EarthMoonEarth Communications

1
Earth-Moon-Earth Communications
By W3SZ, Roger Rehr
2
First EME

• Project Diana U.S. Army Signal Corps
• January 10, 1946
• 3000 watts, 111.5 MHz
• John DeWitt, N4CBC

3
Amateur Radio EME Firsts

• January 27, 1953 W4AO and W3GKP heard their EME
  echoes on 144 MHz did not complete QSO
• July 21, 1960 W6HB Eimac Radio Club and W1BU
  worked each other on 1296 MHz EME
• First Complete Amateur Radio EME QSO
• California to Massachusetts
• April 11, 1964 First 144 MHz EME QSO, between
  W6DNG and OH1NL
• May 20, 1964 First 432 MHz EME QSO, between W1BU
  and KP4BPZ Aricebo

4
Amateur Radio EME Firsts

• 1970 First 222 MHz QSO, WB6NMT / W7CNK
• 1970 First 2.2 GHz QSO, W4HHK / W3GKP
• 1972 First 50 MHz QSO
• 1987 First 3.4 GHz, 5.7 GHz QSO
• 1988 First 902 MHz, 10 GHz QSO
• 2001 First 24 GHz QSO, W5LUA / VE4MA
• 2005 First 28 MHz QSO
• 2005 First 47 GHz QSO, W5LUA / AD6FP / RW3BP

5
Amateur Radio EME

• An extreme weak signal challenge
• Typical round-trip path loss at perigee is 251 dB
  at 144 MHz
• If 1500 Watts out 32 dBw transmit power 62 dBm
• If antenna array has 19 dB gain, signal leaving
  antenna will be 51 dBw 32 19 dB
• Signal arriving back from moon will be -200 dBw
• 51 251 dB
• If receive antenna has 19 dB gain, signal from
  antenna will be -181 dBw -200 19 dB

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EME signal levels

• -181 dBw signal out of antenna to receive preamp
• 8 x 10(-19) watts .0000000000000000008 watts
• If antenna has noise temperature of 200K, preamp
  has noise figure of 0.5 dB, 144-28 MHz
  transverter has noise figure of 1 dB, and each
  has a gain of 20 dB, then receive system noise
  floor will be -188 dB with 50 Hz bandwidth filter
• Thus received signal will be 7 dB above the noise
  188 -181 dB

7
EME signal levels

• So EME signal at perigee closest approach of
  moon to earth is 7 dB above the noise
• Add 2-4 dB for cable loss, and signal is only 3-5
  dB above the noise with 19 dB gain antenna and
  full legal limit transmitter power 7-25 dB,
  7-43 dB
• Compare Signal from a 1 watt HT at 10 km with 0
  dBi antenna would give signal strength at the
  receive antenna of -96 dBw, or -77 dBw at preamp
• 104 dB or 25,000,000,000 times stronger than EME
  signal
• -96 (-200) 104 dB

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EME signal levels

• What does it take to get 19 dB antenna gain at
  144 MHz?
• M2 2MXP20
• 260 inch boom length 21.66 feet
• 13.2 dB gain
• Add 6 dB for array of 4 arranged as 2 x 2 array
  with spacing of 156 inches 13 foot square
• 19.2 dB

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EME signal levels with smaller antenna and / or
less power

• With just one M2 2MXP20 instead of four, and 1500
  watts, working similar station
• 13 dB antenna gain instead of 19 dB gain - 6 dB
  for Tx and Rx
• 7-9 dB below noise instead of 3-5 dB above noise
  in 50 Hz bandwidth
• 3 12 -9 dB, 5 12 -7 dB
• With 200 watts out instead of 1500 watts out,
  working similar station
• 23 dBw instead of 32 dBw transmitter power -9
  dB
• 4-6 dB below the noise with 2 x 2 array 2MXP20,
  in 50 Hz bandwidth
• 3 9 -6 dB, 5 9 -4 dB
• 16-18 dB below the noise with single 2MXP20, in
  50 Hz bandwidth
• -6 12 -18 dB, -4 12 -16 dB

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EME signal levelsEffect of narrowing receive
bandwidth

• If we reduce receive bandwidth by a factor of 10
  i.e. from 50 to 5 Hz, then we increase S/N by a
  factor of 10 10 dB
• Signal level of 7-9 dB below the noise with
  single yagi and 1500 watts becomes 1-3 dB above
  the noise -7 10 3 dB, -9 10 1 dB
• Signal level of 16-18 dB below the noise with
  single yagi and 200 watts becomes 6-8 dB below
  the noise

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EME signal levelsEffect of extreme bandwidth
reduction

• WSJT mode JT65B has 5.38 Hz bandwidth, so
• Signal level of plus 1-3 dB with single yagi and
  1500 watts working similarly equipped station is
  achieved
• Signal level of minus 6-8 dB with single yagi and
  200 watts working similarly equipped station
  needs additional boost!

