Cutting-edge diy projects

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Cutting-edge diy projects

Category Archives: Amateur Radio N2QG

Taking Orders for Canadian Geese Microwaved On-The-Fly ;)

Posted on by Posted in Amateur Radio N2QG, David, Earth-Moon-Earth

N2QG 1296MHz 600W power amplifier (c) N2QG David Prutchi Ph.D.

This weekend I was able to combine the power of two 320W pallets using ring hybrid couplers (rat races) for an output of around 600W.  The strength of my own CW echoes improved dramatically.  The setup above still needs cleanup, and I may end up placing it at the base of the antenna to reduce cable losses.  On the meantime however, my system is ready for CW QSOs.

A number of stations calling CQ this afternoon at 1296.020. (c)2020 N2QG David Prutchi PhD

Conditions were good today, and there were quite a few stations calling CQ off the Moon.  Unfortunately, I realized how rusty my code has become, and cheating by using decoding software does not help at these signal levels, so I decided to hold off on answering until I get my code back up to speed.

JT65-C decode by N2QG

I also started playing with JT65.  I can decode straight from both the IC-9700 and the AOR AR5000/SDR14.  Next weekend I’ll build a circuit so that the computer can trigger the PA sequencer to be able to TX JT65C.

 

Scalar Ring for the 1296 MHz Septum Feed

Posted on by Posted in Amateur Radio N2QG, David, Earth-Moon-Earth

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.

 

First 1296 MHz Signals Received Off the Moon with 12 ft Dish

Posted on by Posted in Amateur Radio N2QG, David, Earth-Moon-Earth

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.

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:

 

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!