HF.txt 6.8c              HF APRS BOAT AND RV TRACKING NET

New in 6.8c:
    * Now HF/VHF switches the PK-232 also
    * Added 2port command so that KAM will transmit on VHF & HF at same time
    * See DUAL PORT sections below

HF FREQS:  MFJ/KAMS  AEA'S    Mode  NORMAL USAGE
            10.151   10.1515  LSB   Mostly East Coast so far (Calif late eves)
             7.085    7.0855  LSB   Mostly West Coast
            14.0963  14.0958  USB   Proposed new APRS DX freq
      
The 7 MHz frequency has a lot of QRM, but is good for shorter range APRS
mobile during the day.  Both the 10 and 14 MHz frequencies were very carefully
chosen to minimize interference to all present users of the band and to
provide some measure of QRM reduction to ourselves.  Please note the SIDEBANDS
used.  These are important and here's why:

30 METERS:  By using 10.151 LSB, the packet signal RF energy is 1.7 Khz
lower and is inside the band edge by 700 Hz.  The sideband energy is down by
40 dB which meets the FCC requirements for band edge operation.  I use the LSB
convention in specifying the freq to be compatible with other packet channels
on the band.  Of course, you can operate on 10.147.6 USB which is exactly the
same frequency!  ALSO PLEASE NOTE that these freqs assume an audio modulation
center frequency of 1700 Hz.  Some other TNC's (PK232) use tones centered at
2210 Hz or 2125 Hz.  Radios connected to these TNC's need to be tuned 510 or
425 Hz higher using LSB and 510 or 425 Hz lower on USB.

20 METERS:  By selecting the frequency of 14.0963 UPPER SIDEBAND we
are in effect radiating on 14.098 MHz.  This frequency is a full 2 KHz away
from the international CW Beacon frequency of 14.100 which SHOULD NOT BE USED
FOR PACKET.  The advantage of this 14.098 frequency is that it can also be
described as 14.0997 LSB for 1700 HZ packet or 14.1002 for LSB with 2200 HZ
tones.  These are exactly the frequencies that all other packet stations might
be trying to avoid if they do not understand the LSB offset!  In effect, we
are taking advantage of their missunderstanding.  To further clarify this
nuance, it is important to note that a packet station desiring to avoid the
CW BEACON frequency of 14.100 should actually never operate within 500 Hz of
14.1017 LSB with 1700 HZ tones or 14.1022 LSB with 2210 Hz tones!  Putting it
a third way, we would be crucified if we announced that we are operating on
14.100 LSB by all those who do not understand LSB offsets.  So we are just
calling it 14.0963 USB to avoid the controversy.  In any case, we are 2 KHz
away from the TRUE CW BEACON FREQ!

     If we use this 20 meter freq for casual APRS DXing and new user familiar-
ization, then we will remove some of the QRM from the 10.151 LSB national
APRS tracking frequency.  I expect this summer, 1994, to see a big increase
in the number of boats and RV's tracked.  In the future, we should also find
a single APRS frequency on 18 and maybe 24 MHz.  Any pioneers?


TUNING:  To aid in tuning into an APRS HF net, I am suggesting that ONE 
station on each frequency be designated as the frequency CZAR.  That station
should set his HF alias to TUNE.  Any newcommer on frequency that desires to
lock onto that station, simply sets his UNPROTO path to go via TUNE
temporarily.  Then he hits several PINGS.  As each Ping is digipeated bcak,
he can tune his receiver right on frequency.  This is the normal netting
procedure, but by using the generic alias of TUNE, a newcommer does NOT have
to know who the CZAR is in order to find the exact frequency.  To avoid
excess digipeating, the station must remove TUNE as soon as he is finished.
Others should keep an eye on the DIGI page and remind anyone that forgets
and leaves TUNE in his path.  It may be possible to have additional slave
TUNE's on frequency (TUNE1,TUNE2), as long as they make a DILLIGENT effort
to zero to each other.  A new user getting no response from TUNE can then
try TUNE1 and TUNE2 in turn.  Obviously these other slaves should be very
widely separated.


