Irish Radio Amateurs first received permission to operate, experimentally on a secondary user basis, on specific spot frequencies located within the 5 MHz Band in October 2008. There were 3 spot frequencies allocated and one beacon frequency. More recently an additional 3 spot frequencies were issued. The modes of operation allowed are J3E (SSB), G1B (Phased Modulation - PSK and a maximum power level of 23dBW 200 watts. The spot frequencies are issued on a Secondary User, Non-Interference basis, the Primary users being Military and Aviation. A special application has to be made and this is renewed on an annual basis.
As radio amateurs are secondary users, there is no formal band plan for 5 MHz as each country has a different allocation. Strong debate on this subject is heard among UK operators but they basically do not call the shots as secondary users!
Operating on 5 MHz
Many tranceivers are able to transmit on 5MHz if they have the "Alaska Frequency" faciltiy and it is often just a case of opening or closing a link to gain access to the whole of the 5MHz band. it is essential to to set up the tranceiver correctly to ensure that the transmission only operates within the allocated 3KHz wide spot frequency. Upper side-band is the standard mode of voice operation. One should use a SSB filter no wider than 2.5KHz. The transmission should be set 1.5KHz below the centre of the channel frequency and with a typical voice band pass of 300Hz to 2800HZ the signal will just fit inside the channel allocation. See Fig 1.
Fig. 1. showing set up of transmitter for SSB operation
The table shown in Fig. 2 illustrates the centre frequency of the allocated channel, the appropriate carrier frequency, and the VFO dial frequency required. The dial frequency for the Clansman PRC 320 is also shown. It is probably best to place the dial frequencies into memory and select them as required but do remember to have USB programmed in as well. Note that the examples here are the Irish allocations which are comprised of only 6 channels.
Fig.2. Showing the relationship of carrier and dial frequency to the allocated spot frequencies
If setting up for PSK or other digital keyboarding Mode, the dial frequency should be set up the same as for USB voice and the PSK centre audio frequency should be at 1500Hz exactly - see Fig. 3. Operators should also
monitor USB voice to ensure that no interference is caused.
Fig. 3 setting up for PSK31 or other keyboard modes.
CW should be set up in exactly the same manner ensuring that the CW carrier is transmitted at the centre of the channel only. Likewise one should monitor USB voice to avoid interference with other users.
It should be noted that Amateur operators are Secondary users and should immediately vacate the channel if a Primary user should appear on channel. Irish Radio Amateurs are permitted to communicate with Licenced Radio operators only and do not have the facility or permission to enter into communication with Primary users of the band .
Typical Antennas for 5 MHz
The dipole shown in Fig. 4. is probably the easiest option for 5 MHz. by stringing it at a lower height e.g. a 1/4 wave or less above ground, one can take advantage of NVIS techniques. Placing it at a 1/2 wave or greater will take advantage of a lower angle of radiation and enable DX operation.
Fig. 4. Standard Dipole for 5 MHz.
Many other antennas such as the Inverted-Vee and better still the G4HOL antenna >> click here << strung just 200 ft above ground could be used. See the Technical Topics section of the Galway VHF Group Blogspot.
Propagation on 5MHz
Regular checks of the Chilton Ionogram will show the state of the bands during the day. Ideally the FoF2 should be around 5.5 - 5.6 considering that the optimum working Critical frequency should be 10% less. Checking the RAF Volmet on 5450 KHz and the Shannon Volmet on 5505KHz will give a good indication of the state of the 5 MHz band at any given time of day - that is whether more distant into the UK or just local in Ireland or both.
The 5 MHz band is an interesting "in between" band as it has both 80 metre and 40 metre properties. As the 80 metre band begins to fade out so the 5 MHz band becomes more useful until heading towards solar noon where the band slowly fades out in favour of the 40 metre band. As the 40 metre band opens more into Europe during the late afternoon so the 5MHz band begins to favour EI and UK operation being at is best at sunset. As the evening progresses towards midnight, the 5 MHz band begins to open up into Europe and becomes more "DXy". Quite predictable really.
WSPR Mode
Using WSPR (Weak Signal Propagation Reporter) it is possible to establish where the propagation is taking the signal to. In the case of Ireland we do not have the facility to actually transmit in this mode, due to frequency limitations, but it is possible to use the system on receive only. As it is in receive only it can be left running 24 hours a day. Here are some results of recent reception in Fig. 5. The Hidden secrets of 5 MHz revealed! Note what happens between 01:00 and 04:00 UTC - a rather nice opening to South Africa and South America.
The 5 MHz band is an interesting "in between" band as it has both 80 metre and 40 metre properties. As the 80 metre band begins to fade out so the 5 MHz band becomes more useful until heading towards solar noon where the band slowly fades out in favour of the 40 metre band. As the 40 metre band opens more into Europe during the late afternoon so the 5MHz band begins to favour EI and UK operation being at is best at sunset. As the evening progresses towards midnight, the 5 MHz band begins to open up into Europe and becomes more "DXy". Quite predictable really.
WSPR Mode
Using WSPR (Weak Signal Propagation Reporter) it is possible to establish where the propagation is taking the signal to. In the case of Ireland we do not have the facility to actually transmit in this mode, due to frequency limitations, but it is possible to use the system on receive only. As it is in receive only it can be left running 24 hours a day. Here are some results of recent reception in Fig. 5. The Hidden secrets of 5 MHz revealed! Note what happens between 01:00 and 04:00 UTC - a rather nice opening to South Africa and South America.
Fig. 5. Screen shots of WSPR Reception on 5 MHz at 01:00 - 04:08 UTC
Regular nets are held at sunrise and sunset around 5398.5 KHz and the RSGB News may be heard transmitted on 5 MHz on Sunday afternoons at 4pm.
To get around the problem of many who may not have applied for the 5 MHz allocation it is possible to hold a cross-band QSO where you, the 5 MHz licencee, transmit on the 5 MHz frequency and the other station transmits on a 40 or 80 metre frequency. In the case of countries with allocations outside of the Irish Allocation it is also possible to transmit on an Irish frequency allocation and receive on the other operators frequency and example - EA7JVZ set up a QSO as follows for the UK/Irish ops:
Transmit Frequency: 5278.5 kHz USB (UK/Ireland)
Receive Frequency: 5428.5 kHz USB (Spanish TX Frequency)
Unfortunately the Spanish 5MHz allocation does not coincide with the UK or Irish system at present.
The future of 5 MHz frequency allocations will be decided at the WARC 2015 conference where a more unilateral allocation on 5 MHz may be possible. Naturally there are a number of Administrations/Primary users who do not want to give up their possession of the 5MHz spectrum.
