Exercise Blue Ham

RAFAC logo


Exercise Blue Ham is run two or three times a year by the RAF Air Cadets (RAFAC) on the shared allocation of the 5 MHz band to facilitate their on-going training in the usage of radio. There may also be other cadets organisations taking part: Army Cadet Force (ACF), Sea Cadet Corps (SCC), and the Combined Cadet Force (CCF). The exercises allow the cadets to experience operating on HF, with all the vagaries of Near Vertical Incident Skywave, European DX, QRN, and the fun of pile-ups. Many of the cadet stations encourage their youngsters to embrace the wonderful world of Amateur Radio (and to gain their licence), so it is important that we take part in the exercise to encourage their on-going training, and to highlight how Radio Amateurs can work with the military, especially at times of national emergencies.

Taking part

Please see the External link  Alpha Charlie website for details of the exercises.

The 5 MHz band is only available to UK Radio Amateurs with a Full licence. You should operate in accordance with the licence restrictions and within the designated band-plan. Receiving a BlueHam station outside of the UK Radio Amateur band-plan does not give you permission to contact them. If you transmit out-of-band: the Men-in-Black will take you from your home in the middle of the night to a secret base where you will be strapped to a chair in a sound-proof room and made to watch every episode of Coronation Street. Probably!

International Radio Amateurs reading this page: please check to ensure your licence allows you to operate on the 5 MHz band. You must operate within the limitations of your licence and your country's agreed band-plan. The United Kingdom's 5 MHz band-plan operates over a larger area than WRC-15, and you may not have the ability to transmit on the same frequencies.

The RAF Air Cadet stations will call "alpha charlie, alpha charlie, alpha charlie, this is...", followed by their assigned call-sign. This will take the form of MRExxx; e.g. MRE21, MRE77A, MRE10B. Alpha Charlie stands for "any call-signs", and this form of call only applies to cadet stations. Radio Amateurs wishing to call for contacts during exercises should continue to call CQ. Radio Amateurs should not call alpha-charlie! You may wish to call "cq blueham ... listening for any cadet stations".

Please remember to use the NATO phonetics (as anything else is really annoying!). All voice communications on 5 MHz use Upper Side Band. Lower Side Band is not to be used on 5 MHz. It would be preferable to avoid using AM during BlueHam weekends. Please check the quality of your transmissions: over-driving your linear and transmitting with a distorted signal is very hard to read; as is an echo from leaving an SDR running in the background.

Please be patient and give the cadets time to answer your reply to their alpha-charlie call. This could be the first time operating on HF and it is quite scary to have lots of voices yelling their call-signs at once. Remember this is an exercise, not a contest! The details they will exchange with you are listed on the Alpha Charlie website. The cadets can learn a lot from the different transceivers and aerials used by different Radio Amateur stations, especially when they reference it to the equipment and aerials they are using. And it might be enjoyable to learn what the weather is doing in your part of the world!

Maidenhead Locator note: The cadet stations may be operating from active military sites within the United Kingdom. Whilst we (as UK residents) know where they are, and most are sign-posted on the road, the cadets will not give out an exact location or an exact Maidenhead Locator. Do not be surprised if a locator appears in the North Sea!

You may hear two cadet stations calling "alpha charlie" on the same frequency. Working both stations will be a challenge for everyone and a test of listening skills. Be clear and concise, and try not to stomp on other people's transmissions!


My tips for logging calls: Listen and make a note of the cadet station's call-sign, locator, and any other details; then leave a space on your notepad. I note down the frequency the cadet station is currently operating on, then write the UTC time against that when I have worked them. When they move frequency, I already have their details noted, and only need add the new frequency and time.

Working the same cadet station on a different frequency counts as a separate contact. This applies to both Saturday and Sunday. i.e. MRE99 worked on 5.313 at 12:00 UTC on Saturday is 1 contact for Saturday. MRE99 worked on 5.4305 at 14:10 UTC on Saturday is 2 contacts for that station. MRE99 worked on 5.313 at 11:00 UTC on Sunday is 1 contact for Sunday.

