A significant part of the amateur radio operators hobby is in the construction of items to be used in the hobby. The article by Dan, KB6NU, leads our discussion this week.  Dan lists sources for kits, which often serve as a starter for a first effort. 
A first kit needs not be complex. It can be a simple field strength meter which every ham needs to properly adjust antennas, or it could be a far more difficult project like a transceiver.
Many hams like to play around with antennas. The reader will find a couple of articles on antennas. One article might help understanding their behavior, the other suggest a chance to really experiment.
The information on the behavior of batteries has been taken from papers by all-battery.  They publish a weekly paper explaining the care and maintenance of various cells, alkaline, lead-acid, NICad, Lithium, lithium-ion and others. 


Did you know that batteries have a frequency dependence usage?

    There are three frequency regimes to consider when dealing with batteries:
    1. Ultra low frequencies. These are frequencies measured in inverse hours or days. In this regime the battery acts like you would expect it to. At low frequency a battery will act like a current source plus resistance. All of the energy transfer will be due to ion movement through the electrolyte and none will be due to surface charge or capacitive storage.
    2. Medium frequencies, 1kHz to 1 Hz you are dealing in the regime of ion movement. If you are trying to pull a 10 mSec pulse out of a battery you will be accessing surface charge and capacitive storage, but also charge due to charges moving across the electrolyte. By the induced charge theorem a charged particle doesn't need to move all the way across from one electrode to another to realize this energy, an ion with a charge of one unit will induce a charge on the anode of 1/10 of a unit as it moves 1/10th of the distance from the cathode to the anode. But these ions move slowly compared to the electrons in a wire, and this shows up as an increased resistance. The shorter the pulse and the higher current drawn the more the internal resistance of the cell will show itself.
    3. High frequencies for batteries are above 1kHz. In this regime impedance is a better term than resistance because capacitance and inductance come to play. Many types of batteries are spiral wound,  which introduces more inductance than flat plates would, and of course all batteries are capacitors, having parallel plates separated by a distance. If the current is drawn from the battery in a series of short pulses at high frequency strange things can happen. For example you can get crazy oscillations in a feedback situation such as a switching power supply. In these kind of applications a capacitor across the battery lets the battery move into a lower frequency regime.


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Bill Booth

Vice President
Norman "Ned" Davis

John Davidson

Elizabeth (Rene) Bush

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Lewis (Lou) Ryason

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Russ Beutler

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David Gerber

Marion Davidson

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Another month of Echolink on W8DF 224.64 repeater.  The system continues to function well with no, well almost no problems.  Echolink was brought on line last November and has operated 24 hours a day problem free since, almost.  We all have heard of some guy named Murphy.  He is real!  All I do is leave town for a week and the first day, Murphy causes a power failure.  Long distance help from family got the computer restarted and we were back on line.  I think I now have the computer set up so it will restart itself after power interruptions.
February was a rather busy month as there was 228 echolink connections. Echolink keeps a very detailed logbook which I hoped to include in Feedback, but the editor says it is much too long.  It is expected the February logbook will be available on the W8DF website.  You are encouraged to take a look at it.

Editors Note: During February there were amateurs from 15 different countries checking onto W8DF's Echolink port as well as one from every one of the ten continental call areas in the states.  Your editor called a lady in Spain and had a very nice little talk with Christina EA3FEB.  With the opportunities that this gives SMARS members, I for one, am totally lost as to why it isn't used more.

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