|On April 16, 17, and 18, 2010 the 1000 foot dish at Arecibo, PR will
be activated for amateur EME contacts on 432 MHz amateur band. Since the 1000 foot dish has such a large amount of
gain (60 dbi), it will be easy for modestly equipped stations to work them
via moonbounce. These pages are intended to help newcomers to
moonbounce prepare for their attempt to work Arecibo.
NOTE: Added pictures of my setup for trying to work
Arecibo: My Station
|The first thing you need to know is whether it will be possible for
you to work Arecibo. If the Moon is not visible to you during the
times that the Arecibo dish can 'see' the moon, then there would be no
chance for a contact. I have prepared ground maps showing the
portions of the earth that can see the moon when Arecibo can.
There is a separate page for each day, but there is really very little
change, day to day. If you live near the edge of their coverage
then you may wish to study the maps closely. For stations in North
and South America, most of Europe, most of Africa, and in Hawaii, it
should be possible to make a contact. Unfortunately there is no
opportunity for stations in the most of the rest of the world.
Study the maps to be sure. Click this link to view the maps:
Arecibo Moon Coverage Maps
The Arecibo dish can only see the moon when it is high overhead, and for a limited time of about 2.5 to 3 hours each day. This is because the aiming of the 1000 foot dish is limited to a maximum of 20 degrees from vertical (straight up, or 90 degrees). Thus Arecibo can only see the moon when it is above 70 degrees elevation, as shown in the maps.
|The operation at Arecibo is being run by the Arecibo radio club, using the call KP4AO. The grid square is FK68OI. They will be transmitting on 432.045 MHz, and receiving in the range from 432.050 to 432.060 MHz. In case of heavy congestion they will tune even higher for callers. On all three days KP4AO will start working SSB for the first 30 minutes or so of their moon window. Then they will switch to CW to work the weaker stations. On April 18, if activity on SSB and CW seems light, they will switch to the JT65B digital mode. Using JT65 it will be possible to work them with much less power or antenna. However JT65 contacts take a lot of time, so they will only be able to work a limited number of stations in that mode. It would be best to try to work them on CW and resort to JT65 only if necessary. Since Joe, K1JT, will be one of the operators at KP4AO it is certain that they will be very efficient at their JT65B operations. Official K1JT Arecibo Announcement (includes QSL info).|
|Next you need to know what kind of equipment will be needed to work Arecibo.
You will need a transceiver or transverter capable of receiving and transmitting
SSB and CW in the 432 MHz amateur band. For CW contacts, 100 watts should
be enough power if you have an antenna with at least 13 db gain (db over a
For 432, an antenna with that gain is likely to be about 6 feet long and have 10 or 11 elements. Thanks to Kent, WA5VJB, construction details of such an antenna are presented here: WA5VJB 11 element 432 Yagi.
A number of people have asked about polarization. Since Arecibo's dish uses circular polarization it does not matter whether your Yagi is horizontal, vertical, or somewhere between. If you have circular polarization available, you can get an increase of 3 db in both transmitted and received signal, but I do not know what sense KP4AO will be using so you would have to determine it by trial. It is much simpler to just stay with linear polarization.
It is certainly possible to make a contact with less power or antenna, but there is likely to be quite a bit of competition during the limited operating time, so try to be as capable as you can. For SSB contacts more power will be required. For the same antenna, 300-400 watts would be a minimum to expect a SSB contact, and 800w would be better. Of course a larger antenna will reduce the power requirements as well as making it easier for you to hear the signals from Arecibo.
|The moon will be high in the sky, so you should expect to build up some sort
of temporary support structure that will allow you to aim your antenna up and
manually position it to point at the Moon. Ideally the support structure
should be as low to the ground as possible and still allow the back of the
antenna to clear the earth when pointed up.
If you can see the moon, all it will take is a visual aiming. Lay on your back under the antenna and sight along the boom to verify that the boom is pointed straight at the moon. For short antennas this is not very critical and generally within 10-20 degrees will work.
If you cannot see the moon (due to cloud cover) then you need a program to tell you where the moon is at your location at the current time. Then you will need a way to measure and set the elevation and the azimuth of the antenna. Elevation can be measured easily with a level and a protractor, or a simple gravity operated inclinometer such as sold for a few dollars in most any hardware store.
Azimuth can be measured with a compass, but make sure you take into account the offset in your area between true north and magnetic north. An easy way to determine how much offset you need for your compass headings is to see how much difference there is between your compass heading and the location of the Sun. Any Moon program will also show Sun locations so this is easy.
|To work KP4AO you must first
be able to hear them, so listen carefully until you have determined
their frequency and current mode of operation. Then you can start
calling them when they stand by after a contact or a CQ. You must
operate 'split', receiving on 432.045 and transmitting somewhere above
432.050. They will not be listening on their transmit frequency.
Since signals are expected to be strong, you can use standard RST signal reports. If you prefer you can use standard moonbounce reports of O and RO. Once you have worked them, please do not try to do so again. With such a limited time operation it is important to give others a chance. If you hear them call for low power stations, do not call them unless you are running 100 watts or less.
Very 73, Russ K2TXB - FN20MB (MB for Moon Bounce)
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