W7GJ PORTABLE 6M EQUIPMENT

The following are details of the portable 6m station used since VK9CGJ and VK9XGJ 6m EME DXpeditions in 2017.  Focus has been on providing the most sensitive receive station possible along with the most reliable and efficient - while compact and light weight - amplifier and power supplies.

ANTENNA: I use an M2 6M8GJ  yagi mounted on an M2 24' Portable Mast . At the beginning of 2020, I built a new lighter weight manual elevation mount that allows me to elevation the antenna to aim it at the moon as it moves across the sky and I successfully used this mount starting in the 2021 DXpeditions to FO. There is a complete description of how I put together the antenna and mount, and how I raise it into position, along with photographs of the antenna in operation here. Here is a short video showing me raising the assembled antenna when I was operating from Palau in 2016. You can see from the video why it is important for me to try to find a place to set up where I have enough open space to raise the antenna easily. Here is a photo showing the antenna installation in Nauru in 2018, which was erected and operated in a much more challenging confined space than I usually try to find.

FEEDLINE: I use Times Microwave LMR-600 Coaxial Cable with type N connectors between the antenna and the station in order to keep the feedline loss well under 1 dB. This is essential because the signals coming back from the moon are very weak (and rarely audible to the human ear) and it is essential to try to capture as much of the signal as possible before they reach the receiver preamplifier. I try to use as short a piece as possible, but much of that depends on the site where I am able to set up the station and antenna. In Nauru during 2018, in Bolivia in 2019, and in both FO DXCC during 2021, the antenna was close enough to the station to allow me to use only 50' of LMR-600 Ultra Flex. In 2017 in Cocos/Keeling Islands and Christmas Island, I had to use closer to 120', to reach an open area large enough for the antenna. I always take 50' of LMR-600 Ultra Flex to connect to the antenna, since it accommodates the flexing around the elevation mount and guy lines.  When I am going to need extra feedline, I usually take a 25' piece of standard LMR-600, which is lighter weight than the Ultra Flex, to extend the feedline to reach to the equipment.  I also take a pair of four foot long pieces of LMR-600 and a pair of four foot long pieces of LMR-400 to use as interconnecting cables for the equipment and/or to further extend the feedline if necessary.

TRANSCEIVER: To generate the RF signals on 50.190 MHz, for most DXpeditions, I used a Yaesu FT-857 amateur radio transceiver. I have modified it slightly as shown here, to provide an output to automatically turn on my 50 MHz amplifier. Starting in 2022, I am using a QRP FDM-DUO SDR transceiver.

AMPLIFIER: On most DXpeditions, I have used an M2 Inc. 6M1K2 amplifier to boost the maximum 50 MHz output from my FT-857 transceiver to 1000 watts output. Due to the low duty cycle of digital mode (transmitting only around 50 seconds during each 2 minute period), and the additional attenuation due to coaxial cable feedline loss to the antenna, the average power output at the antenna typically is around 350 watts when aimed up at the moon.

Starting in 2022, I am using a special DXpedition amplifier custom made by DX Shop. This particular amplifier requires about 3w drive for 1500w output. It requires 57 VDC input and provides up to 4A at 11 VDC that can be used to power my FDM-DUO transceiver, my Airspy R2 receiver and my external preamplifier.

WATTMETER: The amplifier output power and antenna match had been monitored with a Daiwa CN-501 dual needle wattmeter. I also have the option of using a Bird wattmeter element and remote meter.

PREAMPLIFIER: To boost the received signal, I use an ARR MSP50VDG RF-switched preamplifier that I modified to provide output to a separate receiver.

COMPUTER INTERFACE:  A RIGblaster Plug & Play  interface is used to cleanly connect the audio tones generated by the digital modes in the WSJT-X program in my computer to modulate the USB signal of my FT-857 transceiver. The FDM-DUO has a built-in computer interface with three USB cables.

RECEIVER: The separate receiver I used before was a USB RTL Dongle (NooElec NESDR SMArt - Premium RTL-SDR w/ Aluminum Enclosure 0.5PPM TCXO ). A small 50 MHz bandpass filter from Down East Microwave was used ahead of the RTL Dongle to prevent overload from out of band signals. The output of the SDR receiver is processed by the computer program SDR-Console Version 3. The output from the SDR-Console program is sent via Virtual Audio Cable to the WSJT-X computer program to decode the incoming digital signals. I have now replaced the RTL-Dongle with an Airspy R2 receiver, which has greater dynamic range, but everything else in the setup is exactly the same as before.
 
SOFTWARE: For EME, I now use Q65-60A mode from the most recent WSJT-X software package. There are several reasons for using this version:

    1. Q65-60A in WSJT-X is slightly more sensitive on very weak signals than the JT65A and many of the signals I am trying to decode with my small 6m EME station are very weak!
    2. The "Wide Graph" in WSJT-X provides large display of the bandpass and since Q65 is half the bandwidth of JT65A, this makes it easier for me to spot callers who are spread out more widely.
    3. Starting with WSJT-X version 2, there is a 64 bit version, which decodes much more quickly on my 64 bit Windows 10 laptop.

COMPUTER: My computer had been an MSI GP72 7RDX Leopard  17" laptop running a Windows 10 64 bit operating system. Starting with S79GJ in 2019, I was forced to go with something more compact, so I got a DELL XPS-13 9370. It has more than high enough resolution on the screen for the WSJT-X WIDE GRAPH and is fast, with an Intel 8th generation Core i7 processor. It also has two free USB-C ports while plugged in, so I can connect a bank of external USB ports to accommodate my Airspy R2 USB receiver as well as the FDM-DUO transceiver.

POWER SUPPLIES: When I have access to 230 VAC, I use a Meanwell RSP-3000-48  switching power supply to provide the DC voltage required by the amplifier.  When I used the FT-857, I used a  PowerWerx SS-30DV 110/220 VAC switching power supply to provide 12 VDC for the transceiver and preamplifier.
The 50 VDC from the power supplies was connected to the 6M1K2 amplifier via a twisted pair of #8 stranded copper wire cables, attached to the #10 pigtails coming out of the amp using a 50A battery cable connector (NAPA #740234, like a really big Anderson Power Pole connector).  After connection failures in VK9 with the standard Yaesu 12 VDC molex power connector plug, I  used a NAPA #740234 for my 12 VDC connection to the FT-857.  In locations where I have only access to 110 VAC, I use a pair of Meanwell RSP-2000-48 connected in parallel.  These Meanwell RSP-2000-48 power supplies provided by the DX Shop are specially prepared to be able to handle full power for the duration of the JT65 transmissions.

The special DX Shop DXpedition amplifier requires 57 VDC, which is provided by the Meanwell power supplies. It also includes a built-in 12 VDC supply to power the FDM-DUO and my external preamplifier to the separate 12 VDC power supply is no longer needed.

OVERALL STATION SETUP: I also use ferrite filters on all computer and power leads to prevent RF pickup/generation. Here are photos of my station as described above, completely set up when I operated moonbounce on 50.190 MHz from Nauru in 2018 and Seychelles in 2019.

Revised 3 March, 2022