13
EME signal levels with WSJT JT65BAdditional gain
by signal averaging

• With a single yagi and 200 watts, working
  similarly equipped station, received signal will
  be between 6 and 8 dB below the noise
• Signal averaging will classically increase
  signal-to-noise ratio by N0.5
• So 4 averages will increase SNR by a factor of 2,
  or 3 dB
• But with JT65 decoder, can get effective 4 dB
  increase in SNR with 4 averages
• Thus 6 to 8 dB below the noise becomes 2-4 dB
  below the noise with 4 averages for WSJT

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EME signal levels with WSJT JT65B

• So, for a single yagi with 200 watts working
  similar station with 5.4 Hz receive bandwidth and
  4 signal averages signal is 2-4 dB below the
  noise
• Are there additional losses or gains in the
  path?
• Fortunately, Yes!

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Natural Influences on EME Signal Strength

• Path Length
• Calculations we did were for perigee minimum
  distance, as little as 356,400km
• At apogee maximum distance, as much as
  406,700km path loss is about 2 dB worse 253.5
  dB
• Successive apogees or perigees are
  approximately 28 days apart

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Earth Moon Distance
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Natural Influences on EME Signal Strength

• Spatial Polarity
• At times, due to geometry, station signal
  polarizations may be 90 degrees out of alignment
  horizontal vs vertical
• This geometric effect is dependent on the
  relative positions of the two communicating
  stations and the moon

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Spatial Polarity
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Effect of Polarization Misalignment

• 
  by
  K1JT

21
Spatial Polarity
22
Natural Influences on EME Signal Strength

• Faraday Rotation
• Free electrons in the ionosphere cause rotation
  of a linearly polarized signal on trips up and
  down through the ionosphere. This rotation is
  called Faraday Rotation
• Magnitude is proportional to the local free
  electron density, and thus it is constantly
  varying and not absolutely predictable
• Greater during daylight hours than at night
• Greatest variability is near sunrise or sunset,
  due to rapidly changing ionization levels
• Also proportional to parallel component of
  Earths magnetic field
• Greater for stations farther from the equator
• Rotation is in same direction and thus cumulative
  on trips up and then back down through the
  ionosphere up and down trips do NOT cancel each
  other

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Faraday Effect
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Natural Influences on EME Signal Strength

• Faraday Rotation
• Because electron density is not constant, Faraday
  rotation causes constantly changing received
  signal polarization
• The amount of rotation and its rate of change
  is proportional to 1/frequency2
• Amount of rotation and changes in rotation are 9
  times greater on 144 MHz than on 432 MHz
• Period 30 minutes on 144 MHz, vs several hours
  on 432 MHz
• Magnitude typically up to many complete
  rotations on 144 MHz, vs only one complete turn
  on 432 MHz
• Only has minor effect above 432 MHz

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Faraday Rotation

• When spatial-polarity-induced misalignment is 90
  degrees, stations cannot work unless Faraday
  rotation adds additional rotation to 'cancel out'
  the unfavorable geometry
• Because of spatial-polarity-induced polarization
  misalignment, without Faraday rotation many EME
  contacts would not occur
• Faraday rotation is not evil, but necessary.
  The problem occurs when Faraday rotation and
  geometry combine to produce 90 degree misalignment

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Faraday plus Spatial Geometry
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Natural Influences on EME Signal Strength

• Libration
• The moon appears to 'rock' slightly in its orbit.
  In addition, its surface is jagged. These
  conditions lead to varying constructive and
  destructive interference, which can boost or
  reduce incoming signal by up to 10 dB, leading to
  fades up of up 20 dB
• A single yagi 200 watt signal could go from 2-4
  dB below noise to 6-8 dB above the noise or to
  12-14 dB below the noise
• Rate of change is proportional to frequency
• Frequency range is 0.1-1 Hz on 144 MHz period
  1-10 seconds
• 1-10 Hz on 1296 MHz
• 10-100 Hz on 10 GHz
• CW characters may sound chopped up on 1296 MHz
• CW signals sound like Aurora on 10 GHz

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Libration
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Libration
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Libration

• Maximum libration flutter frequency occurs near
  moon zenith
• Minimum libration flutter frequency occurs near
  moonrise or moonset
• Lunar libration magnitude varies with a
  periodicity of approximately 27 days, and can be
  predicted.

