Engineers Without Borders / AptivateField Communications CourseCambridge, 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 m0blf@m0blf.org.uk

Licensing

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 2005.

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:

http://www.iaru.org/emergency/tc-hams.html

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 :: UKLicensing :: 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

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 :: PropagationHF 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

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’ (Es) 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.