# EME

(Earth-Moon-Earth)

or "moonbounce"

I became interested in EME because of the challenge it represents.

It is truly "weak signal" communications, placing a premium on the efficiency of the transmitter, the performance of the receiver, the gain of the antenna, and of course the skill and patience of the operator.  The "typical" round-trip path loss when the moon is at perigee (closest to the earth) is approximately 251.5 dB at 144 MHz.  If you consider a system where maximum legal power is present at the antenna, the system starts with 31.76 dB transmit power.  If the antenna array has 19 dB gain, then the signal leaving the antenna will be 51 dB.  The signal arriving back from the moon at the receiving antenna will be on the order of -200 dB.  If the receiving antenna also has 19 dB gain, the signal arriving at the preamplifier on the mast will be -181 dB.  If the antenna has a noise temperature of 200 K, the preamplifier has a noise figure of 0.5 dB, the subsequent 144 to 28 MHz transverter a noise figure of 1 dB, and each has a gain of 20 dB then the receive system will have a noise floor of -187 dB  if a bandwidth of 250 Hz is used. (As long as the 28 MHz IF is reasonably state of the art, its noise figure is irrelevant as it is divided by the product of the gains of the preamplifier and the transverter when figuring its equivalent noise temperature).  Thus the receive system will detect the signal as (-181+187) or 6 dB above the noise.  Throw in a couple of dB for cable loss, and you may be 2-4 dB above the noise.  Compare this with a typical  1 watt HT at 10 kM with a 0 dB gain antenna, where the received signal would nevertheless be 60 dB OVER the noise (or roughly a million times stronger)!  Or an astronaut using a 1 watt HT at 1000 kM from you, who would still be 20 dB above the noise!  Thus EME IS truly weak signal work!

My 144 MHz station consists of a 2 x 2 array of 4 M2 2MXP32's, separate LNA Technology  CAV-EME receive preamps for each receive polarity mounted on the mast at the power divider, LMR-600 Ultra-Flex cable to the ground [separate runs for Receive Horizontal Polarity, Receive Vertical Polarity, and Transmit], and then 3 separate runs of Andrew Hardline to the shack.   The receiver is the WSE series hardware from SM5BSZ used with his Linrad software receiver. For transmit the transverter is an SSB Electronics LT2S-Mk II fed by a Yaesu FT-1000MP Mk V.  The Linrad Receiver pulls out weak EME signals that I couldn't hear any other way, and shows me nearly 100 kHz of the EME band all at once!  The antenna control is taken care of by a Green Heron Engineering RT-21azel rotator controller driving an M2 Orion 2800 rotor for Azimuth and an M2 MT-3000 rotor for Elevation.  For power I have a 2 x GU-74B amplifier crafted by Marko Tsekov, LZ2US.

My 10 GHz station is portable at the moment, I drive it out and set it up when I want to operate.  See here for details.

Ever wonder how to decide where to locate your dish? Click here to find out.

Not sure how to create a log for the ARRL EME Contest? Click here to find out.

Interested in learning more?  Start with the links below.

Real-time JT-65 EME Activity Logger; see who's on!!

SM5BSZ:  Polarity Switching, DSP, Software Receiver, Power Amps,...

EA6VQ's Home Page

DUBUS Information Site

AF9Y's Home Page:  EME, FFTDSP, and more!! This is a dead link...let me know if you know a good link for this page

Hear me (W3SZ) in EME qso with VE7BQH, as heard in Sweden by SM7SJR

Copyright © 1997-2007 COPYRIGHT Roger Rehr W3SZ. All Rights Reserved