NASA Seeks Ham Operators For Sun Data Capture

I just saw a link to this article come across the HAMRADIOHELPGROUP. NASA will be collecting data from two observer satellites on either side of the sun and would like the help of ham radio operators to collect the data on 10m. Anyone with a 10m dish antenna is welcome.

"St. Cyr notes that experienced ham radio operators can participate in this historic mission by helping NASA capture STEREO's images. The busy Deep Space Network downloads data from STEREO only three hours a day. That's plenty of time to capture all of the previous day's data, but NASA would like to monitor the transmissions around the clock.

"So we're putting together a 'mini-Deep Space Network' to stay in constant contact with STEREO," says Bill Thompson, director of the STEREO Science Center at Goddard.

The two spacecraft beam their data back to Earth via an X-band radio beacon. Anyone with a 10-meter dish antenna and a suitable receiver can pick up the signals. The data rate is low, 500 bits per second, and it takes 3 to 5 minutes to download a complete image.

So far, the mini-Network includes stations in the United Kingdom, France and Japan—and Thompson is looking for more: "NASA encourages people with X-band antennas to contact the STEREO team. We would gladly work with them and figure out how they can join our network."

Experimenting with Piezoelectric Crystals of Rochelle Salt

Photo Credit


I'm exploring piezoelectric cyrstals, (crystals that produce a small electric potential when mechanically strained). I stumbled across a great concise history[pdf]. The outline is shown below. I also found an interesting summary of another amateur's experiments

Notes on Working with Schrodinger's Equation

I got a quick lesson on the importance of graphing my work this afternoon. After diligently calculating the expectation position of a particle as predicted by the Schrodinger equation:



I came up with the value 1/2λ.

After a little bit of thought, it occurred to me that the Schrodinger equation was symmetric about 0 and that if I was guessing the expectation, or average, value for the position of a particle predicted by the equation, I'd guess zero. So, I graphed the Schrodinger equation for the potential. Just for good measure, I went ahead and graphed the integrand of the expectation integral as well. Sure enough, the Schrodinger equation is symmetric about 0 and the areas under the expectation integrand curve to the left and right of (x=0) cancel out.

Upon checking my work I realized that I was missing a factor of x in my original integration. I multiplied the x back in and everything worked out just like the graph said it should! Not bad for taking a 20 year break between quantum mechanics study sessions. I went ahead and added the integrand for the square of x, used to calculate the standard deviation, to the graph above as well.

NOTE: Had I graphed the integrands first, I could have gotten out of doing the integral for the expectation value altogether. The areas to the left and right of 0 obviously cancel.

NOTE 2: The graphs above were created with Google Docs which is free. No pricey graphing packages required these days! No more excuses!

Have fun with it!

Compton Scattering Paper Mislabeled? It's Obvious... Not

This installment of “It’s Obvious. Not!” looks at:

Periodical: “Physical Review” Volume: 21 Page: 483, 486
Title: "A Quantum Theory of the Scattering of X-Rays by Light Elements"
Author: Arthur H. Compton

Excerpt from page 486:

In the above excerpt, Compton discusses how to calculate the momentum of an electron that caused x-ray or gamma scattering. The momentum added to the electron is the momentum of the incident photon minus the momentum of the scattered photon.

Problem: The angle of scattering, (theta), appears to be mislabeled in the above figure vs. the usage of the angle in formula 1.

In formula 1, Compton calculates the magnitude of the electron momentum as the vector difference of the momentum of the incident and scattered photons. To subtract two vectors, you place their tails together, the resulting vector that points from the head of the second to the head of the first is the difference vector as shown below and described in this Wikipedia article.

To get the magnitude of the difference vector given the magnitude of the other two vectors, you can use the Law of Cosines and the figure shown below.



And that's just what Compton does to arrive at formula 1... almost. If you read the excerpt from Compton's article carefully, you'll see that the last term of the formula for the electron's momentum magnitude is added rather than subtracted. Per normal, this unexpected change makes the derivations further along in the paper come out quite nicely. However, if you perform the magnitude calculation with the labeled value of theta, the last term has to be subtracted, rather than added, per the law of cosines.

To make everything comes out correctly, it appears that the angle that must be used is not theta, but the supplementary angle, pi minus theta. The cosine of pi minus theta is the negative of the cosine of theta which cancels Compton's sign change in the last term. Compton may have indicated this choice of angles in the text with the phrase:

Have any thoughts on this? Please let me know. I might be wrong, in which case it would be great to find out the real explanation!

Ham in a Day in Los Altos, CA

If you're interested in becoming a ham radio operator and you're going to be in the Silicon Valley area on January 24th, you should check out the

Ham Radio Training and Testing in a Day

sponsored by South County Amateur Radio Emergency Services.

It sounds like a fun event and chances are you can walk out at the end of the day with your Tech ticket!

The event will be held in Los Altos, CA which is a beautiful little city in it's own right. Bring your friends, and family. If they don't want to attend class with you, they'll love Los Altos anyway!

Getting started with PSK31

I saw a great presentation on PSK31 using the nue psk portable modem at the Mesilla Valley Radio Club this past weekend. The Nue PSK modem let's you get on the air with PSK31 without a computer. It uses an on-board micro-controller to handle the modem operations and includes an LCD for the waterfall display.

It occurred to me that my Windows Mobile enabled phone also has a programmable processor and a decent LCD display, so I went searching for PSK31 software for the Windows Mobile platform. NT7S quickly pointed me to Pocket Digi. It's a great little program that was easy to install and use! So far I've been able to decode psk31 just by placing my phone close to the speaker of an HF rig and selecting QSOs on the waterfall display.

On my Treo phone, I did have to do one quick little workaround. I first open the Windows Media Player and play any song. For some reason, this alerts the platform or the software that the speaker and microphone exist. If I don't do this, PocketDigi wakes up and complains that it can't access the microphone on the Treo.

Nobody heard me last night on transmit. On the chance that the issue is caused by my headphone speaker being used as the input to the PTT microphone, I went searching for audio-out to mic-in circuits and found this great page by G4NSJ with lots of interface circuits and info.

I'll add updates on my progress in future posts!

Have fun!
73 de KD0FNR