RADIO EXPERIMENTS
The Rutherford Appleton Laboratory, one of our sponsors, gave this experiment to us. They wanted us to do this as a trial for a national experiment based on our findings.
The experiment was to investigate the effect the eclipse has on the ionosphere. Is it similar to the way it is effected at dawn and dusk?
Experiment Description
The way in which we measured this change was to find an AM radio station that we could hear at night time but not during the day, then listen for changes in this station during dusk, dawn and the eclipse. The station should fade in (become audible) during the first set of partial phases and fade out between third and fourth contact. The ideal type of radio station is one that is audible at night, but not during the day and comes from an antenna that’s around the globe or over the horizon from your position. So, before we went out to Curaçao we tried our equipment by tuning into a Spanish radio station that we had selected the night before and recorded it at sunrise; it did fade out and we worked out an actual time for this change.
We worked out the time of the change in the ionosphere by starting to record the selected radio station at an exact time using a timer switch. Afterwards we had to listen to the tape and time how long it took to get to the place where the radio station was no longer audible. The two times were added and there was our result. This is what would have happened in Curaçao if we hadn’t been faced with so many problems!
Problem after problem!!
After we had tried this experiment in England, and it had worked, we were quietly confident that we could obtain some impressive results and show them to the Rutherford team with great pride, but due to several problems we had out in Curaçao this became very unlikely.
The first problem we came across was how to identify where a radio station is broadcasting from. Here, in England it was easy, a Spanish speaking station came from Spain, a Portuguese speaking station came from Portugal. In Curaçao there were over 40 different nationalities on the one island so there were hundreds of radio stations that sounded Spanish (Venezuela) or American (America) but were actually broadcasting from Curaçao. This meant that we couldn’t tell whether the radio station might be suitable by the language or style so we had to think of something else. We decided to list all the radio stations we could hear at night then list all those audible in the day and try to find one that was not there during the day. This is where we hit problem number two.
The radios we had were cheap and readily available analogue tuning radios. When we started to list the radio stations we needed some way of identifying them and knowing that we couldn’t use the language of the station we decided to use the frequency. This proved more difficult than it sounds, because the radios we had were analogue, the frequency slides were about ten centimetres long to accommodate the 500 - 1600 kHz AM wave band or 100 different radio stations. As you can imagine finding the frequency from this dial was extremely difficult. To help identify the radio station we recorded the strength of the signal. We made many lists but couldn’t find a radio station that satisfied our conditions.
Yet another problem we found, was that the Curaçao mains voltage was not stable enough to use our radios with, so we had to change to batteries which didn’t help as now we could not use the automatic plug-in timers.
One day before the eclipse, slightly worried now that the experiment might be a complete failure, we borrowed a digital tuning radio, which had the frequency on a liquid crystal display. This enabled us to know the exact frequency of the station, which we thought, would help, but due to this new radio having a higher sensitivity than our other radios it picked up many even weaker stations. Now between 500 kHz and 1600 kHz we only had about ten broadcasting gaps that our station at night could appear in. That night (the night before the eclipse) we thought we had found a suitable station. It definitely was not there during the day and we could hear it at 1:00 am perfectly clearly. We tuned our analogue radios into this station and stuck the dials down with brown parcel tape to prevent the frequency changing.
Eclipse day we woke up with renewed enthusiasm towards this experiment and picked up our radios to check that the new station we had found had faded out at dawn, but it was louder than before. We then almost gave up! But still recorded this station during the eclipse to see if any thing changed: it didn’t.
Luckily it was not quite a complete failure as it told us and the RAL team that the experiment would need to be refined. (Which it has been)
In the U.K.
In the UK in 1999 this experiment will work a lot better as there will be no problem with the electricity supply, the foreign stations are easy to identify and there are much tighter controls in Europe on when and at what frequency people can broadcasts at. This means that accurate lists of all the radio stations that are broadcasting at what time can be found making finding a suitable station much easier. Also the most accurate place to do this experiment is actually under the partial phases of the eclipse.