Operation Manna and Operation Chowhound were humanitarian food drops to relieve the famine in Holland behind Nazi lines late in World War two.
The Special Event.
Teams of Radio Amateurs from around the world are coming together on April 25th, 26th, and 27th 2025 to put on special event stations from interesting places to commemorate operation Manna and Chowhound.
Please use this website and the internet to learn a little about the terrible famine in the Netherlands at the end of WW2 and operation Manna / Chowhound that some experts believe saved four Million lives.
We think that this Operation is very important to commemorate not only to remember the thousands of people who died, those who were saved, and their saviours, but also to learn lessons for the future.
A great chance to practice your radio skills and have some interesting conversations with our teams and other amateur radio operators and Youth groups around the World. Maybe that person you talk to in Holland would never have been born were it not for operation Manna / Chowhound.
There will be people on air with personal stories about their own family that you will find incredible.
On the Stations page you will be able to find the current HF frequency of our stations and links to Web SDR sites. A really interesting thing to do is open a Web SDR and hear how well a particular station is being heard in a certain Country.
If you are a Computer Science student maybe you would like to look at some of the software being used for this event and discuss it with its developer Rose 2E0RXO who will be on air. Details to come.
Perhaps you could create a KML file of the locations of our stations and your School or Organisation location plus other participating groups and stations maybe as many airfields and drop zones as you can find with your research, or something else tech related ?
If you send us things during the event we will publish them here be that tech stuff artwork poetry , photos or anything else suitable .( If sending photos please include permissions if relevant.)
A Very Brief Guide to Amateur radio.
Amateur Radio is about self training and experimentation with radio and electronics as a non business recreational activity. Although it does have its uses in times of emergency when normal communications could be compromised.
Frequency and Wavelength Wavelength is the distance from the peak of a radio wave to the peak of the next and is measured in normal Metric Measurements. Frequency is the number of times that wave happens per second and is measured in Hertz. A typical Music station on your basic FM radio could have a Wavelength of about 3M and about 98,000,000 Hertz per second. As this number is a bit long we tend to quote radio frequencies in Megahertz or MHz. You can see from this the relationship and that as a frequency rises the Wavelength must get smaller.
Frequencies commonly used in amateur radio.
HF or High Frequency = 3MHz to 30 MHZ. These are the frequencies with the ability to bounce off of the Ionosphere and return to Earth making around the World communication possible without anymore infrastructure than a pair of radios and antennas.
VHF or Very High Frequency 30MHz to 300MHz local communication.
UHF or Ultra High Frequency 300MHz to 3000 MHz local communication.
The radio waves are modulated in various ways to carry the required data be that FM Frequency Modulation, AM Amplitude modulation, Single Side Band modulation and so on.
Inside the radio
In an Analogue Radio on the Transmission side there are four basic stages.
The Audio stage this takes and amplifies the signal coming in from the microphone. The Frequency Generator or Oscillator this creates the carrier signal at the correct frequency. The Modulator this mixes the carrier signal and the audio signal from the audio stage together. RF amplifier this boosts the signal and feeds it to the antenna via a feeder that is often coax or ladder line.
An Analogue Radio on the Receiver side has three basic stages.
The tuning / RF Amplifier this stage tunes the receiver to the correct frequency and amplifies the weak received signal. The Demodulator this extracts the original audio by separating it from the modulated signal the radio has received. Audio amplifier this stage amplifies the weak audio signal from the demodulator and passes it to the speaker.
An SDR Radio or Software Defined radio on the Transmission side.
Incoming signals from the Microphone are converted from analogue to digital. The modulated radio signals are created using software. The resulting signal is converted from digital to analogue then amplified and fed to an antenna.
An SRD Radio or Software Defined Radio on the Receive side.
Incoming signals are converted from analogue to digital. Then a mathematical software operation takes place that separates all the signals into separate frequency components. A software defined filter is then used to select the required signal. Demodulation of that signal is carried out in software. That signal is the converted back to analogue and fed to a speaker.
