Enriched air, containing over 21% oxygen (commonly 32% or 36%), extends dive time by increasing no-decompression limits, but it reduces the maximum safe diving depth.

The International Standard Atmosphere (ISA) is a model of the pressure exerted by the Earth's atmosphere. At sea level, the pressure of a standard atmosphere is:

Instead of hPa, divers measure pressure in atmospheres. One atmosphere equals 1013.25 hPa. At 30 metres underwater, you'd feel 4 atmospheres of pressure: 3 from the water and 1 from the air above.

Air pressure is made up of about 21% oxygen and 79% nitrogen. This means the oxygen itself exerts 0.21 atmospheres of pressure, and the nitrogen exerts 0.79 atmospheres at the surface. When you dive to 20 meters, the total pressure increases to three atmospheres. Because of this, the individual pressures of the gases also triple: oxygen becomes 0.63 atmospheres, and nitrogen becomes 2.37 atmospheres.

Using enriched air increases the amount of oxygen and reduces the amount of nitrogen we breathe:

We evolved to breathe air at 1 atmosphere of pressure. Breathing at higher pressures can cause decompression sickness, oxygen toxicity, and nitrogen narcosis.

Decompression Sickness​

When diving, nitrogen from the air we breathe dissolves into our body until it reaches the same pressure as the air. Because nitrogen is inert, this buildup isn't harmful while underwater. However, during ascent, the pressure decreases, and the dissolved nitrogen needs to be released to regain equilibrium. If this release happens too quickly, nitrogen bubbles can form in the body, leading to decompression sickness.

At 10 meters deep, where the pressure is 2 atmospheres, the nitrogen partial pressure doubles to 1.58 atmospheres. This means your body absorbs twice as much nitrogen as at the surface, once it reaches equilibrium. By using breathing gas mixtures with less nitrogen, we reduce the amount absorbed. Dive computers and specialized dive tables calculate no-decompression limits based on this reduced nitrogen absorption.

Unlike nitrogen, oxygen doesn't cause decompression sickness because our bodies actively use it. Our physiology regulates the partial pressure of oxygen delivered to our cells. This system functions effectively within the partial pressure ranges experienced during recreational diving. As a result, only inert gases contribute to decompression sickness.

Oxygen Toxicity​

Too much oxygen can lead to pulmonary toxicity or central nervous toxicity.

Pulmonary Toxicity​

Breathing oxygen at high partial pressures for extended periods can irritate the lungs, causing a burning sensation and cough. The time required for these symptoms to develop is significantly longer than recreational dive durations.

Central Nervous System Toxicity​

Central Nervous System (CNS) toxicity can have a sudden and unpredictable onset, leading to seizures and unconsciousness. A diver experiencing CNS toxicity underwater would almost certainly drown. There is ongoing discussion about safe oxygen partial pressure limits, with conservative estimates at 1.4 atmospheres and a generally accepted upper limit of 1.6 atmospheres.

Using standard air (21% oxygen), to reach a 1.4 atmospheres oxygen partial pressure, you would have to dive to 6.6 atmospheres (56.6 metres). This is beyond recreational diving limits. Breathing pure oxygen would result in reaching the 1.4 atmospheres danger zone at just 4 metres deep. This is why breathing gas mixtures must always include inert gases to reduce the oxygen concentration.

The safe maximum depth must be calculated for every dive using exact percentage of oxygen in your mixture. The maximum depth in atmospheres can be calculated by dividing the 1.4 atmosphere limit by the partial pressure of oxygen.

Nitrogen Narcosis​

Nitrogen narcosis can cause impaired judgment and intoxication-like symptoms, leading to risky behaviors such as disregarding decompression stops or depth limits. These effects rapidly subside upon ascending to a shallower depth. Most divers don't experience noticeable narcosis shallower than 30 metres.

Air dives are more susceptible to nitrogen narcosis. Using an enriched air mixture, with a higher oxygen and lower nitrogen content, like EANx32, reduces the risk. For example, at 10 metres (2 atmospheres), the partial pressure of nitrogen on EANx32 is 1.36 atmospheres, compared to 1.58 atmospheres on air.

Pre-dive Checks​

Oxygen content will vary between cylinders due to production differences. You must check your cylinder's oxygen percentage with an oxygen meter before diving. Input the measured percentage into your dive computer for accurate no-decompression and maximum depth calculations.

This information should be written on your cylinder to show that the checks have been completed:

VHF and HF radios can transmit messages to all stations within range. VHF (Very High Frequency) radio provides short-range communication suitable for coastal areas. HF (High Frequency) radio enables communication over much greater distances, often spanning entire continents.

