- The 50-foot EME Tower
- Looking up at the Tower
- The 144-MHz Array - QRV!
- Close up of EME Array
- Waiting for antenna support masts and antenna
- Four M2 2m-xpol-20 yagis waiting for installation (2.4m dish in background)
- EME yagis mounted, tested, and waiting for raising to tower top
- Another View of EME Array
Photos at the old QTH:
My array consists of four x-yagis mounted in the vertical/horizontal or "+" position. They are
model 2m-xpol-20's made by M2. The 12 by 12-foot"H-Frame" is also made by M2.
The array gain is 19.2 dBd (21.3 dBi) with this spacing. Using both vertical and horizontal
polarity gives my small, standard-sized, moon-bounce array the ability to adapt to
Faraday polarity shifts in the ionosphere.
The eme array is mounted on my custom-designed elevation bearing mount which utilizes a
satellite-dish actuator-arm (jack-screw). The azimuth mast is rotated with a Ham-IV rotator.
All is raised to the top of the 50-foot Rohn-25 tower on a Hazer H4 "cage".
This permits maintenance to be performed at ground level by lowering the cage and array.
The Hazer uses a hand winch and wire rope over a pulley at the tower top to accomplish this.
The 2-meter station consists of a Yaesu FT-847 all-mode transceiver followed by a
W6PO design 8877 linear amplifier that runs 600 watts output with a SWR of 1.06 at 144.100 MHz.
Approximately 415 watts is delivered to the antennas after taking into account cable losses.
The receiver is preceded by a preamp and four coax relays all housed in a weather-tight
enclosure attached to the Hazer cage. The vertical elements of each yagi are connected via
18-foot runs of Times LMR-400 coax cable to a M2 4-way divider. A 10-foot LMR-400UF
jumper connects the divider to the vertical polarity T/R relay (K1) with one port feeding the V-pol
port of a sma relay (K4) that precedes the mgf-1801 preamp (0.15 dB Noise Factor, 16.8 dB gain).
In a similar way the horizontal elements of each yagi are fed to an identical T/R relay (K2) and to
the H-pol port of the preamp relay. T/R logic switches the preamp sma relay to the polarity
opposite that of the Tx polarity relay to maximize isolation from high power RF during
transmission.
The transmit ports of both the vertical-pol. T/R switch and the Horizontal-pol. T/R switch
are connected to a third coax relay (K3) that choses which polarity is used in transmiting.
This is then connected via 7/8-inch hardline to the transmiter amplifier in the radio room.
The preamp is followed by LMR-400 feedline with 1.5 dB loss. In the radio shack a
DCI-145-2H bandpass filter precedes a line amplifier (ARR 144VDA - 1 dBNF, 14 dBG)
which feeds the FT-847 Rx antenna connector.
With this receiver system I may chose transmit and receive polarity independently for
four choices: H/H, V/V, H/V, or V/H, thus providing me good match of reception for
whatever polarity signals are received back from the Moon. This system will eventually be
replaced with a dual matched preamps feeding a continuously variable polarity control unit.
I estimate my overall system NF is about 0.80 dB.
January, 2007 - Update:
I am building a 144-MHz to 28-MHz transverter to be used with the new SDR-IQ receiver board
producing a 190-KHz wide spectral display. New software under development by K1JT called MAP65
combines the properties of Linrad and JT65. Using the SDR-IQ as input to MAP65 will provide me
full coverage of the 2m EME sub-band using random JT65 operation. This is new technology still
under development.
144-MHz EME Station Block diagram.
2M-EME QSL cards
- 1999 QSL
- 2004 QSL
- New Card For 2007
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