60 seconds you can have 12 seconds worth of
>packets, thats a utilisation of 12/60 = 0,20 -> 20%. This is not an
>advantage. Slotted Aloha shines for fixed-length packets, but I think it is
>abit of a waste for variable length APRS packets.
Another reason to go with Compressed packets/Mic-E/OpenTrac: Shorter
packets.
>For this to work the clients also need to be synchronized so that each
>client knows at what point in time the next slot starts. This can be done
>either by means of a universal standard like GPS timing or by a
>synchronisation signal from the digipeater (where multiple digipeaters also
>need to be synchronized with eachother).
There's a difference in timing coming out of the GPS'es as well, and most
don't have PPS outputs. A change in the baud rate will change the timing
to the device parsing the stream. You might need extra wide timeslots to
accomodate this slop in the low-end GPS outputs.
--
Curt, WE7U archer at eskimo dot com
Arlington, WA, USA http://www.eskimo.com/~archer
"Lotto: A tax on people who are bad at math." -- unknown
"Windows: Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me: I picked the coordinate system!"
----------------------------------------------------------------------
Subject: Re: OT? Garmin E-Trex setting
From: "Richard Amirault" <ramirault@erols.com>
Date: Tue, 4 May 2004 18:04:34 -0400
X-Message-Number: 37
Sorry, I can't help .. but thanks for the 'heads up' on this .. I have a
basic (yellow) eTrex that I have rigged for a tracker (but only used it for
an event once) .. "normally" I use my Garmin GPS III and I know (from
experience) that it do what you wish ... wonder why Garmin has different
units act differently?
Richard Amirault N1JDU Boston,
MA, USA
www.erols.com/ramirault "Go Fly A Kite"
----- Original Message -----
From: "Alton (XP machine)"
Subject: [aprssig] OT? Garmin E-Trex setting
(snip)
>With vibration going down the road, sometimes the unit "thinks" external
>power has been lost and "conveniently" powers itself down if no human
>happens to see the warning screen in 30 seconds or so.
>
(snip)
>Desired behavior - if external power is lost (or intermittent), keep the GPS
>powered on and feeding data to the TinyTrak until the batteries run down and
>die. Batteries are cheap.
>
>If external power is restored 20 minutes later, it should just run off
>external power until it vibrates loose again, and then stay running until
>someone notices and shoves the lighter plug the rest of the way into the
>socket or the batteries finally die.
(snip)
----------------------------------------------------------------------
Read previous mail | Read next mail
| |
