Engineers Without Borders / Aptivate Field Communications Course Cambridge, 8 March 2008 File Contents:  Licensing (dur 10 mins, 10 slides);  HF Equipment (dur 10 mins, 8 slides);  VHF Equipment (dur 10 mins, 8 slides) Prepared for Cambridge University Wireless Society by Dominic Smith M0BLF

Licensing

Overview  Tampere Convention  Emergency Communications in the UK  UK Licence Limitations  International Licensing

Licensing :: Tampere Convention  ‘Tampere Convention on the Provision of Telecommunication Resources for Disaster Mitigation and Relief Operations’  In force since 8 January  Countries can request assistance from other countries in times of disaster, and other countries can provide operators and equipment.  Grants operators immunity from arrest, customs duties on equipment etc. to the extent permitted by national law. Key points

Licensing :: Tampere Convention  Ownership of equipment unaffected.  Provision of assistance may be dependent on payment.  Expects signatories to reduce or remove regulatory barriers on eg. import/export of equipment, use of frequencies, movement of operators, administration delays in case of disasters.  More info on how this affects amateur radio ops: Key points

Licensing :: EmComms in the UK  Radio Amateurs’ Emergency Network, founded 1953  Volunteers from the amateur community  Experienced in message handling at major incidents (eg. Lockerbie) and public events (eg. London Marathon)  BUT: despite problems with comms highlighted in 7/7 report, Raynet and UK Radio Amateurs are not currently in official government emergency plans.  Similar groups in the US regularly assist after hurricanes and other disasters (eg. New Orleans). Raynet

Licensing :: UK  Amateurs are specifically permitted to pass messages for emergency organisations: UK Amateur Radio Licence 1(2) The Licensee may use or permit the use of the Radio Equipment by a member of a User Service during any operation conducted by a User Service or during any exercise relating to such an operation in each case for the purpose of sending Messages on behalf of the User Service. 1(3) The Licensee may use the Radio Equipment to assist with communications in times of disaster or national or international emergency.

Licensing :: UK  These ‘Responders’ include Police, Fire, Ambulance, NHS trusts, County and City Councils, Utility Companies, Health & Safety Executive, a Secretary of State, Environment Agency, Railway Companies etc. User Services "User Service" means the British Red Cross, St John Ambulance, the St Andrew's Ambulance Association, the Women’s Royal Voluntary Service, the Salvation Army, any Government Department, any ‘Category 1’ responder, and any Category 2 responder as defined in the Civil Contingencies Act 2004

Licensing :: UK  Encryption not permitted.  Now allowed remote operation (eg controlling transmitter via internet) if the link is secure.  Some frequencies assigned in voluntary bandplan as preferential for emergency use.  Full and Intermediate licensees can build their own equipment. Other points

Licensing :: International  UK full licensees covered by CEPT TR/61-01  International agreement allowing operation in over 30 countries (mainly Europe but also USA, Canada, Australia).  Having a US callsign can give additional reciprocal privileges especially in Caribbean / South America.  In some places more difficult to get a licence. Reciprocal Agreements

Licensing :: International  Power and some frequency allocations vary internationally.  Under UK licence, you can listen to a foreign amateur outside of the UK spectrum, provided you transmit within the UK spectrum.  Some frequency allocations where amateur radio is the primary user in the UK can be secondary overseas (so you might have to put up with interference). Emergency Communications

HF Equipment

Overview  Propagation at HF  Equipment used

HF Equipment :: Propagation The Ionosphere  Below approx. 30MHz, waves refract in the ionosphere and come back down to Earth  The earth can then reflect the wave back up for another go.  So - HF radio waves can bounce around the world.  But it depends on various factors.  Each HF band will only support propagation to a particular place at certain times when it is said to be “open”.

HF Equipment :: Propagation Some characteristics and factors  1.8 MHz: best during long winter nights for UK and Europe  3.5 MHz: for UK by day and Europe by night  7 MHz: principally for Europe  14MHz: Pacific in the morning, US in the afternoon. Not much at night  21MHz: Different places worldwide at different times, except during low sunspot activity  28MHz: worldwide by day only during high sunspot activity

HF Equipment :: Propagation Near the transmitter  A ground-wave allows reception in immediate area  But there is a ‘skip zone’ where you are not heard between the end of the ground-wave and the first hop from the ionosphere. Therefore depends on angle of incidence.  This means you might not be heard by a station on the same frequency, whom you can hear. Interference potential.

HF Equipment :: Propagation Natural Interference  Propagation also means HF can be very noisy from natural interference. Eg:  Fading  Aurora  Static crashes

HF Equipment :: Antenna Antenna  Size of antenna related to wavelength.  Low frequencies have long wavelength, so antennas tend to be very big. Often impractical.  Can get good results with wire stretched from a temporary fibreglass mast.

HF Equipment :: Modes Transmission modes  Aimed at low-bandwidth rather than fidelity. SSB preferred to AM  Some packet data links but traditionally very slow <1000 baud because of low signal:noise  Some promising experiments now with digital voice using FEC.  Amateur HF is not channelised, so additionally get ‘splatter’ from adjacent stations.

VHF Equipment

Overview  Propagation at VHF  Equipment used

VHF Equipment :: Propagation Point-to-Point  The range of a signal >30MHz depends on the antenna height, a clear path, frequency and transmitter power.  VHF/UHF range is generally little more than line of sight.  Line of sight at VHF/UHF is a little further than the horizon because of refraction in the atmosphere. Hills and buildings cause path loss.  At VHF and UHF (ie 30MHz+), hills cause shadows.  Higher antennas are better than higher power - they work on receive as well.

VHF Equipment :: Propagation Other phenomena  ‘Sporadic E’ (E s ) occurs when ‘clouds’ in the E-layer in the ionosphere becomes ionised. (At HF refraction is in the higher F-layer).  Unknown how these ‘clouds’ form, and they are sporadic.  Tend to occur in the summer months, and also a small peak in mid-winter.  Can allow VHF communication over 1000 miles.  Rarely affects above 150MHz.

VHF Equipment :: Propagation Other phenomena  Tropospheric ducting occurs when a temperature inversion forms just above the Earth’s surface.  A ‘duct’ can form along the inversion, along which VHF waves encounter low attenuation.  Only happens a few days per year, and allows communication over 500 miles, often in a specific direction.

VHF Equipment :: Propagation Increasing range  A network of repeater stations (often on tops of hills) relay transmissions in real-time, thereby extending range.  Many of these are now linked to the internet (VoIP gateway to another repeater or user’s computer).  New D-STAR digital voice repeaters with gateway permit ‘dialling-up’ another amateur by callsign, without needing to know what repeater they are listening to.

VHF Equipment :: Equipment Bands  Main ones are 144MHz and 430MHz.  Also have an allocation at 50MHz but unreliable propagation.  Microwave allocations often experimental but also fast-scan television.  Some SSB, but mainly channelised FM.  Faster data links.  Less susceptible to interference.

VHF Equipment :: Equipment Equipment  Antenna size much more practical – even beams.  But antenna polarization important.  Handheld and mobile equipment.