Cutting-edge diy projects

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Cutting-edge diy projects

Category Archives: David

ARISS SSTV Event Received with IC9700

Posted on by Posted in Amateur Radio N2QG, David

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.

1296 MHz Septum Feed Installed on 12 ft. Dish

Posted on by Posted in Amateur Radio N2QG, David, Radio Astronomy

1296 MHz septum feed for EME mounted on 12 ft dish. (c) 2019 N2QG David Prutchi, Ph.D.

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:

 

Visit to Satellogic’s Satellite Assembly Facility in Uruguay

Posted on by Posted in Amateur DSN, David, Travel
Visit to Satellogic's satellite assembly facility (c)2019 David Prutchi PhD www.prutchi.com

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

 

 

N2QG/KC2TDS X-Band Amateur DSN Project

Posted on by Posted in Amateur DSN, Amateur Radio N2QG, David

Jason Meyers (KC2TDS) 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:

IMPORTANT UPDATE 1 June 2020: Please see https://www.prutchi.com/2020/06/01/probe-location-for-squeezed-tube-x-band-dsn-feed/ for the correct probe orientation!

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.

 

My Childhood QTH

Posted on by Posted in Amateur Radio N2QG, David

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.

Expanding the 12 ft EME Dish

Posted on by Posted in Amateur Radio N2QG, David

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?

 

 

 

 

Antenna Garden Expansion Plans at my QTH

Posted on by Posted in Amateur Radio N2QG, David

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!

Modifying a Tek2000 12ft Dish for Az/El Rotation with a SPID BIG-RAS Rotator

Posted on by Posted in Amateur Radio N2QG, David, Radio Astronomy

I am now concentrating the bulk of my ham activities in the microwave region, and have CW EME and amateur DSN as my top projects. My goal was thus to install a relatively large prime-focus dish to be moved by a heavy-duty Az/El rotator.

In this whitepaper I describe how I modified a Tek2000.com 12 ft TVRO mesh dish so that it can be moved by a SPID BIG-RAS Az/El rotator.

Location of whitepaper:  Tek2000 antenna on AzEl – N2QG

 

 

Using the Trivec-Avant AV2040-2 Military Wideband SATCOM Antenna in the Amateur Radio Bands

Posted on by Posted in Amateur Radio N2QG, David

It’s July 20, 2019, and I am invited to a private screening of the CNN Apollo 11 documentary, followed by a party with my fellow nerds, so I don’t really have time today to work the sats. It’s 102ºF outside, so not a good day to tweak the antennas either, but I nevertheless wanted to do something space-related to celebrate the 50th anniversary of the Apollo 11 Moon landing.

As a compromise, I decided to test a Trivec-Avant AV2040-2 SATCOM antenna indoors to see if it would be suitable as a portable antenna in the VHF and UHF ham bands.

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Published data are NOT protected by copyright!

Posted on by Posted in David

I was cleaning my desk today, and came across a folder containing correspondence about a legal threat that I received a few years ago from someone accusing me of copyright infringement.

The accusation was that I had used his published data in one of the figures in one of my books without his permission, and had thus violated his copyright.

For my figure, I had drawn a stylized graph which matched the data presented in his graph, but I didn’t copy his figure.  He acknowledged the fact that I had “changed the colors and style,” but insisted that the fact that he had placed a copyright notice meant that the data were his, and that anyone publishing a graph that matched these data would be infringing on his copyright.

Although presenting and contrasting previously published data are the basis for academic discussion, which is why it didn’t even cross my mind that I would be doing something unethical or illegal by presenting my version of the graph, I wanted to make sure.  Indeed, I was right – in the US, as in most parts of the world, ideas, procedures, and data that can be independently retrieved or replicated (i.e. which are not specific to the subjective viewpoint of their creators) are not subject to copyright.

I also checked with the European Copyright Code, which states that the following are not to be regarded as “expressions within the field of literature, art, or science” that can be protected by copyright:

  • Facts, discoveries, news, and data;
  • Ideas and theories;
  • Procedures, methods of operation, and mathematical concepts.

Furthermore, hearings regarding the US Database and Collections of Information Misappropriation Act of 2003 show that data are not protected under copyright.  It is clearly stated that while certain databases may qualify for copyright protection if they exhibit some modicum of creativity in the selection, arrangement, or coordination of the data, in no case are the data themselves copyrightable.

Bobby Glushko, now the Head of the University of Toronto Scholarly Communications and Copyright Office wrote a very nice article about this very question while the Copyright Program Manager at the University of Michigan.  The article is available online at:

https://deepblue.lib.umich.edu/bitstream/handle/2027.42/83329/copyrightability_of_tables_charts_and_graphs.pdf

Based on the explanations in the article, even if I had taken each single point of data in his chart, and just because it took him effort to acquire these data, it doesn’t mean that the data are subject to copyright protection.   This is because:

“Facts, data, and the representations of those facts and data are excellent examples of things that require much “sweat of the brow” to create, but yet still do not receive copyright protection.”

Please note that I’m not a lawyer, so don’t take any of the above as legal advise.  However, I hope this will be a good starting point for anyone who is threatened by a bully with a false claim of misappropriation of intellectual property based on use of published data.