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ZL3AI > APRDIG 29.10.06 22:00l 145 Lines 5644 Bytes #999 (0) @ WW
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Subj: [APRSSIG] Vol 28 #22, 1/1
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From: ZL3AI@ZL2BAU.#87.NZL.OC
To : APRDIG@WW
Today's Topics:
1. Beeline GPS (John Habbinga)
2. RE: Too many digi's ? (Robert Bruninga)
3. RE: Too many digi's ? (Robert Bruninga)
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Message: 1
Date: Sat, 21 Oct 2006 20:22:42 -0500
From: "John Habbinga" <kc5zrq_at_gmail.com>
Subject: [aprssig] Beeline GPS
Since I've just installed a receive-only I-Gate for APRS on UHF, I have
been considering purchasing a Beeline GPS tracker. Has anyone ever used
one. I'd like to know your opinions.
A link to there website is http://www.bigredbee.com/beelinegps.htm.
--
John Habbinga, KC5ZRQ
Lubbock, Texas
http://find-you.com/cgi-bin/find.cgi?call=KC5ZRQ*
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Message: 2
Date: Sun, 22 Oct 2006 11:52:20 -0400
From: "Robert Bruninga" <bruninga_at_usna.edu>
Subject: RE: [aprssig] Too many digi's ?
>... Dual receive sounds like a better step but it
>raises the complexity. Sometimes you can't do this
>at the mountain digi because of logistics.
Dual receive is a great way to cut collisions almost in half. It simply
means putting two TNC's and TWO receivers at the digi each connected to
small 2 element beams or so. Just something to give about 10 dB or more
difference in receiving on one side of the mountain to the other side.
This way, each side can hear two packets at the same time that otherwise
would have collided, but becauise of the different antenna patterns, the FM
capture efffect makes sure each one is heard OK.
Then they both feed tehe same transmttter but with their PTT's
crossconnected to the External Carrier Detect input of the TNC. That way,
they do not collide at the transmitter. You could even do this for three
TNC's and 3 receeivers if the geography of the high site digi has that kind
of groupings. This would triple capacity.
De Wb4APRR, Bob
>Perhaps the thing to concentrate on after the new paradigm is
>establishing power recommendations for stations?
>
>73 de Pat --- KA9SCF.
>
>
>On 10/20/06, Keith - VE7GDH <ve7gdh_at_rac.ca> wrote:
>
>Bob WB4APR wrote...
>
>>That is another way to do it, but the alt-input digi takes only
>>the setting of the -600 offset at the digi and it's done.
>
>But if this is a single transceiver listening on 144.990 and transmitting
>on 144.390, it would be transmitting blind without listening on 144.390.
>It's a nice idea, but wouldn't it really take two TNCs & two radios to do
>it properly... or at least one TNC & a transceiver on 144.990 / 144.390
>plus a receiver on listening on 144.390 to at least listen to see if the
>frequency was clear? Of course, in busy areas, it may never be clear.
>Perhaps it would be no worse than mobiles transmitting from an RF
>black hole and not knowing that someone the next valley over was
>already beaconing.
>
>73 es cul - Keith VE7GDH
>--
>"I may be lost, but I know exactly where I am!"
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Message: 3
Date: Sun, 22 Oct 2006 12:01:31 -0400
From: "Robert Bruninga" <bruninga_at_usna.edu>
Subject: RE: [aprssig] Too many digi's ?
>>...the alt-input digi takes only the setting of
>>the -600 offset at the digi and it's done.
>
>But if this is a single transceiver listening on
>144.990 and transmitting on 144.390, it would be
>transmitting blind without listening on 144.390.
>It's a nice idea, but wouldn't it really take two
>TNCs & two radios to do it properly...
It depends on what you are tyring to do. If it is a High mountain digi
that covers hundreds of APRS users, then one reason for doing this is to
give LOCAL priority to LOCAL users. If the -local- packet steps on 144.39
QRM from surrounding digis that are a hundred miles away and are of less
value than local traffic, then I see no problem with it. It is simply a
way of giving local packets local priority.
Or another way to look at it, is a mountain digi that only serves a few
tens of users in a large area, but who have nothing in common with the
users in the next state who are colbbering this digi with out-of-area
packets that are generally of no interest to this area. Many digis are
hearing 95% or more of the channel busy without out of area packets and
these all collide with locals making their local LAN have poor reliability.
By making this an alt-input digi for locals, now then these local packets
have priority over all external packets. Since the dozens of local users
are typically only 5% of the overall packets this digi is hearing, this
gives these locals 100% priority but only at the expense of about a 5%
impact on still seeing out of area packets.
In otherwords, the alt-input digi gives absolute priority to local packets
and then "allows" out of area packets to be heard too if the local channel
is momentarily quiet.
But if the local area does want to preserve out-of-area packets as well as
locals ones, then you are correct that dual receivers will be needed to
avoid colisions of the local and distant packets at the transmitter.
>or at least one TNC & a transceiver on 144.990 / 144.390
>plus a receiver on listening on 144.390 to at least listen to
>see if the frequency was clear? Of course, in busy areas,
>it may never be clear. Perhaps it would be no worse than
>mobiles transmitting from an RF black hole and not knowing
>that someone the next valley over was already beaconing.
Yes, that is about what it is like. It gives local packets Brick-bat
priority over out of area packets...
Bob
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