If you manage more than 10 contacts over the weekend, you can send your log file in ADIF format to the BlueHam team via email. You may need to remind them if you have not received your certificate after a few weeks. They have a lot to process!


The following lowest USB dial frequencies (in MHz) are most likely to be used, and should prevent UK Radio Amateurs from operating out of band:

  • 5.276
  • 5.2785
  • 5.2985
  • 5.301
  • 5.304
  • 5.317
  • 5.320
  • 5.335
  • 5.354 (WRC-15)
  • 5.363 (Partly in WRC-15)
  • 5.3665 (Digital Mode: Olivia 16/500)
  • 5.3715 (Digital Mode: BPSK 31)
  • 5.379
  • 5.395
  • 5.3985
  • 5.4035


March 2019 My thanks to Valerie G6XDK for allowing me to use her out-of-town QTH for a ~30 dB decrease in QRM noise levels and the 35 contacts it allowed me to make.

March 2019 BlueHam certificate
Click on the image to load a larger version (in a new window).

June 2019 My thanks to Sandra Round of the (former) Old Bull Pub in Gamlingay, South Cambridgeshire, for allowing me to set-up my dipole aerial in the back garden (more of a field by modern housing standards). Operating /P for the first time, several major challenges included: setting up the aerial for the first time with the wind trying to blow it over; trying to work through the entire weekend with a throat-infection; and trying to work through Saturday with the crashing of QRN from a large number of thunder storms spread across Europe. Despite the QRN, the QRM levels were low enough to successfully operate - even working MRE34B in Scotland. QRM levels could only be lower by cutting the power to the village...

The resonant 5 MHz band dipole set-up (on Friday) with a 10 metre extending mast, a concrete lump to steady the base, guy lines, and the wire ends supported with two 10 metre carbon-fibre "roach poles", both held up with guy lines (only one side visible):

June 2019 BlueHam aerial
Click on the image to load a larger version (in a new window).

The aerial ended up on a North-East - South-West (ish) orientation due to the available open ground. The purchase of some suitable lines and equipment may see two trees used as sky-hooks for a future installation on an East-West (ish) layout.

Detail of the left-most support. Screw-in ties for dogs/tents proved useful as ground anchors. The roach-pole is held in place with a Marquee/Parasol ground spike. Yellow 3 mm nylon line is used for the guy lines so they are visible to everyone walking around the area.

June 2019 BlueHam aerial
Click on the image to load a larger version (in a new window).

An on-site mobile home provided a very useful operating "shack" sheltering myself (and visitors) from the passing June showers. Yes, the sticky note is to remind me to use the Maidenhead Locator for that area and not give-out the one for my QTH!

June 2019 BlueHam shack
Click on the image to load a larger version (in a new window).

On Sunday, I was pleased to be able to help G3ATC to provide Jamie, Jade, Asad, and Megan with some HF operating experience on their Amateur Radio Foundation Licence practical training. I hope they are proudly sporting M7 callsigns now!

June 2019 BlueHam certificate
Click on the image to load a larger version (in a new window).

June 2020 My thanks again to Sandra Round of the (former) Old Bull Pub in Gamlingay, South Cambridgeshire, for allowing me to set-up my dipole aerial in the back garden (more of a field by modern housing standards). Operating /P again in a low-noise rural area saw my helpers and I rained on whilst setting up on Friday. In a repeat of last year's weather, Saturday hit us with rain, wind, hail, thunderstorms, and major QRN. At least Sunday was a little quieter! Overall, a successful weekend despite the lack of cadets due to the SARS-Cov2 lockdown.

June 2020 BlueHam certificate
Click on the image to load a larger version (in a new window).

Page updated: 8th June 2020

Home  |  Tips  |  Linux  |  fldigi  |  APRS  |  QSSTV  |  WSJT-X  |  Blue Ham  |  Projects  |  Repairs  |  Downloads  |  Links