APRS Digipeatersoftware DIGI_NED
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HF-gate

Who uses APRS on HF? Some home stations do, but it's really suited for mobile travelers who are outside of a local VHF RF infrstructure. There are still some maritime mobile HF APRS uses, but even so most of those those stations are using WinLink2000 which has a GPS position link and all those positions are gated over to the APRS-IS.

For those stations that want to experiment with a APRS gateway this information will be of value.

Basically, no path is needed since digipeating on HF is almost useless due to the constantly-changing propagation. If you are determined to try to get digipeated on HF, the path command "ECHO" is analogous to "RELAY" on VHF. Normally, you shouldn't need digipeating on HF. Many HF fixed stations are listening silently on 30M (i.e. no beacons to announce their presence) but are I-gating whatever they hear to the Internet system.

Some HF-gates can re-transmit what they hear on HF onto 2M where then (hopefully) a normal 2-meter igate will insert the packet into the APRS Internet system. The command to make this happen is "GATE" in the path. Thus you might use the path: "GATE,WIDE2-1" or "GATE,WIDE2-2". This would cause your packet to be retransmitted onto 144.39 (US) or 144.800 (EU) and THEN get digipeated once or twice on 2 meters. This can result in multiple reports entering the Internet system since an HF station may igate you directly off HF, and then later a second copy of the posit reaches the Internet after being retransmitted on 2 meters.

Capacity of a single HF frequency.

Remember that an average length APRS Posit packet takes 3 to 4 seconds to transmit on HF. Assuming a channel efficiency of 30% for ax25 this results in a maximum of 7 stations being able to transmit per minute. At a transmission rate of one posit per 10 minutes the maximum number of stations that can be in a single APRS Gate?s coverage area is 70 stations. This will be less when the Net stations transmit frequently and messages and/or tuning may be under way on the channel. HF Propagation is also an important factor in limiting station numbers

Be aware that a badly configured digi on HF can make the frequency un-useable.
Perform your experiment with care.

PLease concider these guidelines when operating your digi on HF:

  • You are sharing a single frequency on HF with hundreds of other operators.
  • Use a SSID of -4 if your station is an HF to VHF (or IS) Gate.
  • Keep your packet size to a minimum. Use the Mic-e or APRS compressed position format for your beacon and no or minimal information in your status text.
  • Your postion beacon should be set to 10 minutes or more.
  • the HF port should have the alias ECHO and have a digipeat rule
  • Suggested TNC settings on the HF port are: TXDelay 400ms, PACket LENgth 128, SLOTtime 300ms PERsistance 64ms.
  • Do not digipeat any packets on HF (the only exception is for tuning your radio, eg. ECHO).
  • Do not feed VHF or IGate data to HF

Example config file for HF-gate.

digi_ned.ini

;------------------------------------------------------------------------------
; DIGI_NED as a HF-gate.
;
;version: 2
;
;------------------------------------------------------------------------------
;
; Start of the rules,
; every 10 minutes compressed beacon on both bands,
; every 30 minutes on VHF full position beacon,
; every 6 minutes digi status locally.
;
; Beacons
;
beacon: 30 2 DIGI_DEST,WIDE4-4
digibcon.ini
;
beacon: 10 all U2QPU6
digicomp.ini
;
send: 6 2 DIGI_DEST
digi_id.ini
;
;------------------------------------------------------------------------------
; Generic digipeating rules, gate:
; - from 1 to 2 and from 2 to 1
; - from 1 to 1 only HF
;
; Port 1 = HF
; Port 2 = VHF
;
digipeat: 2 gate 1
digipeat: 1 gate 2
digipeat: 1 local 1
;
;------------------------------------------------------------------------------
;
; These are all default values for more info see the digi_ned.ini.txt file.
;
;ssid_ignore_prefix: ~
;
size_heard_list: 300
;
size_heard_show: 16
;
keep_time: 1740
;
short_keep_time: 10
data_prefix: :?
;
message_file: digi_ned.mes
;
message_keep_time: 900
;
message_path: all
;
max_msg_hops: 2
;
digi_pos_file: digiaprs.ini
;
dx_times: all,2
;
dx_metric: km
;
dx_level: all 25-10000 1
;
; DX only on VHF and only local. Do not use long path and prevent the VHF network from flooding.
;
dx_path: 2 DX
;
dx_portname: 1 HF
dx_portname: 2 VHF
;
block: N0CALL,NOCALL,MYCALL,TNC,PK88
;
;allow_to: 2 MAIL*,FBB*
;
;allow_from: 1,2 PE*,PA*,PI*
;allow_from: 2 PD*
;
msg_block: N0CALL,NOCALL,MYCALL,TNC,PK88
;
kenwood_mode: 1
;
digi_owner: PE1MEW
;
enable_exit: 1
;
;tnclogfile: digi_ned.tnc
;
digi_call: PE1MEW-2
;
; replace digi_dest with the vesrion of DIGI_NED you are using
;
digi_dest: APNDxx

The used files: (these are suggestions)

digibcon.ini

!5209.71NS00548.98E#PHG4630/RadioKootwijk http://go.to/pi1apk mail:pi1apk@go.to

digicomp.ini

`{N l+_#S

digi_id.ini
>HF-GATE operational

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