[OZAPRS] Sydney Basin RF Gating

Mon Aug 28 20:54:35 EST 2006

Hi Mike,

>From what you have written it looks like the APRS RF channel in your area
(VK1/VK2)is overloaded with IGate traffic.

One way to measure this is to use UI-Traffic
(http://www.apritch.myby.co.uk/traffic.htm ) and AGW Packet Engine (AGWPE
-
http://www.elcom.gr/sv2agw/inst.htm ) which measures the number of APRS
packets your station receives via RF. If the number is consistently
greater
than 100 per 10 minutes then the RF channel is considered Over Loaded.

The IGate owners have a responsibility to Co-ordinate Monitor and Manage
local RF channel levels in order to provide a reliable APRS Network for
all.

All APRS operators and especially IGate operators must be aware of the
effect their stations RF transmissions have on their neighbours.

If you would like more information on the APRS RF traffic limitations of
you
can find it at http://www.vk3.aprs.net.au/rf_bandwidth.htm .

Cheers
Richard
VK3JFK

-----Original Message-----
From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
Behalf Of Mike Townsend
Sent: Monday, 28 August 2006 12:29 AM
To: ozaprs at aprs.net.au
Subject: [OZAPRS] Sydney Basin RF Gating

Hello All,
Being relatively new to APRS but now with a little understanding of how
the
system works I have decided to shutdown my Internet to RF port except for
messaging and on a limited as requested basis for position beacons. 
When first becoming involved with APRS I found that I had  a lot of
difficulty in having my Mobile station gated to an Internet server. Was
there RF getting into my encoder. No. How about the power level I was
using,
its recommended that approx 20W when Mobile is more than enough but even
at
50W into a 5/8 th mounted on the roof I was not having much luck. (Usual
operating distance to VK2JPJ-1 being 25 to 40km). 
So I thought I'll setup my own I-Gate at home and see what happens.
Problem
solved with reliable gating out to the North from my QTH here in
Campbelltown, not so good to the South as I'm not quite on top of the hill
and have RF shadowing in that direction when Mobile down the Hume Highway.
Now having an RF receive capability I have been able to monitor the APRS
frequency and see for myself what is happening.  At my home QTH I hear
VK2AMW-1 direct which is used as a Digi for what appears to be the full
ZL/VK server port feed originating from VK1. My TNC DCD LED being nearly
constantly lit. OK, if  I'm copying this how about VK2JPJ-1 which was most
likely to be my point of entery into the APRS network when mobile. So
having
a look at the VK2JPJ-1 heard list,

mh
SYDCBD:VK2JPJ-1} MHEARD:
12:27=VK1NPW-1* 12:26=VK2TSB    12:25=VK1NPW-2  12:24=VK2INT-1*
12:24=VK2INT-1
12:24=VK2EMD*   12:23=VK2JNT-1  12:21=VK2AMW-3  12:19=VK2JPJ-1*
12:19=VK2RAG-1
12:18=VK1RGI-1* 12:15=VK2EMD-4* 12:11=VK1KCM-9* 12:08=VK1VIC-1
12:08=VK2AR-1*
12:07=VK2AR-1   12:05=VK2RAG-1* 12:05=VK2AMW-1  12:04=VK1NPW
12:02=VK2AFY*
11:55=VK2CSU-1* 11:50=VK2AMW-1* 11:47=VK2AMW-3* 11:45=VK1HFC
11:16=VK2AMW-4*
11:07=VK1NFI    10:48=VK2TSB-3* 09:43=VK2DRK    09:39=VK2JGV*
09:39=VK2JGV
09:07=VK2ZSZ    08:59=VK2TDS-1* 08:59=VK2TDS-1  08:31=VK2SX*
08:12=VK2MIK*
07:48=VK2US-10* 07:48=VK2US-10  07:41=VK2INT-9* 07:01=VK2EZD
06:35=VK2TSB*
05:56=VK2HIM-7* 05:53=VK1MRH-9* 05:49=VK2ZSZ-9* 05:30=VK2EZD*
05:09=VK2BES*
04:52=VK2KJB*   04:29=VK2APE-9* 03:37=VK2INT-9  01:18=VK2BES
01:08=VK2EJC-3*
23:55=VK2ZOM-1* 23:13=VK2ZOM-2* 22:55=VK2KCL-9*
22:18=VK2INT-15*22:17=VK2INT-15
19:03=VK2AFY    10:57=VK2KJV*   04:12=VK2ZSZ-8* 02:53=VK2JNT-9*
02:42=VK2JNT-9
10:42=VK2KCM-9* 07:52=VK2LI-9*  07:18=VK2LI-9   05:57=VK1HCT-11
03:22=VK2CAW
06:14=VK2GRM*   03:18=VK2LI*    01:14=VK2ZOM-2  05:12=VK2EJC-3
02:51=VK2HIM-7
23:23=VK3HIV-9* 12:05=VK2INT    07:08=VK2UAI-9* 01:55=VK2AWZ*
01:51=VK2AWZ
03:49=VK2SKY-9* 03:49=VK2SKY-9  01:59=VK2CMO-9* 01:59=VK2CMO-9
22:26=VK2AMW-2*

>From this we see that VK2JPJ-1 is hearing VK2AMW-1 as well as VK1
stations
direct and I thought my DCD LED is busy. I'm assuming that those calls
without a * have been heard direct.
With regard to the above I feel it is not necessary for me to add to the
congestion by gating traffic to RF from the Internet other than that
stated
above. Also adding to my two cents worth is there, with consideration to
the
now widespread use of Broadband, a requirement for all this traffic to be
gated to RF on such a wide scale? As I see it every oppurtunity should be
given to mobiles to access an I-Gate or local Digi. If users or their '
ham
buddies ' can't see much happening because of  lack of mobile position
beacons making it on to the network then they are likely to give up APRS
as
a bad joke.
Please, this is not meant to be criticism of anyone in particular. As I'm
only interested in having a workable RF network available to all.

Regards Mike, VK2INT.

Quote UI-View IGATE.INI

NOTE - The capacity of a 1200 baud RF channel
is around 30 frames a minute (obviously it depends on
frame length, TXD settings, etc). To gate 6 frames in
a minute means that you are taking up around 20% of
the channel capacity, and that's not allowing for your
frames being digipeated! So before you increase these
numbers, please bear in mind that many APRS experts
would say that the defaults are too high. You should
always try to use values that are appropriate for
local conditions.
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