Stevenage And District Amateur Radio Society
Talk Notes
For Sale

EME - Earth Moon Earth

Latest from M0XJP

KP4AO works EME with the Arecibo radio telescope
The Arecibo Observatory Amateur Radio Club will put the 1000-foot radio telescope on the air for three days for 432MHz EME. The scheduled times of operation for the final day today, 18 April, are 1840 - 2125UTC. Using the callsign KP4AO and 400W the transmit frequency is 432.045MHz and receive frequency is 432.050 to 432.060MHz. KP4AO can be heard with a small hand-held Yagi pointed at the moon and a good receiver. A 15dBi antenna and 100 watts will be enough to work them on CW. Operators at KP4AO will do their best to work as many stations as possible. Each session will start with a brief announcement and CQ in SSB. SSB QSOs may continue for 30 minutes to an hour if the QSO rate remains high. The mode will be shifted to CW as soon as it is judged that higher QSO rates would result. They will listen for calls at frequencies 5-15kHz higher than the transmit frequency and even higher if QRM warrants. The operators ask that if you've already worked them in any mode, please do not call again to give others a chance. On 18 April, if they reach a condition where most calling stations have been worked and they judge that operating in the digital mode JT65B would produce a higher QSO rate, they will switch to JT65B.


Background and more information - Edited

Dear all,

I've attached a pdf document containing common moon windows between my location in Stevenage (IO91wv, close enough for everyone to use) and KP4AO for 16th through 18th April. I've assumed minimum elevation capability of 70degs for Arecibo, as advised by K1JT. Good luck to anyone that tries!

73 Mark G4PCS


Just to help with interpretation of the table in the document: the important columns are the ones headed "UTC" (or "Local") giving the time; "HmAz" giving the beam heading (i.e. azimuth) to the Moon at that time; and "HmEl" giving the Moon's elevation.

Also possibly of interest: the column headed "HM-HM" indicates the doppler shift (in Hz) of one's own echoes at that time (on 432MHz, won't be audible without an EME setup!); and "HM-DX" indicates the doppler shift at which KP4AO's signal should appear. The doppler shift is caused by the relative motion of the Moon: as it rises in the "east" it is moving towards us (shift is +) and as it sets in the "west" it is moving away from us (shift is -). The doppler shift is zero when the Moon is approximately due south, when the relative motion is also zero.

You can stop reading here if you like - stuff below won't affect your ability to find KP4AO one jot :)

"Spatial" indicates the amount of polarity rotation caused simply by geometry. The simplest way to explain this is to imagine you are standing on the Moon looking back at Earth - if you were looking at a "horizontally polarised" antenna located on the equator on the western (or eastern) edge of the Earth's disc it would appear to be rotated by 90 degs compared to a "horizontally polarised" antenna at the north or south pole. This isn't a fixed value and changes considerably between different stations as the Moon passes overhead. Having said all that, it can generally be ignored because there's another effect that can rotate the polarity of a signal by an unknown amount - "Faraday rotation" - as it passes through the ionosphere.

Since the distance between the Earth and Moon differs considerably during the lunar cycle (of about 27 days), "dB" indicates additional path-loss compared to when the Moon is at perigee, i.e. it's closest point to Earth.

The sky contains lots of noise sources (galaxies including our own, black holes, etc) but the amount of noise varies depending on which part of the sky we're looking at. "Tk" indicates how noisy the sky is around the Moon's position (higher number is noisier). EME'ers look for "quiet sky" since this improves signal-to-noise, particularly important for marginal contacts.

73, Mark G4PCS


This is excellent. Thanks hugely. I'm assuming UTC = GMT. The doppler shifts should not be a problem. Assuming a 25kHz RX passband. Tell me if I'm wrong. The Faraday rotation is a new one on me. Interesting, but we can do nothing about it.  Similarly with noisy sky. I envisage a tripod-mounted Yagi with some sort of optical sight fitted, and a sober "assistant" to keep it aimed at the Moon during the windows of observation. Is this too simplistic?  It will probably be still daylight then. There are three windows: April 16th: 1645 - 1930 GMT  (Friday evening)
April 17th: 1740 - 2020 GMT  (Saturday evening)
April 18th: 1840 - 2125 GMT  (Sunday evening)

Thanks for an excellent explanation. Cheers, Tom G4BYE


Background and more information - Edited

Hi Alex,

You are indeed correct that the opportunity to work the Arecibo antenna is
worthy of a little effort. I remember working KP4BPZ from there on 70cm
EME around 1974/75 and a little later the rather smaller dish at SRI
(Stanford Research Institute, CA) all via the 4.5m homemade dish
belonging to a friend from the Watford area.
You should be aware that the club owns a an Icom IC-910X VHF/UHF
transceiver that covers 2m, 70cm and 23cm and runs 100W, 75W and 10W
respectively on each of those bands. It is currently locked away in the
equipment cupboard at the club and has not been used since we lost the use
of the shack.
I do have some spare antennas for 70cm although the feedpoint of at least one
is a little damaged, the other 2 maybe ok though.
I am copying this mail to Mark, G4PCS who has the moon data on his laptop
and should be able to advise on the moon window for the weekend.
I will not be at hme on Sunday 18th April because of a prior UK Microwave
Group Round Table meeting at RAL in Didcot and will not be at the club next
Tuesday because of a UK Microwave Group teleconference committee meeting.
Maybe you can ask one of the committee members at the club to dig out the
IC-910 in case the opportunity arises to make use of it with its 75W output power.

One day I hope to take a holiday in Puerto Rico and to visit the visitor center at
Arecibo although this is some way from the antenna as the site is US Government

Bryan, G8DKK

Arecibo on 432 MHz Moon Bounce The Arecibo Observatory Amateur Radio Club will be putting the 1000-foot radio telescope on the air for 432 MHz EME from April 16-18. It can be heard with a small hand-held yagi pointed at the moon The scheduled times of operation are: April 16: 1645 - 1930 UTC April 17: 1740 - 2020 UTC April 18: 1840 - 2125 UTC Callsign: KP4AO Tx Frequency: 432.045/*