Cutting-edge diy projects
Achieved today something that I’ve wanted to do since I was a teenager: bounce a signal off the Moon. I was able to achieve that today for the first time!
Echoes were faint, but readable. Next, maximize power transfer to antenna and increase power to 600W.
This weekend I exchanged the LNA isolation relay by a transmit-type relay with N connectors, and replaced a short cable and N-to-SMA adapters by just two N adapters. This gave me one extra dB of Sun vs. cold sky. I then swept the position of the feed very carefully, but the best I could get was 9 dB of Sun noise.
KC2TDS (Jason) and I calculated the F/D of the dish to be around 0.45, which would mean that the septum feed would be OK as-is, but the dish’s manufacturer specs state its F/D at 0.37, although with inconsistent measurements. I decided to try a scalar ring to change the feed’s beam pattern in case that would be the reason for my low Sun measurements.
I cut out an 18″ diameter x 3″ deep “Fat Daddio” cake pan to allow the feed to protrude through the center. I reinforced the two sides of the orifice with frames cut of the waterjet. Two brackets hold the scalar ring firmly against the feed.
I am limited by the geometry of the struts, but was nevertheless able to gain 2 dB of Sun noise vs. cold sky (for a total of 11 dB) with this arrangement! ON0EME now comes in at approximately 5 dB above my noise floor, making for easy copy.
I also wired the TX port all the way to the nearby shed where the PA will reside, but didn’t get to wire the RX/TX relays, so trying to transmit and receive echoes off the Moon will have to wait until next weekend.
Sun Noise vs Cold Sky, and ON0EME copy with N2QG’s 12 ft dish
12 ft dish at N2QG with 1296 MHz septum feed and scalar ring.
After two weeks of battling with my receiver setup, I finally found the problem: The output stage of my home-brewed GPS-disciplined 10MHz reference was clipping on one side, which caused the AOR AR5000 to misbehave. My reception cleaned up as soon as I connected the rubidium reference instead of the GPS-locked source.
The feed is not optimized because I’m receiving only 8dB of Sun noise above cold sky, but this was nevertheless good enough to receive and clearly copy by ear the ON0EME beacon bouncing off the Moon.
Next: Optimize the feed and connect the power amplifier to start transmitting my own signals towards the Moon.
RS0ISS transmitted PD120 SSTV postcards December 28 2019 – January 1 2020 in memory of cosmonaut Alexei Leonov. I received the signals at 145.800 MHz using my new IC9700 rig and a M2 2MCP8A antenna. I did not use Doppler compensation, which accounts for some of the wobbliness. I used Nova for Windows to track the ISS.
Air Force Major General Alexei Leonov (1934 – 2019) was a Soviet and Russian cosmonaut, who in March 1965 became the first human to conduct a spacewalk. In July 1975, Leonov commanded the Soyuz capsule in the Soyuz–Apollo mission.
Click here for larger image.
I took advantage of the mild weather and holiday off time to install the 1296 MHz septum feed on the 12 ft dish.
Conditions are horrible right now for EME (the Moon is right next to the Sun), but I’m anyway still working on the power amplifier to make CW QSOs. So far all I have been able to do is to optimize the feed’s position using Sun noise. -3dB beamwidth is around 4 degrees, which is what I expected from this 3.5 m dish at 1.2 GHz.
The plastic box on the feed houses the RX isolation relay, LNA, filter, and cable driver. The feed is mounted using a modified RF Hamdesign CLX05 bracket, which connects to the struts via a universal-mounting bracket designed by KC2TDS:
A C/Ku Polarotor Feed is mounted 7 degrees from prime focus to aid in calibrating the antenna’s rotor controller against geostationary-orbit satellites. Here is the antenna pointing at the horizon, waiting for the next moonrise:
Left to right: Pedro Arzuaga, Assembled ÑuSat satellite, Jason Meyers, David Prutchi, and Julio Arzuaga at Satellogic’s assembly facility in Uruguay
Satellogic is an Argentinian company founded in 2010 specialized in Earth-observation satellites. Satellogic began launching their Aleph-1 constellation of ÑuSat satellites in May 2016, and as of September 2019, have launched 5 satellites in that series (Fresco, Batata, MilaneSat, Ada, and Maryam). We were invited to visit their satellite assembly facility in Zonamerica, near Montevideo, Uruguay.
