How high the Moon [1965] (the story of first UHF EME in Europe)
Once upon a time, there were 5 radio amateurs:
a dentist, a communication engineer, a camerama an RF engineer and a noodle manufacturer
For them, the normal distances covered by amateur radio were too short and the wavelengths too long
Shorter wavelengths were within reach, however, concerning longer distances
the had to take the Moon as a reflector and try to get an echo
For this reason, a discarded parabolic dish was organized and brought through customs with some difficulties across the border
and then installed in front of HB9RF's house
As is well known, every "Ham" is a universal genius, therefore the project got on its feet according the schedule
The reason that HB9RG became project leader is due to the fact that he is the strongest
that he carries a whip and that he is used to issue high dentist's bills
His first name is ,Hansrudi', but in the course of time HB9RG got some nick-names such as ,Torturer' and ,Slave driver'
Also Eddy, DL9GU makes the impossible possible, but Heninrich is calm and quiet
He is the member with the largest high-frequency experience and the builder of the most complex equipment
And this, that is me [HB9RG]. My good position - not the financial
but the geographical one, and the fact that I'm good humored and that antennas grow well on my farm
made me victim number 3. Perhaps, also the fact that I am interested in Astronomy helped somewhat
After 2 years of construction, we were in a position to hear our own CW echo off the Moon in 1962
The dalay was approximately 2,5seconds, corresponding to the Earth-Moon-Earth distance of approx 770'000km
devided by the speed of light.
This gave proof to us, that our signals were indeed reflected by the Moon
The efficiency of our system was still very much limited.
For instance, the connection of the coaxial cable for either transmit or receive was still done by hand
which could just be accomplished in about 2,5 seconds
Encouraged by our success, we continued making refinements to our system for another 2 years
In 1964, we succeeded in making our first transatlantic QSO on 432 MHz via the Moon with a station in Puerto Rico
Professor Pettingill (W1OUN), put his 305m antenna to use and the test was a success right from the beginning
His antenna is located at Arecibo and the reflector of spherical shape is embedded in a natural volcanic crater
The feed is movable and has a radiator angle of +-20 degrees
The purpose of this system is to do research on the Ionosphere and the space between planets
As Prof Pettingill is himself a radio amateur, he used the time slot between two research projects
to run an Earth-Moon-Earth QSO with our european station
Let's now leave this $80 Mio project and return to the home of HB9RF
This parabolic antenna is mounted in parallel to the Earth axis
Originally, it had a diameter of 5,2m and the radiator was a 2el yagi
A discarded elevator motor is used to control the azimuth and the feed is now a tin-can horn radiator
The declination is set by a manually operated wheel. The range is +-/30 degrees indicated on the calibrated dial
The azimuth can be set by a push-button switch to any position from South to West
During our tests, we used the Sun as an ideal noise source
If our dish is properly set to the Sun, the noise increases by some dB
as can be seen on this instrument and verified by a calibrated attenuator
All measured data are recorded and kept for futher improvement of our system
The eletronic equipment is housed in an old VW van placed immediately adjacent to the antenna
At these frequencies, the nitroge-filled coaxial cables have to be as short as possible
The basic freuquency of the transmitter is derived from an 8 MHz xtal-oscillator
which is buried 2m deep in the most shadowy place of the garden
After triipling, the basic frequency is compared with the standart frequency signal of Droitwich - oscilloscope
and it is then used for futher multiplication.
After feeding the 1296 MHz signal to the driver stage, consisting of 2 tubes 2C39 and yilding a power of 50W
it is then routed to the final amplifier with a single tube 7650 production an output of roughly 500W at 1296 MHz
The decoupling of the respective power is done by a variable capacitor which can precisly be adjusted
After passing through a directional coupler, the output signal arrives at the transmit-receive switch
On the receiving side, the antenna signal passes through a parametric amplifier. After conversion to shortwaves
a Collins receiver demodulates the receive signal.
The required bandwidth for CW signals is accomplished by a 100 Hz filter
Eddy, DL9GU is about to replace a punctured mica isolator disc since tomorrow morning we wish to EME again
The entire system is chedked point by point:
the cavities of the driver stage,
the large and small blowers
Everything seems to be in order.
During this preparation, I'm about to calculate the position of the Moon
vs. time, as we also operate when the Moon is not visible due to clouded sky
With the help of the Nautical Almanach, the position of our antenna is calculated in 5 minutes intervals
The result is a list of very important numbers as the moon is the most unstable sky object there is.
For the upcoming experiment Eddy has built something special again, but he should explain it himself
"It's a hybrid which can feed an antenna with right and left polarization without having to switch".
So the hybrid is professionally mounted.
By the end of the day the boss explains:
At 5 AM we're gonna make an EME test on 1296 MHz with W2NFA (W2IMU) from Crawford VHF society
Howgh, I have spoken.
Punctually on the second we're starting our CQ moonbounce.
We call 10min long and then we switch to RX
After the switching it takes at least 5 seconds untilthe signal can be heard.
That results from the running time of both signals over 1,54 million kilometers i.e double path Earth-Moon-Earch
The frequencies can be adjusted up to a few Hz.
Nevertheless, the signal of the counterpart station must be sought after every over.
The moon moves relatively against the earth and causes a doppler effect plus/minus 2.5 kHz depending on the angle.
Before we could receive the signals so loud and clear we had to permanently do improvements with a lot of patience and energy. At the same time.
"..sp de kp4biz k (bpz)..."
Eddy has done his professorship on parametric amplifiers.
HansRudi tried to press out the last watts from our ceramic tube.
500 watts UHF was the goal which our first 7650 couldn't handle.
The improved fans for the driver and PA,
a high precision coupling and a perfect RX/TX switch were just a couple of things which were inevitably necessary to achieve that.
The optimal antenna rectification took 3 months as we could use only clear nights to aim to fixed stars on the sky.
The moon reflected our signals as expected.
First with CW than as a coronation also SSB we have worked with our partners overseas 8 years.
Naturally we are proud that we managed as a first european team to find a cost free satellite dish.
In the years to come the commercial services surely will evaluate our success as all other pioneer achievements hams provided with their hobby.
The End