Signals are fed to an antenna by coax cable or twin feeder, antennas are designed to work on specific frequencies. Lower frequencies require longer antennas.
Shape your QSO’s (amateur radio conversations).
Don’t worry about it too much the people you are with will prompt you but a basic idea is here.
HF Radio
High frequency (HF) is the ITU designation for the band of radio waves with frequency between 3 and 30 megahertz (MHz). The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio.
Because radio waves in this band can be reflected back to Earth by the ionosphere that is a layer in the atmosphere by a method known as “skip” or “skywave” propagation these frequencies can be used for long distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications. The band is used by international shortwave broadcasting stations (3.95–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.
The normal means of long distance communication in this band is skywave propagation, in which radio waves directed at an angle into the sky refract back to Earth from layers of ionized atoms in the ionosphere. By this method HF radio waves can travel beyond the horizon, around the curve of the Earth, and can be received at intercontinental distances. However, suitability of this portion of the spectrum for such communication varies greatly with a complex combination of factors.
Antenna type and location, the power of the transmitting station and local interference.
Sunlight/darkness at site of transmission and reception/ greyline
Season
Sunspot cycle
Solar activity
Polar aurora
When all these factors and more are at their optimum, worldwide communication is possible on HF. At many other times it is possible to make contact across and between continents or oceans. Much of the skill in HF operation is predicting patterns of propagation
When a transcontinental or worldwide path is open on a particular frequency, digital, SSB and Morse code communication is possible using surprisingly low transmission powers, often of the order of milliwatts, provided suitable antennas are in use at both ends and that there is little or no artificial or natural interference.
VHF
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter.
VHF radio waves propagate mainly by line-of-sight, so they are blocked by hills and mountains, although due to refraction they can travel somewhat beyond the visual horizon out to about 160 km (100 miles). Common uses for radio waves in the VHF band are Digital Audio Broadcasting (DAB) and FM radio broadcasting, television broadcasting, two-way land mobile radio systems, local and trunked amateur radio communication (emergency, business, private use and military), Air traffic control communications and air navigation systems (e.g. VOR and ILS) work at distances of 100 kilometres (62 miles) or more to aircraft at cruising altitude.
In amateur radio the VHF / UHF bands are used for local Communications, trunked systems often via the internet and satellite communications. It is possible to speak with the international space station on VHF. The space station also carries a repeater allowing amateurs to communicate with each other via the station.
DMR
DMR or Digital Mobile Radio
Tier 1: The simplest form of DMR is Tier 1, which is mainly used for simplex communications, with no repeaters. The human voice is digitally sampled and compressed with the AMBE+2 codec, and then transmitted in this digital form to another radio.
Tier 2: Things start to get a bit more complicated here. With Tier 2 DMR, repeaters are used in a TDMA arrangement, with two “timeslots. What this means is that two completely separate radio transmissions can be going through the repeater at the same time; each radio takes turns in transmitting in short 27.5 millisecond bursts. In addition to this, radios can be set to logical closed groups called ’talk groups’, which you can think of as ’virtual channels’. Repeaters can be linked via the internet to form networks that can be as small as just two repeaters, or thousands of repeaters across the world. Again, the AMBE+2 codec is used to turn speech into compressed data for transmission. All amateur radio DMR systems are Tier 2, as are many business / commercial radio DMR systems.
Tier 3: This is effectively a trunked radio system on top of Tier 2. A pool of frequencies are used to carry the TDMA transmissions. This is used by more complex or larger networks for big businesses and commercial radio users.
The advantages of DMR:
So why go to all this trouble, when plain old analogue VHF / UHF FM works perfectly well? DMR has the advantage that it four times more efficient when it comes to spectrum usage. For one 25 kHz analogue FM channel, you could fit four DMR transmissions. Not only that, but DMR offers some very flexible calling facilities – you can call one person, a group of people, or everyone in your fleet at once. While not every DMR network supports it, sending of data and short messages is also possible. DMR is also designed to be easy to network, with connections using IP, so creating wide coverage areas using a network of DMR repeaters is already built-in; cover your city or cover the entire country! Yet another advantage is because a DMR transmitter is only turned on about half the time due to it transmitting in bursts, battery life is longer.