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Libration at 1296 MHz near zenith
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Libration at 1296 MHz near moonrise
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Libration magnitude vs time
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Libration Magnitude vs time
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Natural Influences on EME Signal Strength

• Sky noise
• Moon travels across the sky with a period of
  approximately 28 days, following the ecliptic
  the plane of the Earths orbit around the sun
• Stars and SUN increase background noise level
  when moon is 'near' them and will reduce SNR
• Magnitude of effect depends on beam width of
  antenna
• Optimal EME conditions occur all other things
  being equal when the Moon is far from the Sun or
  the Milky Way

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T-sky Map for 144 MHz K1JT
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T-sky Effect for 144 MHz
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Declination

• Distance of the moon from the celestial equator,
  in degrees
• Greater positive declination leads to higher
  lunar zenith in Northern Hemisphere moon higher
  in sky
• Varies from maximum to minimum to maximum again
  with a period of one month
• e.g. from 25 degrees to -25 degrees to 25
  degrees
• There is a wobble with period of 6 months in
  the maxima due to effect of Suns gravity on
  lunar motion
• Longer cycle of 18.6 years
• Maximal excursion of /- 18.5 degrees at minimum
  of long cycle
• Maximal excursion of /- 28.5 degrees at maximum
  of long cycle

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Declination Definition
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Declination vs moon path in sky
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Declination

• For Northern Hemisphere, greater positive
  declination is better
• Higher declination means
• More moon time
• Less terrestrial noise
• Lesser ionospheric effects
• One disadvantage of high declination is less time
  to work ZL, VK stations as they have less moon
  time

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Declination maxima vs time
43
Natural Influences on EME Signal Strength

• Scintillation
• The ionosphere causes 'twinkling' of radio
  signals due to constructive/destructive
  interference and can give up to 10 dB additional
  enhancement or loss
• Scales as (1/frequency)2
• Most prominent on 50 MHz, negligible on higher
  bands
• 10 times greater during daylight hours than at
  night
• Greater at low elevations than when moon is near
  zenith

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Natural Influences on EME Signal StrengthPutting
it All Together
45
Tracking the Moon
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Ground Gain

• When pointed horizontally, yagis will experience
  constructive interference between direct and
  ground-reflected waves for certain vertical side
  lobes, and the yagi may gain up to an additional
  6 dB gain for the elevation angles of those lobes
• This can be used to great advantage when the moon
  is near the horizon below 20 degrees!
• This effect is lost if you put your antenna high
  on a tower free space

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Ground Gain Example by ON7EH

• 2M12 by M2, 12.85 dBd free-space gain, on 10m
  tower

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Practical Effects of Signal Level Calculations

• Small stations 200 watt, single yagi will have
  great difficulty working anyone except 'big guns'
  using CW
• 1500 Watt, 4 yagi stations can work lots of
  similar stations and larger stations on CW, as
  well as some smaller stations
• With additional gain provided by narrow bandwidth
  and signal averaging of WSJT, a 200 watt single
  yagi station CAN do EME

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Practical Effects of Signal Level
CalculationsTypical CW Station Requirements
K1JT
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Doppler Shift

• Moonrise on 144 MHz up to 440 Hz
• Moonset on 144 MHz up to -440 Hz
• Zero shift when moon due North or South
• Proportional to frequency 9 times as great on
  1296 MHz as on 144 MHz
• up to approximately 4 kHz on 1296
• up to 30 kHz on 10 GHz
• Calculated by most EME Software

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Tracking the Moon

• Need to track / rotate both azimuth and elevation
• Unless you are going to work only below 20
  degrees elevation
• Then just need azimuth rotation
• Computerized tracking / rotation control
• Nova by Northern Lights Software Associates
• MoonSked by GM4JJJ
• EME System by F1EHN
• CCTV on antenna optional for visual tracking

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Tracking the Moon - Nova
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Tracking the Moon - MoonSked
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Tracking the Moon - MoonSked
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Tracking the Moon - MoonSked
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Tracking the Moon F1EHN
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WSJT Additional Gain the Digital Way

• Written by Joe Taylor, K1JT
• Shared Nobel Prize in Physics in 1993
• "for the discovery of a new type of pulsar, a
  discovery that has opened up new possibilities
  for the study of gravitation"
• WSJT makes the impossible possible
• Can work stations too weak to hear
• Can make QSOs with stations 10 dB too weak for CW
  
• JT65B on 144 MHz
• JT65B as it sounds at the mic input to the
  transmitter
• A Loud for WSJT F6FHP heard at IW5DHN
• A more typical signal DL7UAE at K1JT

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WSJT

• JT65B for 144 MHz 5.4 Hz bandwidth
• JT65A has 2.7 Hz bandwidth
• JT65C has 10.8 HZ bandwidth
• 64 tone frequency shift keying FSK
• 65th tone for synchronization
• Newer protocols are under development by K1JT

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Typical EME 144 MHz CW Contact

• 1 or 2 minute sequences, at 12-15 wpm
• Eastern station relative to International Date
  Line always transmits first even minutes
• CQ CQ CQ de W3SZ W3SZ W3SZ
• W3SZ de W5UN W5UN W5UN
• W5UN de W3SZ OOO OOO OOO
• W3SZ de W5UN RO RO RO
• W5UN de W3SZ RRR RRR RRR
• W3SZ de W5UN TNX 73 73 73

