Presentation on theme: "Gary Sutcliffe, W9XT Ken Boston, W9GA Copyright Gary C. Sutcliffe 2011"— Presentation transcript:
1 Gary Sutcliffe, W9XT Ken Boston, W9GA Copyright Gary C. Sutcliffe 2011 Moon Bounce For QRPersThis presentation was made at the Amateur Electronic Supply Superfest on April 2, 2011.It was streamed live, and the recording can be viewed atMaking contacts via the moon with a modest amateur 2 meter stationGary Sutcliffe, W9XTKen Boston, W9GACopyright Gary C. Sutcliffe 2011
2 EME (Earth-Moon-Earth) EME involves transmitting a signal towardsthe moon and receiving the reflected wave.This allows worldwide contacts on frequencieswhere contacts are normally line of sight only.
3 EME Factoids Average distance to moon ~240,000 miles Moon apparent size ~0.5º2.4 second radio signal round tripMoon reflects only ~7% of signalAverage 144 MHz path loss: ~250 dBThe 250 dB path loss is really what makes EME difficult.
4 What is 250 dB?Ratio of 10,000,000,000,000,000,000,000,000 : 1Difference between1KW and 0.1μW is only 100dB, 2KW and 0.1μW is 103 dBYou could make a 250 dB attenuator for 2M with 3.14 miles of LMR 400 CoaxIf US power grid had these losses, you would have to multiply the total generating capacity by 10 Billion to get one watt out250 dB is one of those numbers that are hard to grasp. Sort of like the federal deficit.DB are logarithmic. 1 KW to .1 uW is 100 dB. 2KW gives 103 dB, 4 KW gives 106 db, etc.Each time you double power or halve losses, you only gain 3dBBut wait! It gets worse!
5 Complicating Factors Moon moves Need to move antenna AZ/EL to trackDoppler shift in frequencyDistance variation adds additional lossesIonospheric absorption can add more lossFaraday rotation skews polarizationCosmic & solar noise interferes with signalThe moon’s distance can vary by nearly 30,000 miles, increasing loss by several dBFaraday rotation occurs as signal goes through ionosphere. If your antenna is horizontal and the signal is rotated to vertical, you won’t hear it.S/N ratio is everything. Some sky areas are noisy and can cover up weak EME signals. EME is usually not attempted at new moon, when the sun and moon are in the same part of the sky.The combination of distance and noise can degrade path by more than 10dB over optimum conditions.EME may be the biggest technical challenge in Ham Radio!
6 Overcoming the Obstacles High powerBig antennasLow loss coax, good connectors, etc.Low noise receivers & pre-ampsSpecial techniquesW9GAYou need to sweat the details in an EME system. Many contacts are right on the edge. Every dB matters.
7 System Loss Calculations GainLossPower outTransmit antennaReceive antennaReceiver gainTransmitter feed line lossPath lossReceiver feed line lossW9GASum of the gains minus the sum of the losses must overcome the noise.Each stage increases noise.Can’t just use a lot of RX gain. Noise picked up along the way will be amplified along with the desired signal.Σ(gains) – Σ(losses) > Noise
8 EME Bands6M - Once thought to be impossible because of antenna size, but gaining popularity2M - Most popular band mostly because of availability of equipment432 & 1296 MHz - Most popular after 2M. Lower noise levels but not much commercial equipment available.Higher microwave bands are for the really dedicated EMEers.
10 Photo courtesy of Dave Blaschke, W5UN W9XT(W5UN) only a few stations in the world this big, but are a starting point for the first EME QSOsPhoto courtesy of Dave Blaschke, W5UN
11 KJ9I W9GA Photo W9GA 8 cross polarized Yagis No longer up – Dave worked 2M DXCC with thisA few dozen stations this size worldwide – very workable by small EME stationsW9GA Photo
12 W7IUV Left: 8 X 8 Element, 2M Right: 7’ dish, 1296 MHz W9GAA lot of the 1296 and higher EME stations use obsolete TV dishes.Photos courtesy of Larry Molitor, W7IUV
13 W9XT’s “QRP” EME Station Equipment:Yaesu FT-847 All mode transceiverMirage B2518G 150W 2M ampCushcraft 13B2 13 element Yagis (2)CATV 75Ω hardlineDell PC running XPUnified Microsystems SCI-6 PC I/FThe tower is only about 20’ high. Two phased Yagis have about 3 dB more gain than a single Yagi.The tower is about 80’ from the house. 75 ohm CATV hardline is used because of its low loss. It is cut a multiple of 1/2 wave so the 50 ohm input impedance is reflected as 50 ohms at the other end.Is moon bounce possible with such a small station?