HF OPERATIONS:  The HF/VHF modes in APRS only change the packet timing to
account for the slower channel.  They also will shift the TRANSMIT port on
the KAM and shift the PK-232 between VHF and HF operation.  For other dual
band TNC's, you must do this manually using the OPS-COMM dumb terminal mode
to change bands according to your TNC instructions.  When you configure APRS
for HF instead of VHF, it simply multiplies all timing routines by 2 to make
up in the difference between 1200 with digipeaters and 300 baud without.  One other
thing it does is to change your default ALIAS from the generic callsign of
RELAY to the generic callsign of ECHO.  Read the info on the UNPROTO command
and in the DIGIs.txt to fully understand the implications of the generic
alias of RELAY used by all VHF APRS stations.  Obviously, for a nationwide HF
net, we do NOT want anyone digipeating everyone else's packets!  So the change
to the alias of ECHO is important in that it REMOVES the generic ALIAS of
RELAY!  For special operations only, of course, you can still digipeat your
HF packets off of another station under critical or emergency situations,
but you should specify exactly who, by callsign, NOT by the generic call of
ECHO.  (Only digipeat via ECHO if you are in extremis!)


KAM DUAL PORT OPERATIONS:  New in version 6.8c, when APRS is configured for
HF using the KAM, AND the CONTROLS-2PORT command is given, the KAM will not
only send out packets on the selected port, but APRS will also send out
duplicate packets on the other port by using the stream switch character. 
These characters are ~ for HF and | for VHF.  Only the following packets
are duplicated:  BEACON, POSIT, OBJECTS, MESSAGES, and ACKS.  All other
packets are only sent on the selected port.


GATEWAYS:  By assigning the generic callsign of GATE to the gateway function
in the dual port Kantronics or AEA TNC's, any HF station can gate-way into
the local VHF net.  HF stations can probably use the VIA path of GATE
most of the time, because the slow HF operation could hardly clutter up any
local VHF APRS networks.  But users on VHF APRS networks should NEVER use
GATE on the VHF side of their gateways except under extreme circumstances.
This is because there are hundreds of times more VHF users than there are HF
users and the 1200 baud users would totally saturate the HF net!

     To repeat:  The purpose of HF/VHF gateways is to permit VHF local area
APRS nets to see the movements of nationwide RV and BOATER mobiles.  For
example, when I go GPS mobile, I do not want to, and cannot leagally leave my
HF station running at home so my wife can follow my status.  But If I send my
HF mobile APRS reports via the local HF GATEway, then my wife can see me on
our computer which only needs to have a VHF TNC.  Please DO NOT GATEWAY from
VHF through a gateway ONTO HF!


KAM GATEWAY SET UP:  You may connect two or more KAMS, each with an HF radio
on different HF frequencies.  The audio of their VHF sides are tied together
into a low power VHF radio on 145.79.  Both KAMS run with the GATEWAY callsign
of GATE so that any HF APRS packets using the VIA path of GATE will be seen
on our local 145.79 APRS net.

    The HF and VHF parameters for the KAM Unproto command are separated by a
slash character as follows:

UNPROTO APRS VIA HFDIGI1,HFDIGI2/APRS VIA VHFDIGI1,VHFDIGI2 etc

To set up your KAM using the APRS UNPROTO-VIA command, you need to remember to
include the second half of the command as noted above.  If you omit the second
half of the command, then the KAM applies the Unproto command identically to
both ports.  Since I want my KAM to go out on VHF via the local WIDE area
digipeaters (WIDE,WIDE) but I want the HF packets to go via any HF GATEway
node (GATE), I can do that via the APRS UNPROTO command with the following:
    ... Enter new VIA path:  GATE/APRS VIA WIDE,WIDE
Notice that APRS automatically inserts the UNPROTO APRS VIA ... for the first
part of the UNPROTO command and all I have to do is type the DIGI address
(GATE here), but for the dual port KAM, that I must type "APRS VIA" again
myself after the slash for the second half of the command (for the VHF port).


OTHER BANDS:  I only have two HF radios, which is why I have not looked for
other APRS packet frequencies on the other bands.  I would avoid the QRM on 20
meters and would look next on the 18 MHz band for a good permanent APRS report-
ing frequency for the long haul round-the-world boaters.  Of course, the 20 m
frequency would be fun for just working APRS HF DX and seeing where those
foreign stations are!   Remember that APRS can also plot stations using only
grid squares.

HF TRACKING DEMONSTRATIONS:  To see the results of some actual APRS HF
tracking events, use the FILES-REPLAY command to replay the ACADEMY.HST file.
The boats were transmitting once every 10 minutes or so.  My first HF mobile
excursion was over Xmas 93 holidays.  When I returned 2 weeks later the file
XMAS93.hst showed me all that was received in Annapolis of my journey (before
the computer crashed).  It shows good tracking from Knoxville TN to Florence
Alabama.   In fact, N2CZF (then in NJ) was able to track me all day, just
about everyday, for the two week period, during daylight hours!