Satellite phones provide private, point-to-point communication, enabling direct calls to individuals globally.

Emergency Position-indicating Radio-beacons (EPIRBs) are designed to automatically transmit distress signals to alert rescue services worldwide.

Legislation​

The Australian Communications and Media Authority (ACMA) regulates Australia's radio communications and telecommunications under the Radio Communications Act 1992 and other legislation.

The Radio Communications Act regulates the use of radio frequencies. Very High Frequency (VHF) equipment is licensed under the General Maritime Ship Station class, requiring no individual applications or fees. Each piece of High Frequency (HF) equipment requires an individual station license issued by ACMA.

You must hold the necessary qualifications to operate VHF or HF marine radio equipment:

• To operate a station with VHF equipment, you must have a Short Range Operator Certificate of Proficiency (SROCP)

• To operate a station with HF equipment, you must have a Long Range Operator Certificate of Proficiency (LROCP)

The radio is under the control of the vessel's master, skipper, or safety officer.

Radio Waves​

A hertz (Hz) is a unit of frequency that measures how often something happens per second. For example, if something vibrates 10 times per second, it has a frequency of 10 hertz.

The electromagnetic spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.

The electromagnetic spectrum is organized by frequency, radio waves have lowest frequencies in the electromagnetic spectrum. The radio spectrum includes frequencies from 3 Hz to 3,000,000,000,000 Hz (3,000 GHz).

The radio spectrum is allocated by the International Telecommunication Union (ITU) for different radio technologies. Marine radio is allocated to frequencies in the Very High Frequency (VHF) and High Frequency (HF) spectrum.

• VHF signals travel as ground waves in a straight line and can only reach as far as the line of sight between antennas. VHF has a range of about 3 nm.
• HF signals travel as sky waves bouncing off the ionosphere increasing their range to 100 - 400 nm.

Radio Equipment​

Transmitter and Receiver​

A transmitter generates radio waves by converting electrical signals into electromagnetic radiation. This radiation is then emitted through an antenna. A receiver is a device that captures these radio waves and converts them back into electrical signals. More powerful transmitters can send signals further. Very High Frequency (VHF) radios generally capped at 25 watts.

To reduce background noise, VHF radios feature a squelch control. This automatically mutes the speaker when no radio signal is being received. A comparable function, termed 'mute,' serves the same purpose on High Frequency (HF) radios.

Antenna​

A VHF antenna, typically a short vertical whip or rod, is significantly smaller and simpler in design compared to a larger HF antenna.

An antenna tuning unit (ATU) on an HF radio improves power transfer by matching the impedance of the radio and its antenna. Impedance is the opposition to the flow of energy in the antenna. An antenna's impedance is different at different frequencies.

Power Supply​

Voltage (V) is how strong the electrical current is. Ampere-Hours (Ah) is how much electricity your battery can store

• Connecting batteries in series increases the voltage.
• Connecting batteries in parallel increases the ampere hours.

Fuses are safety devices that protect electrical circuits from excessive current. If your device draws too much current, the fuse will interrupt the flow of electricity to prevent overheating and fire. You should only replace a fuse with the exact one recommended by the manufacturer.

Coast Stations​

Australia maintains two High Frequency (HF) coast stations: Wiluna in Western Australia for the west coast and Charleville in Queensland for the east coast. Both stations are centrally managed by the Rescue Coordination Centre (RCC) in Canberra, operating under the call-sign "RCC Australia".

Services provided include:

• Continuous watch of HF distress signals
• Continuous watch on HF DSC distress signals
• HF Weather forecasts and warnings

Limited Coast Stations​

States and territories operate Very High Frequency (VHF) limited coast stations, identified by the call-sign "Marine Radio" followed by the state's name.

Services provided include:

• Watch of VHF distress signals
• Watch on VHF DSC distress signals
• Communications relating to the safety and movements of vessels in their area (for example Logging on and off)

Radio Calls and Messages​

Radio calls are short phrases used to initiate a communication. Radio messages are the content of the message being communicated.

Your call sign or identification must be included with every transmission. The receiving station (the one being called) has the primary authority to dictate how the communication will proceed.

Digital Selective Calling​

Digital Selective Calling (DSC) allows you to address your call to a specific radio and suggest a working frequency before switching to a voice channel to send your message. DSC calls are more reliable than voice communication, especially in noisy or weak signal conditions.