14 W9GA’s EME Station Equipment: Kenwood TS-711 2M All mode transceiver Henry M KW amp2 X 9 el M2 Yagis, hand aimed (not shown)M2 preampLaptop PCW
15 K1JT’s WSJT Program WSJT – “Weak Signal Joe Taylor” Free PC Program Uses special DSP techniquesModulation optimized for weak signal modesDig out signals deep in noiseJT-65 optimized for EMELow data ratesSingle tone per characterNarrow bandwidthDecode calls to about -28dB, reports to about -30dBJT65 lowers the bar. It has at least a 10 dB advantage over CW.Trained CW ops can copy low speed CW about 14 dB below noise. JT65 decodes near 30 dB below noise are possible.-28 dB corresponds to signal strength below unity in a 2500 hz bandwidth, (SSB)
16 K1JT WSJT – JT65 ModeUpper right blue box: Shows moon coordinates Doppler shift, and path degradation. This screen created with play back of recorded signal. The moon was not below the horizon when the contact made!Upper graph: Green line signal. You can only see noise.Red line shows synch signal decode. Nice spike in center of screen is what you want.Blue curve shows the delta time. It is were it should be, about 2.4 seconds. If it is not, the PC clock at one station is not set right. If at far left, it could be signal is direct line of sight, not EME.Decode box:Sync = 6. That is good. Want to be at least 1 or 2. Higher is better.dB = -23. Signal is 23 dB below RX noise. A strong signal!DT = delta time. 2.3 seconds. Means PC clocks are set correctly and signal is via moon.Decode: W9XT DK1CO JO63 - DK1CO in Germany is calling W9XT and including his grid square.Center Bottom: Controls to aid in decodesBottom right: Pre-generated messages for each transmission sequenceBottom center: RX noise 0dB – RX noise level should be adjusted to 0dB
17 SpecJT Waterfall Screen Shot The light vertical line is the sync signal. On the actual screen the resolution would be better and some other white specs from other parts of the signal would be visible between 1400 and 1750.Signal Received: DL5BBW ES3RF KO29 OOOSignal -22dB – A strong one!
18 JT65 EME QSO Sequence Stations alternate 1 minute transmissions: Station 1 Transmission Station 2 TransmissionCQ W9XT EN53W9XT DX1XX ZZ99DX1XX W9XT OOORORRR73W9XTQSOs follow a strict sequence to ensure proper information is sent and received. In this example W9XT is calling CQ.DX1XX copies the CQ and calls W9XT and includes his grid square (optional)W9XT continues to call CQ until he copies both calls. When both calls are copied W9XT replies with both calls and signal report ‘O’. That is a carryover from CW EME which uses the TMO system instead of RST. O means both calls copied correctly.When DX1XX copies both calls and the signal report he responds with RO which means he copied both calls and signal report and is giving his signal report of O.W9XT continues sending both calls and signal report until he copies RO. Then he starts sending RRR which means he acknowledges copying his signal report. The QSO is now official.Station 2 usually sends 73 to acknowledge receipt of the RRR transmission.Many QSO attempts are arranged by schedules or on the Internet. In that case both stations start with both call signs and grid square. When the first station copies the other they switch to call signs and signal report and the regular sequence starts.Each station transmits the current sequence until it receives the full response.
19 Many EME QSOs are scheduled on Ping Jockey W9XTMany EME QSOs are scheduled on Ping Jockey
20 EME Results W9XT ~ 40 QSOs ~15 DXCC countries W9GA Approx 50 QSOs EME QSOs are possible with a modest station. W9XT & W9GA contacts made since December 2009.Results CW vs JT63There are several dozen big EME stations capable of working 100 watt single Yagi stationsThese stations are always looking for new stations to add to their “initial contact” list
21 “Life is too short for QRP” W9XT future station plans4 Yagi arrayAmplifier with pair of 4XC250’s (~600Watt)Goals2M WAS (37 states worked, most terrestrial)DXCC (14 countries worked)A small station can only work larger stations. Most of the contacts are with stations running 1KW and 8 or more Yagis. New stations to work are not too common.A station running 1 KW and 4 good size Yagis can work similar stations under good conditions. There are hundreds of such stations world wide.
22 Minimum EME Station Plus a big gun station at the other end! Long horizontal YagiSSB transceiver w/100 wattsPCPC sound card interfaceWSJT ProgramWork at moon rise/setGet about 6 dB ground gainDon’t need elevation rotorMany VHF stations are capable of EME even though the owner does not realize it.W9XT’s first two EME contacts were made with a single 13 element Yagi (2nd from top in picture) and 100 Watts at moon rise. In a contact with W5UN, the amp died in the middle of the QSO, and it was completed with only 50W!With a station like this, a big station at the other end is required.There are several dozen stations with the 4+ yagi & KW that can be worked with this stationHorizon only, moonrise and moonset, can be hard if noise is present in neighborhood.Plus a big gun station at the other end!Are you able to do EME with your station?
23 EME Resources WSJT Download: www.physics.princeton.edu/pulsar/K1JT/ N0UK Ping Jockey page:DF2ZC 2M EME Newsletter:NewsDXpedition schedulesBest condition calendarUnified Microsystems:Inexpensive PC sound card to radio interface kit
24 Acknowledgements Moon and Earth Images: NASA Goldstone Antennas: NASA Station and antenna pictures:Dave Blaschke, W5UNLarry Molitor, W7IUVThis presentation will be posted atQuestions
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