HFNets

HF Nets

The following index has been created to track various efforts to utilize the HF bands for packet activity. There are some existing nets that are primarily focused on casual operating, keyboard to keyboard messaging for personal mail delivery. Due to the nature of AFSK and SSB, it is possible to have many combinations of VFO dial frequency with audio tone selection. Please see WA8LMF's excellent article on their relationship. It is also possible to run multiple, concurrent modems as long as their audio pass range fits within the radio's SSB filter. These ranges can vary, but generally runs around 300-3000 Hz. The two most popular protocols are AX.25/FX.25 (compatible) and IL2P. The AX.25/FX.25 protocols use NRZI encoding, which means USB and LSB can communicate as long as the center frequencies match. The IL2P protocol uses NRZ encoding, which means sideband selection must match. The seeming standard for HF IL2P seems to be USB. For compatibility reasons, it is suggested to run USB for both AX.25/FX.25 and IL2P. This also aligns with VARA, ARDOP and Mercury modems using USB. Traditionally, AX.25 HF packet was LSB by convention, but can support both. For those running hardware based TNCs that do not support IL2P and have fixed tones at 1600:1800 Hz (1700 Hz center), LSB frequencies are provided.

Current HF Packet Nets

Name	Band	Center Frequency	Speed	Protocol	Usage/notes	Dial Frequency+Tone pairs
NET105	20M	14.103.3	300 Baud	AX.25/FX.25	Keyboard to Keyboard	14.102.0 MHz USB, 1300 Hz (recommended) | 14.105.0 MHz LSB, 1700 Hz
NET105	20M	14.104.3	300 Baud	IL2P	Keyboard to Keyboard	14.102.0 MHz USB, 2300 Hz
NET40	40M	7.102.3 MHz	300 Baud	AX.25/FX.25	Keyboard to Keyboard	7.101.0 MHz USB, 1300 Hz (recommended) | 7.104.0 MHz LSB, 1700 Hz
NET40	40M	7.103.3 MHz	300 Baud	IL2P	Keyboard to Keyboard	7.101.0 MHz USB, 2300 Hz
NET80	80M	3.597.0 MHz	300 Baud	AX.25/FX.25	Keyboard to Keyboard	3.596.0 MHz USB, 1000 Hz (recommended) | 3.598.7 MHz LSB, 1700 Hz
NET80	80M	3.598.0 MHz	300 Baud	IL2P	Keyboard to Keyboard	3.597.0 MHz USB, 2000 Hz

These are proposed nets that allow the operator to retain a presence on the NET105/NET40/NET80 keyboard nets, while using audio tone selection to be able operate node hopping and mail forwarding in independent audio lanes. The main drawback to this is the increased co-channel interference brought on by wider bandwidth modes that all must fit in the ACDS subband.

Proposed/Experimental HF Packet Nets

Name (Compatible NET)	Band	Center Frequency	Speed	Protocol	Usage/notes	Dial Frequency+Tone pairs
OH71018AX3 (NET40)	40M	7.101.8 MHz	300 Baud	AX.25/FX.25	Intrastate Forwarding	7.101.0 MHz USB, 800 Hz (Recommended) | 7.103.5 MHz LSB, 1700 Hz
OH71028AX3 (NET40)	40M	7.102.8 MHz	300 Baud	AX.25/FX.25	Intrastate Forwarding	7.101.0 MHz USB, 1800 Hz (Recommended) | 7.104.5 MHz LSB, 1700 Hz
OH71038IL3 (NET40)	40M	7.103.8 MHz	300 Baud	IL2P	Intrastate Forwarding	7.101.0 MHz USB, 2800 Hz
OH35965AX3 (NET80)	80M	3.597.5 MHz	300 Baud	AX.25/FX.25	Intrastate Forwarding	3.596.0 MHz USB, 500 Hz (Recommended) | 3.598.2 MHz LSB, 1700 Hz
OH35965AX3 (NET80)	80M	3.598.5 MHz	300 Baud	IL2P	Intrastate Forwarding	3.596.0 MHz USB, 1500 Hz

The following nets are intentionally too far away in frequency to be compatible with NET105/NET40/NET80. The frequencies/tones selected exist just inside the Part 97.221 Automatically controlled digital station (ACDS) band edges in an effort to minimize co-channel interference. The dial frequencies are outside the ACDS range, but the audio tones are inside the range. Remote/unattended stations may wish to permanently reside here while local/attended may choose to QSY here for forwarding only. If you choose to run ARDOP, VARA and/or Mercury HF modems on the proposed dial frequencies, it is imperative that the bandwidth is limited to 500 Hz. This preserves the 250 Hz buffer between AX.25/FX.25 space tone (1100 Hz) and IL2P mark tone (1900 Hz). More importantly, it keeps the VARA and/or Mercury HF modems within the ACDS subband to allow legal automatic operation.