It also has the advantage of country or World wide amateur radio on a budget. while not the same thrill as bouncing signals off of the Ionosphere. A complete DMR setup of a radio and hotspot can be purchased for under £100 with no external antennas needed. As a start into amateur radio the foundation exam and a DMR radio gets you on the air at a low price. Ideal for University or College accommodation.
TYT DMR radios can be purchased for around £60
Some DMR Jargon:
Colour codes: Every DMR transmission uses a “colour code” which is very similar to CTCSS or PL tones in the analogue radio world. On a repeater or simplex frequency, every radio must use the same colour code to be able to communicate together. The main use for colour codes is for where two repeater coverage areas on the same frequency may overlap, different colour codes are used to ensure each radio accesses the correct repeater.
Timeslot: For Tier 2 and 3 systems, a timeslot is a slice of time, about 30ms long, that a radio can transmit in, or receive in. There are two timeslots per frequency, and you need to have your radio configured for the right colour code for the repeater, the correct timeslot and correct talkgroup for you to be able to hear anything.
Zones: This is simply a collection of channels & talkgroups, all grouped together in one “zone” or bank. A radio user can switch zones to access a different lot of channels & talkgroups that they may wish to use. Typically a zones are divided into repeaters for different areas, so you might have one zone for the west side of a city, and another covering the east side of the city – but there’s nothing to say that you must set up a zone that way.
Code Plug: This is a Motorola term that has stuck over the years, and in the DMR context means a complete configuration file of channels, talkgroups, zones, contacts etc. for a radio. The code plug can be saved to computer disc, and is used to program a radio to give it the functionality a user requires.
CPS: Another Motorola term, meaning Customer Program Software. Simply put, this is the software you’d use to create a “code plug” and configure your radio.
Hotspot: A small box that connects to the internet and acts like your own personal low power DMR repeater, useful if you’re not in range of a DMR repeater to access. You can even take them with you and use your cell / mobile phone wireless data to connect the hotspot to the internet and be able to use DMR anywhere you get cellular signal. Most hotspots are multi-mode, handling not only DMR but DStar, Yaesu Fusion and P25, hotspots that you can easily build yourself using a raspberry pi start at about £40.
The Bomber aircraft in WW2 used Morse code for communication in general. This is because Morse code worked better with the type of radios in use in those days and is still today a strong form of communication in poor conditions. Morse code is as you know is made up of tones or flashes of light of two different lengths representing letters and numbers. A is Dot a short tone or flash of light, a Dash a longer one.
In those days they had separate transmitters and receivers the transmitter is on top the receiver underneath in the photo above. The transmitter is the T1154 the Receiver is the R1155.
The Dots and Dashes represent the letters and numbers as shown in the chart below. What is important to remember when first trying Morse code is that all the dots and dashes of a letter must come very quickly together. For example the letter A = \.- \ but it we key \ . gap – \ we get the letters E and T because of the gap being too big between the dot and the dash. As the pause represents the start of a new letter.
With the aid of the chart
See if you can work out this word \– \.- \-. \-. \.-\
How about this one \-.-. \…. \— \.– \….\ — \..- \-. \-..\
Or this one \.-.. \.- \-. \-.-.\ .- \… \- \.\ .-.\
One with some numbers \- … \ . – – – – \ – – . . . \
Try writing some messages of your own out on paper.
This button above will open a page where you can try to send your message using the space bar of your computer. If you are using a tablet or phone there are free apps you can download and use instead.
A dot is a very quick press a dash you need to hold the space bar down for 3 times as long as you did for your dot. It is a really difficult skill to master just to send your name without having to learn the sounds to be able to understand the incoming messages. In WW2 it was a six month training course to become a radio operator. It was very important for the radio operator to listen to his radio all the time they were flying incase of bad weather reports, the operation being cancelled or anything else.
Morse code is alive and well and still in use by many amateur radio operators as it is still a very efficient mode.