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Typical EME 144 MHz JT65 Contact

• 1 minute sequences
• CQ W3SZ FN20
• W3SZ W5UN EM23
• W5UN W3SZ FN20 OOO
• RO
• RRR
• 73

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Typical EME 144 MHz JT65 long form Contact

• 1 minute sequences
• CQ W3SZ FN20
• W3SZ W5UN EM23
• W5UN W3SZ FN20 -17
• W3SZ W5UN EM23 R -21
• W5UN W3SZ FN20 RRR
• TNX ROG 73 GL

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Listening to your own echoes

• Small stations wont be able to do this!!
• 2.56 second round trip
• IZ1BPN 1296 MHz self-echoes CW
• IZ1BPN 1296 MHz self-echoes SSB

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W3SZ and VE7BQH-CW EME QSO

• W3SZ 1500 watts and 2 x 2 2MXP20 array
• VE7BQH Canadian legal limit plus 384 element
  collinear array
• 144 MHz CW

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W3SZ and KM5PO

• W3SZ 1500 watts and 2 x 2 2MXP32
• KM5PO 1500 watts and 4x18XXX
• 144 MHz CW

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W3SZ EME Setup

• 2 x 2 2MXP32 Antenna Array with 21 dBd gain
• Homebrew Low Noise Preamps 2 less than 0.8 dB
  NF, placed approximately at the power divider
• Separate H and V receive feeds
• Linrad Receiver software and hardware WSE
• Elecraft K3 formerly FT1000MP Mk V
• Down East Microwave 28 MHz-144 MHz transverter
• LZ2US Amplifier 1500 watts out

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Linrad Demonstration
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MAP65

• Written by K1JT, directly integrates JT65B with
  Linrad
• Software combination is like CW Skimmer for
  JT65B, and automatically decodes all JT65B
  signals that are present in the pass band
  defaults to 60 kHz pass band

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MAP65 Example
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How does W3SZ Station perform?

• ARRL 2007 EME Contest
• Station as detailed above, including Linrad and
  MAP65
• Second Place Worldwide 144 MHz Single Band Mixed
  Mode
• 792,000 points
• 132 Total QSOs
• 118 Digital
• 14 CW
• 60 Multipliers

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EME on other frequencies

• 144 MHz is most active EME band, most common
  starter band
• 50 MHz is very difficult due to noise, antenna
  size requirements
• 1296 is next most common after 144 MHz
• 10 GHz is third most common
• As already noted, EME QSOs have occurred on every
  band from 28 MHz through 47 GHz

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Path loss vs frequency
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Antenna Gain vs Frequency K1JT
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Antennas

• 50 and 144 MHz yagi arrays, linear polarization
• 432 MHz yagi arrays or parabolic dish, linear
  polarization
• 1296 thru 3456 MHz parabolic, circular
  polarization
• 5 GHz and up parabolic, historically linear
  polarization Faraday rotation not a problem at
  these frequencies, now moving towards circular
  polarization

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50 MHz EME

• 6 Meters EME W7EW heard at SM7BAE

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SM7BAE8 9-element yagis on 63 foot boom
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1296 MHz SSB EME

• SSB EME IZ1BPN and PI9CAM, heard at PI9CAM
• IZ1BPN80 watts, 8 meter dish
• PI9CAM 60 watts, 25 meter dish

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IZ1BPN
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PI9CAM
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PI9CAM
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10 GHz EME

• 10 GHz EME WC8VOA heard at G4NNS
• WC8VOA 18 watts transmitter power, 7.2 meter dish
• G4NNS 18 watts transmitter power, 3.7 meter dish

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WC8VOA7.2 meter dish
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G4NNS3.7 meter dish
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24 GHz EME

• 24 GHz EME W5LUA, heard at PA0EHG
• PA0EHG 10 watts, 3 meter dish
• W5LUA 100 watts, 3 meter dish

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W5LUA 3 meter dish
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PA0EHG 3 meter dish
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47 GHz EME RW3BP
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Secrets for Successful EME

• Antenna gain--maximize
• Low noise receive preamp--at the antenna
• Attention to detail every dB counts
• Use lowest loss coax, lowest loss connectors,
  minimize number of connectors, minimize coax
  length, use low-loss high-isolation relays
• Transmit power--as much as possible
• Digital signal processing
• Patience
• Know when to operate!

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Getting Started
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W5LUA and VE4MA articles
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Down East Microwave
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SSB Electronics USA
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M2 Antennas, Rotors, etc.
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Directive Systems
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http//www.vhfdx.net/jt65bintro.html
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ARRL 2010 HandbookExcellent EME Chapter by K1JT