Proposed/Experimental HF Mixed Mode Nets

Name	Band	Center Frequency	Speed	Protocol	Usage/notes	Dial Frequency+Tone pairs
OH104005AX3	30M	10.140.15 MHz	300 Baud	AX.25/FX.25	Intrastate Forwarding	10.139.15 MHz USB, 1000 Hz (Recommended) | 10.141.85 MHz LSB, 1700 Hz
OH1014065A5	30M	10.140.65 MHz	Various	ARDOP (500 Hz)	Intrastate Forwarding	10.139.15 MHz USB, 1500 Hz (Fixed)
OH1014065M5	30M	10.140.65 MHz	Various	Mercury (500 Hz)	Intrastate Forwarding	10.139.15 MHz USB, 1500 Hz (Fixed)
OH1014065V5	30M	10.140.65 MHz	Various	VARA (500 Hz)	Intrastate Forwarding	10.139.15 MHz USB, 1500 Hz (Fixed)
OH1014115IL3	30M	10.141.15 MHz	300 Baud	IL2P	Intrastate Forwarding	10.139.15 MHz USB, 2000 Hz
OH710015AX3	40M	7.100.15 MHz	300 Baud	AX.25/FX.25	Intrastate Forwarding	7.099.15 MHz USB, 1000 Hz (Recommended) | 7.101.85 MHz LSB, 1700 Hz
OH710065A5	40M	7.100.65 MHz	Various	ARDOP (500 Hz)	Intrastate Forwarding	7.099.15 MHz USB, 1500 Hz (Fixed)
OH710065M5	40M	7.100.65 MHz	Various	Mercury (500 Hz)	Intrastate Forwarding	7.099.15 MHz USB, 1500 Hz (Fixed)
OH710065V5	40M	7.100.65 MHz	Various	VARA HF (500 Hz)	Intrastate Forwarding	7.099.15 MHz USB, 1500 Hz (Fixed)
OH710015IL3	40M	7.101.15 MHz	300 Baud	IL2P	Intrastate Forwarding	7.099.15 MHz USB, 2000 Hz
OH359515AX3	80M	3.595.15 MHz	300 Baud	AX.25/FX.25	Intrastate Forwarding	3.594.15 MHz USB, 1000 Hz (Recommended) | 3.596.85 MHz LSB, 1700 Hz
OH359565A5	80M	3.595.65 MHz	Various	ARDOP (500Hz)	Intrastate Forwarding	3.594.15 MHz USB, 1500 Hz (Fixed)
OH359565M5	80M	3.595.65 MHz	Various	Mercury (500Hz)	Intrastate Forwarding	3.594.15 MHz USB, 1500 Hz (Fixed)
OH359565V5	80M	3.595.65 MHz	Various	VARA HF (500Hz)	Intrastate Forwarding	3.594.15 MHz USB, 1500 Hz (Fixed)
OH359615IL3	80M	3.596.05 MHz	300 Baud	IL2P	Intrastate Forwarding	3.594.15 MHz USB, 2000 Hz

NVIS Propogation

With the overarching goal of linking systems statewide, we must also employ antenna systems that favor NVIS type propagation. In general, this means horizontal (usually wire) antennas 1/8-1/4w wavelength above the ground or magnetic loops which are oriented vertically. For those interested in actual field strength tests, W8JI's NVIS page shows the height to performance numbers. For a quick reference, here are optimal antenna heights per band.

Band	Height
20M	8.25-16.5ft
30M	11.5-23ft
40M	16.5-33ft
80M	33-65ft

Conventional wisdom suggest NVIS primarily happens below about 10 MHz, though real world observation on 20m with a vertical magnetic loop at 3ft above the ground has yielded contacts well beyond groundwave, but far too short for lower angle skywave, leaving us well within NVIS ranges. More experimentation may be needed to test it's feasibility on modes which require stronger signals.