Each ÑuSat weighs some 70 kgs (154 lbs) and are launched as secondary payloads on Chinese Long March 6 rockets. Once in orbit, these devices travel at 25,000 kph (15,500 mph) and take about 90 minutes to encircle Earth. With the on-board telescope, these satellites yield images with one-meter-per-pixel resolution, which is impressive given the small size and reduced cost of the satellites.
The assembly facility, led by Eng. Fabricio Borsellino, is a truly remarkable example of how a high-tech manufacturing site should be run. In a very short time Fabricio has managed to hire excellent personnel to conduct all of the activities required for the delicate process of assembling a satellite, and has been able to instate a culture of personal responsibility, ethics, and quality throughout the organization that will undoubtedly pay off as Satellogic’s demands for higher throughput grows.
Satellogic’s plan in the coming years is to maintain a constellation of 300 satellites. Each satellite has a mission lifespan of around 3 years, so the assembly facility in Uruguay is gearing up to manufacture 100 satellites per year for ongoing maintenance and renewal of the constellation.
ÑuSat satellite of the Aleph-1 series designed and operated by Satellogic
Artist conception by Dererk – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=56277284
Jason Meyers (KC2DSN) and I have been working on a circular polarization feed and downconverter to mount on the 12′ dish for X-band (8.4 – 8.45 GHz) amateur DSN reception (receiving signals from planetary probes using Deep Space Network frequencies).
The feedhorn is based on the dimensions of the one constructed by Michal SQ5KTM:
We used McMaster-Carr materials for our version of the feedhorn:
Jason KC2TDS carefully handcrafted the squeezed-tube depolarizer and built the feed:
We measured the feed’s gain, circularity ratio, and beamwidth at Microwave Update 2019:
Results were as follows:
Gain – 13.2 dB with a linearly polarized signal normal to polarizer inserts
Circularity: -2.5 dB with horn rotated 90 degrees
-3 dB Beamwidth: 33 degrees
S11: -18.5 dB at 8.45 GHz
We plan to place a Kuhne Electronic KU LNA (model 8000 B, 8000 to 8450 MHz, 28 db Gain,
0.8 dB NF @ 18 °C) right at the feed.
Measurements taken at Microwave Update 2019 showed a 0.9 dB NF and 29.5 dB gain at 8.45 GHz for our unit.
The LNA will feed the 400 – 450 MHz IF downconverter that we built:
We also tested the downconverter at Microwave Update 2019 and found that it has a measured noise figure of 4.58 dB and a gain of 24.4 dB.
Next step is to mount the setup on the dish and start experimenting with real DSN signals.
We’ll provide more details and updates as we continue working on this project.
I was cleaning up the basement, and found a box with my old pictures. This one brought me fond memories. This was my house (well, my parent’s house) in 1980. Back then my callsign was “HC1DT.” I had a TH3 on top of a tall tower, a 10m 3-element beam, and a bunch of home-made 2m verticals and beams.
As I had mentioned in the reflector discussion, my municipal permit allows my dish antenna to be up to 15 ft in diameter, so a project that will possibly precede the erection of the two towers is to expand the diameter of my EME dish from 12 ft to 15 ft. I’ve been looking at how other hams have done it, and I think that the following are the best examples of what I would like to do:
This increase in diameter should have a theoretical gain change from 11.3dB to 13.6 dB at 1296 MHz.
I would be interested in knowing any experiences by other hams who have modified their dishes for larger D. Anyone tried doing it to a Tek2000 dish?
I have received approval from the XYL for expanding my antenna garden, so I’m planning the projects for the upcoming fall and spring. NJ law allows me to put up a 70 ft tall tower (excluding the antenna) without interference from the township, so I’m planning to take it all the way to that height.
The tower next to the house can be supported against the outer wall of the house, and I’m intending to place a 6-element HF beam and a a large 2m/70cm EME array on top of that tower. My limitation is a 16 ft boom so that I can keep within 15 ft of my property line. That’s certainly enough for a large, high-gain array.
The second project is to elevate the current 12 ft microwave dish to expand my horizon. This will need a very heavy-duty, self-standing tower because of the wind load presented by the dish. I need to take some measurements and see what would be the best compromise between height and achieved minimum inclination, but I feel that will fall somewhere around the 30 ft range.
I’m currently looking at the specs of ROHN towers, and would love to hear feedback from current users under similar load conditions.
PS. Finishing the power amplifiers for 1296MHz EME right now… see you soon on the Moon at 23cm!