Cutting-edge diy projects

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Cutting-edge diy projects

Monthly Archives: April 2020

First light on S-band with low-gain (1.2m) offset dish

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(c)2020 N2QG David Prutchi PhD log-periodic feed for 1.2m offset dish

I have the aiming of the 1.2m offset dish calibrated, so it’s ready for receiving on DSN bands.  I started by placing a WA5VJB wideband log-periodic array at the focal point followed by a Minicircuits LNA.  I placed the filter/cable driver in the mast box to send the S-band signal via 100 ft of LMR400 to the shack.

With the Az/El under the command of NOVA for Windows, I set it to track DSP-F21 (USA-159).  The satellite transmits using circular polarization, so I know that I’m wasting at least half of the signal by receiving with linear polarization, but this is the feed that I have on hand for this antenna.  Nevertheless, the received signal is very clearly seen against the low noise floor:

US Air Force’s Defense Support Program (DSP) which operates the Satellite Early Warning System. The TLEs for this satellite (USA-159) are distributed by SpaceTrack. The satellite was launched in 2001 and is still used for missile launch detection. The satellite emits a constant carrier at 2237.5 MHz

Next:  Mount the DSN x-band horn/lna/downconverter on the 1.2m dish and start to practice tracking of non-Earth-orbiting probes.

 

 

 

 

Decontaminating N95 Masks at Home to Extend their Use During CoVid-19 Pandemic

Posted on by Posted in d.i.y. Medical Devices, David

N95 Mask disinfection resterilization at home using UV (c)2020 David Prutchi PhD

Remember that book that I wrote on UV Photography?  Well, I ended up collecting/building a number of UV lamps, and some of them emit UV-C.  I set them up as a makeshift decontamination rack for our N95 masks.

The effectiveness of using germicidal (UV-C) light to decontaminate N95 masks to extend their useful time is well established.  In fact, use of Ultraviolet Germicidal Irradiation (UVGI) has been recommended as an emergency measure by the CDC.  The limiting factor is that UV-C degrades polymers, so it will eventually cause failure to the mask’s structural integrity (Lindsley et al, 2015).

Our protocol at home, based on my understanding of CDC’s guidelines and the intensity of my lights is to use masks for up to 8 hours (of actual use time when outside of the house grocery shopping or running essential errands) and then expose them for 15 minutes per side to UVGI before reuse.

The link to my DIY Long/Med/Short UV lamp is available here. Or in whitepaper format here.

IMPORTANT NOTE:  This post should not be construed as advice on the decontamination of PPE.  Please refer to official information on this matter from the CDC.

WARNING:  Midrange and short-wave ultraviolet radiation can cause permanent eye and skin damage.  Do not look directly at midrange or short-wave UV radiation, even for brief periods. Take appropriate precautions with pets and other living organisms that might suffer injury or damage due to UV exposure at these wavelengths.

 

Exploring Ultraviolet Photography book by David Prutchi PhD.

 

Defense Support Program (DSP) F21 2237.5 MHz Carrier as it Orbits

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

DSP F21 carrier throughout the night (c) 2020 David Prutchi PhD N2QG

Click here for high-resolution version of the image.

DSP-F21 is a satellite of the US Air Force’s Defense Support Program (DSP) which operates the Satellite Early Warning System.  The TLEs for this satellite (USA-159) are distributed by SpaceTrack.  The satellite was launched in 2001 and is still used for missile launch detection.  The satellite emits a constant carrier at 2237.5 MHz which sometimes becomes active with data during Early Warning and LEO SIGINT operations.

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Adding an External Frequency Reference Input to the RFspace SDR-14

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RF Space SDR-14 Modified by David Prutchi PhD N2QG (c)2020

My favorite microwave receiver is the AOR AR5000.  I have it locked to either my 10 MHz rubidium or GPS references.  The 10.7 MHz IF output goes to an RFspace SDR-14 which I display using SpectraVue.

The SDR-14 does not come with a provision for feeding an external reference, but I know I had seen something about this a long time ago.  I Googled it, and found out that Dave Powis, G4HUP, the originator of the mod had become SK.  His web page is no longer active, but found it using WayBackMachine.

I successfully modified my SDR-14 and am feeding it 66.666,666 MHz from a Leo Bodnar Mini Precision GPS Reference Clock.

Click here for my writeup of the mod with pictures, as well as Dave’s original posting.

Link: N2QG RFspace SDR-14 GPS Lock

S-Band DSN (and Aerospace L-Band Telemetry) RX LNA and Filter Front-End

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

Block diagram of DSN S-band and aerospace telemetry L-band front-end (c)2020 David Prutchi PhD N2QG

The CoVid-19 quarantine has given me the opportunity to revisit neglected home projects, so I decided to add another Az/El dish to my antenna garden.   The main purpose of this new dish will be to serve as a low-gain testbead before moving an experiment to the 3.5 m dish.

My first experiment for the new dish will be on S-band DSN, especially to “learn the ropes” about tracking non-terrestrial-orbiting probes before I try it on the high-gain dish.

The S-band DSN frequencies are as follows:

Deep Space S Band Frequencies

The downlinks require the receiver to operate between 2200 and 2300 MHz.

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