Amateur DSN – Page 2

The EchoStar RV-750 “Umbrella” (Collapsible) 7.5ft TVRO Antenna

Posted on July 13, 2020 by David Prutchi Posted in Amateur DSN, Amateur Radio N2QG, David

I’ve been planning ahead to the day when I retire, my girls live on their own, and my wife and I can finally take the big-RV roadtrip that we’ve been talking about forever. Not being one for sitting by a campfire, I’m always collecting equipment to take along, and some time ago my ongoing eBay® search for a collapsible parabolic antenna hit gold. It was for an EchoSphere 7.5 ft TVRO folding dish in mint condition. It even came with an extra (slightly damaged) reflector assembly to boot! My plan is to build feeds for 1296 MHz EME and S-Band DSN. Sadly, 10 GHz EME and X-band DSN are out of range for the reflector’s fabric.

The EchoStar RV-750 comes in a carry bag. It can be assembled and deployed in lessa than 10 minutes (c)2020 David Prutchi PhD N2QG

Finding information on this dish has been much more difficult than I had anticipated. I summarized my literature and experimental findings in a short write-up available at: The EchoStar RV-750 Antenna by N2QG Continue reading→

Diagnosing X-Band DSN and again QRV EME 1296 MHz

Posted on July 5, 2020 by David Prutchi Posted in Amateur DSN, Amateur Radio N2QG, David, Earth-Moon-Earth, Satellite hunting

BepiColombo spacecraft received by N2QG 5 July 2020 Amateur x-band DSN (c) David Prutchi PhD

I moved the X-band setup to the 1.2m offset dish to be able to characterize and diagnose. The problem is that I’m unable to get the system mounted on the 3.5m dish to yield the signal levels that I’m expecting. I’m suspecting surface accuracy because the 3.5m dish behaves well at 1296 MHz, but the g/t is just not there at 8.45 GHz.

I can receive BepiColombo on the 1.2m dish with around 12 dB compared to 16dB on the 3.5m dish. However, M0EYT receives it at around 30dB on his 2.4m prime dish.

Is it time for my garden to grow a new large solid dish?

Strong Signal from OSIRIS-REx Received at 8445.538 MHz

Posted on June 21, 2020 by David Prutchi Posted in Amateur DSN, Amateur Radio N2QG, David, Satellite hunting

One more beautiful trophy for this weekend: Great signal received from the OSIRIS-REx spacecraft after M0EYT kindly told me how to find its ephemeris (hint: it’s orbiting around asteroid Bennu).

OSIRIS-REx is NASA’s first asteroid sampling spacecraft. It’s currently orbiting asteroid Bennu on its 7-year mission to return a pristine sample from that asteroid.

Mars Reconnaissance Orbiter (MRO) Received

Posted on June 21, 2020 by David Prutchi Posted in Amateur DSN, Amateur Radio N2QG, David, Satellite hunting

Another Martian probe in my bag: Mars Reconnaissance Orbiter (MRO) this morning received at 8439.6638 MHz while locked to Goldstone.

The following is from MRO coming out from behind Mars and being re-acquired by Goldstone:

MRO coming out from behind Mars received by N2QG (c)2020 David Prutchi, PhD

DSN X-Band Feed Tweak

Posted on June 20, 2020 by David Prutchi Posted in Amateur DSN, Amateur Radio N2QG, David, Satellite hunting

Today I tweaked the position of the feed and the VE4MA ring on the 3.5m dish. Signals improved quite a bit, with STEREO A at 9dB above noise, and BepiColombo at 15dB above noise. However, there is still quite a bit of room for improvement. I had to take down my measurement setup when the “severe thunderstorm” alert came in. Will try again tomorrow.

N2QG DSN X-Band Downconverter

Posted on June 15, 2020 by David Prutchi Posted in Amateur DSN, Amateur Radio N2QG, David, Satellite hunting

CLICK HERE for high-resolution image.

Lately I’ve been asked about the downconverter that I built to receive X-band DSN signals. Because of time limitations, I took some shortcuts, namely using commercial connectorized modules and a high-stability signal generator with integrated mixer (DS Instruments MX12000 Integrated-LO Mixer) instead of designing the circuit from scratch. The cost of the unit is thus relatively high, but it was either that or not being able to receive X-band spacecraft at all in the foreseeable future.

We tested the downconverter (without LNA) at MUD2019, and measured a 4.58 dB noise figure and a downconversion gain of 24.4 dB.

VE4MA Feed Mounted on 3.5m Dish and First-Light with RX of Mars Express

Posted on June 14, 2020 by David Prutchi Posted in Amateur DSN, Amateur Radio N2QG, David, Satellite hunting

Yesterday I mounted the VE4MA with squeezed-tube depolarizer made by M0EYT (uhf-satcom) on the 3.5m dish using a bracket designed and fabricated by KC2TDS. The tube holder is 3D-printed nylon, while the bracket itself is aluminum cut with water jet.

It got late by the time I finished mounting the feed, so I didn’t have time to optimize the position of the feed and super Kumar ring relative to the focal point. Nevertheless, measured 11dB of Sun noise vs. cold sky.

This morning, before Mars would set, I was able to receive the Mars Express spacecraft. I could see on DSN Now that it was locked to Goldstone.

Fading in the signal shown below was because I still have to tweak PstRotor and the rotator controller (Green Heron) driving the BIG-RAS Az/El to deal with the very narrow beamwidth (0.69 degrees) produced by the 3.5m dish at X-band.