Each radio equipped with DSC has a unique Maritime Mobile Service Identity (MMSI) number, similar to a phone number. In an emergency, a DSC distress call can be sent with the push of a button, automatically including the vessel's MMSI, position (if connected to a GPS), and the nature of the distress.

An MMSI is a nine-digit number. The first three digits are a country code, and the remaining six digits are a unique ID for that vessel.

Numbers may be added to the beginning of the MMSI:

When you receive a DSC call, determine if it is a distress or routine call. Distress alerts take highest priority.

• Distress Call: Listen on channel 16 kHz for further information. The alert will usually be followed by a voice message explaining the situation.
• Routine Call: Switch to the working channel indicated in the DSC call to communicate with the calling vessel.

Routine Calls and Messages​

To initiate a radio call:

1. Determine the correct frequency: Ensure you are calling the station on a frequency they are actively monitoring. For Very High Frequency (VHF) this will be channel 16 for High Frequency (HF) it will be a distress, urgency or safety channel.

2. Check for clear frequency: Before transmitting, listen to ensure the frequency is not in use by others.

3. Follow the correct format: Structure your call as follows:

   • Call the station. State the call sign or identification of the station you are contacting.
   • Identify yourself. Provide your own call sign or identification.
   • State your position. Indicate your location (e.g. distance and bearing).
   • Describe your request. State the nature of your message.
   • Suggest a working frequency. Propose a frequency for the actual message exchange.
   • End with "Over". This indicates that you expect a response from the station.

Example call:

New South Wales Marine Radio, this is sailing boat Illusion inside Sydney Heads with logon details. Suggest channel 73. Over.

You have established communication once the station being called responds. You can now send the content of your message including your identity.

Example message:

Illusion, registration alpha bravo charlie one two three november, inside Sydney Heads traveling North to Broken Bay arriving 1500. Three people on board. Mobile number: 0412 345 678. Over.

Distress Calls and Messages​

Distress calls may be directed to a specific station or broadcast to all stations. Mayday is the most urgent, followed by Pan-Pan, and then Securite. Mayday has the highest priority and must be given immediate attention, even if other transmissions are in progress.

• Mayday. Used when there is an immediate threat to life.
• Pan-Pan. Used when there is an urgent situation that does not immediately threaten life or threatens property.
• Securite. Used to transmit important navigational or safety information.

Distress calls follow the same format as routine calls, but instead of naming the station, you begin with "Mayday," "Pan-Pan," or "Securite" repeated three times.

Example call:

Mayday, Mayday, Mayday. This is sailing boat Illusion, Illusion, Illusion.

No response is expected after making a mayday call, broadcast your message after a brief pause. All other stations must stop transmitting.

Example message:

Mayday Illusion. Three nautical miles East of Barrenjoey. Sinking. Three people on board. EPIRB activated. Over.

Emergency Position-indicating Radio-beacons​

How long should the 406 MHz EPIRB be capable of transmitting? What signal is transmitted by a 406 MHz EPIRB? When may an activated EPIRB be switched off? How can an EPIRB be tested? Accidental activations

What type of orbit is used by the CASPAS-SARSAT LEO satellites? What type of orbit is used by the CASPAS-SARSAT GEO satellites? What is the viewing footprint of the CASPAS-SARSAT satellites? Duration of orbits

Central Coast​

Ourimbah State Forest​

Topo Map: Wyong 9131-2N

Follow the well-maintained Red Hill Road between Kulnura and Wyong. The busy Central Coast Mountain Bike Club trails are at the Wyong end. Middle Ridge Road South to Palmdale is closed to prevent illegal dumping. Many fun diversions, mostly leading nowhere.

Watagans National Park​

Topo Map: Wyong 9131-2N Dooralong 9131-1S Morisset 9131-1N Quorrobolong 9132-2S

Watagan Forest Road starts at Wyong State Forest near Jilliby and tracks North through the Jilliby State Conservation Area and Olney State Forest before entering Watagans National Park. Watagan Forest Road is closed at the North near Quorrobolong due to a landslip. Exit via Heaton Road to Awaba near the Awaba Mountain Bike Trails.

Lithgow​

Lisdale State Forest​

Topo Map: Lithgow 8931-3S

Heading East from Rydal Cemetery leads to a steep, well-graded descent followed by a very steep, awkward climb. Cemetery Road leads North through the Central Tablelands Mountain Bike Club's trails then easy riding along the railway, park boundary or through the plantation.

