Foundation for Amateur Radio Scholarships

It's time to apply for the Foundation for Amateur Radio Scholarships again! Applications are due April 15th. Several of the scholarships require the recommendation of a club member, so start early. If you have questions, you can contact Dave Prestel, W8AJR, at dave.prestel@gmail.com or by phone at (410) 552-2652.

Anyone else remember self-healing GaAs transistors?

On episode 130 of SolderSmoke, N2CQR wondered why the transistors on the Venus Magellan probe were mentioned as self-healing. I remember a reference being made to self-healing GaAs transistors for use in radiation environments when I worked at a paticle accellerator during my MSEE studies, but I can't find a solid reference to this usage now. The explanation I remember went something like this:

"Radiation can damage transistors by breaking the crystalline lattice inside the semiconductor. Self-healing transistors run very hot so that when a lattice site in the semiconductor crystal is broken by radiation it is 'fixed' by the crystal effectively melting around the broken site."

Does anyone else have a solid reference to this or more information?

Thanks!

Share QSO Maps!

The QSO mapper at http://copaseticflows.appspot.com/newqso now provides sharable QSO maps! Just enter the callsigns from your QSO:

Click the Map It! button and notice the sharing toolbar:

Choose the social site you'd like to share your map on, Facebook for example, and click that button on the sharing toolbar. You'll be asked for a comment for your map link:

And a link to your map will appear on your profile like this one.
Want a link without using another site like Facebook? Click on the 'Map Link' under the sharing toolbar to go directly to your map.

Adding Google Friend Connect: Scriptaculous collision

I recently added sign-in via Google Friend Connect to the ham radio practice exams. It took a few days longer than I had planned. Using the example at: http://www.ossamples.com/api/ seemed like it should be simple enough, for an even more stripped down example try http://copaseticflows.appspot.com/glogin.
I could see that initAllData was running and sending the opensocial.newDataRequest(), but there was never a response that executed the callback function. After a few days of isolating code, it turned out that there is a conflict between Google Friend Connect and Prototype version 1.6 that ships with Scriptaculous. You can read all about it here, but the short version of the story is use the new version of Scriptaculous with Prototype 1.7.

Ham Radio Exams now have Google Sign-in

You can sign-in to save your scores and customize ham radio practice exams at copaseticflows using your Google account! Look for more ways to interact with your Google and Facebook friends coming soon. Is there anything you'd like to see? Leave a suggestion in the comments section below.

Physics Tour of New York

I came across an interesting article on the history of Physics in New York City titled, "The Physical Tourist Physics and New York City", (you can download the article for free at the preceding link. At the end of the article, the author outlines a tour through Manhattan of Physics landmarks. It sounds like fun and I hope to do it one of these days. A map of the stops on the route follows.



View Manhattan Physics Tour in a larger map

Add a mapping ham radio log book to your web page

I've written a gadget that adds a mapping ham radio log book to any web page. Just go to the gadget's customization page. copy the code from the bottom of the page and add it to your web page. You'll get a log book like the one below. It can also be added to your igoogle home page at the gadget's igoogle page.
The QSOs tab shows all the recently logged calls. Use the logger tab to enter your own QSO. Use the search tab to search for QSOs from any callsign, frequency, or mode.

Crystal Oscillator Design: Parallel and Series

On the Rockmite yahoo group today, Chuck Carpenter, W5USJ posted a very nice explanation of series vs. paralel resonant crystals along with a link to a FAQ on crystal oscillator design at:

http://www.foxonline.com/techfaqs_cry.htm#a4

Chuck' post follows:

RMers,

Here's some info sent to me by Rich at ESS.



Chuck,

The group that requested 7114 requested it in Series Resonant crystal. Most
of the other crystals that I sell are Parallel Resonant. I have included an
explanation from Fox Crystal Co. web site. They are not my supplier but the
information applies to all crystals and their manufacturers. This should
get you where you want to be.

The information that everyone needs to know is #6. 4 and 5 will help people
make a circuit oscillate where they want it.

This is from: http://www.foxonline.com/techfaqs_cry.htm#a4

More information can be found at:
http://www.oscilent.com/spec_pages/PNDescrpt/Load_Cap.htm

4. The load capacitance (CL) of my parallel resonant crystal is rated at
20pF. How do I calculate the value of the load capacitors used in my
parallel resonant oscillator circuit?

Use this formula to approximate the value of capacitors needed:

CL=((C1 x C2) / (C1 + C2)) + Cstray

Cstray is the stray capacitance in the circuit, typically 2-5pF. If the
oscillation frequency is high, the capacitor values should be increased to
lower the frequency. If the frequency is low, the capacitor values should be
decreased, thus raising the oscillation frequency. When CL =20pF, C1 and C2
will be approximately 27-33pF each, depending on the amount of stray
capacitance.

5. What is load capacitance?

Load capacitance is defined as being the total capacitance present in an
oscillator circuit as measured or calculated across the pins of the crystal
socket. Load capacitance has the effect of increasing the frequency of a
crystal unit. Please see the tutorial section for a complete explanation.

6. Will a series crystal work in a parallel circuit and vice versa?

Yes to both, but a crystal unit manufactured as a series resonant crystal
will operate at a frequency higher than expected if used in a parallel
resonant circuit. A crystal unit manufactured as a parallel resonant crystal
will operate at a frequency lower than expected if used in a series resonant
circuit.

If you need any other information then feel free to contact me,

Rich Kennedy - N4ESS
Expanded Spectrum Systems
6645 Founders St.
Zephyrhills, FL. 33542-1828
USA

813-620-0062 Office

www.expandedspectrumsystems.com

n4ess@tampabay.rr.com



Chuck Carpenter, W5USJ, Point, -|- Rains Co., TX -|- EM22cv -|- 72/73
56 years -|- 19 as K2OFN and 37as W5USJ -|- Most fun = QRP since 1984.
Website = http://www.w5usj.com