Marrangaroo National Park​

Topo Map: Lithgow 8931-3S

Enter Sugarmans Road from the Great Western Highway at the North of the Park. Track South crossing the Coxs River. Mount Walker is closed to traffic for development of the Lake Lyell Pumped Hydro Project, but is accessible by foot. Continuing to the east leads to a locked gate where Mount Walker road leaves the national Park onto private property. Mount Walker Road becomes extreme further South to the point at Lake Lyell. Station Road is impassable at the Coxs River crossing. Exit back via Sugarmans Road.

Rydal 4WD Area​

Topo Map: Lithgow 8931-3S

Rydal 4WD Area is found at the Eastern end of Bloody Cutting Road South of Rydal. Many steep, rocky sections most with alternative escapes back to Bloody Cutting Road. Unavoidable steep climbs to the North to enter Lisdale Satate Forest.

The final product:

• Plex Media Server is a a central streaming hub for all your media files (movies, TV shows, music etc).

• VPN provides a secure and encrypted connection to usenet.

• Lidarr, Radarr and Sonarr monitor usnet to download new movie, TV show or music releases.

• Prowlarr manages the usenet indexer.

• Sabnzdb manages the usenet downloads.

Docker Engine​

Learn how to install Docker Engine.

Remember to carry out the post-installation steps if installing on Linux.

Verify that you can run docker commands without sudo:

docker run hello-world

Docker Compose​

Docker Compose is a tool that lets you define and run multi-container Docker applications with a single command.

Create a file called compose.yaml in your project directory.

You define individual software components as services. Services interact with each other through networks. Volumes allow services to store and share data, effectively mounting external filesystems.

Plex Media Server​

services:
  plex:
    # The package that includes everything you need to run Plex.
    image: lscr.io/linuxserver/plex:latest

    # The name of your service
    container_name: plex

    # Set your service's network mode.
    # "host" gives your service direct access to your server's network.
    network_mode: host

    # Define your service's environment variables.
    environment:
      - PUID=1000 # UserID
      - PGID=1000 # GroupID
      - TZ=Etc/UTC # Specify a timezone
      - VERSION=docker # Whether to update plex or not

    # Define host paths accessible to your service. host/path:docker/path
    volumes:
      - /docker/appdata/plex:/config # Plex configuration data
      - /data:/data # Media

Add your timezone from the list of TZ Identifiers.

Start Plex by running docker compose up

Plex can be found at <your-ip>:32400/web

VPN​

Gluetun helps you set up a VPN connection within Docker. It supports various VPN providers.

Usenet provider NEWSHOSTING includes a VPN.

gluetun:
  image: qmcgaw/gluetun

  container_name: gluetun

  hostname: gluetun

  # Add container capabilities.
  cap_add:
    - NET_ADMIN # Allow this container to configure your service's network.

  # Device mappings
  devices:
    - /dev/net/tun # See https://github.com/qdm12/gluetun-wiki/blob/main/errors/tun.md

  environment:
    # See https://github.com/qdm12/gluetun
    - VPN_SERVICE_PROVIDER=
    - OPENVPN_USER=
    - OPENVPN_PASSWORD=

  ports:
    - 8686:8686 # lidarr
    - 7878:7878 # radarr
    - 8989:8989 # sonarr

  restart: unless-stopped

Start your VPN by running docker compose up

Lidarr, Radarr and Sonarr​

Add the Lidarr, Radarr and Sonarr containers following the same pattern as for Plex.

lidarr:
  image: lscr.io/linuxserver/lidarr:latest
  container_name: lidarr
  environment:
    - PUID=1000
    - PGID=1000
    - TZ=Etc/UTC
  volumes:
    - /docker/appdata/lidarr:/config
    - /data:/data
  network_mode: "service:gluetun" # Connect through VPN
  restart: unless-stopped

radarr:
  image: lscr.io/linuxserver/radarr:latest
  container_name: radarr
  environment:
    - PUID=1000
    - PGID=1000
    - TZ=Etc/UTC
  volumes:
    - /docker/appdata/radarr:/config
    - /data:/data
  network_mode: "service:gluetun"
  restart: unless-stopped

sonarr:
  image: lscr.io/linuxserver/sonarr:latest
  container_name: sonarr
  environment:
    - PUID=1000
    - PGID=1000
    - TZ=Etc/UTC
  volumes:
    - /docker/appdata/sonarr:/config
    - /data:/data
  network_mode: "service:gluetun"
  restart: unless-stopped

Start your Lidarr, Radarr and Sonarr by running docker compose up

• Lidarr can be found at <your-ip>:8686
• Radarr can be found at <your-ip>:7878
• Sonarr can be found at <your-ip>:8989