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| Monthly Newsletter Dedicated to the Advancement of Amateur Radio March, 2000 |
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THE PRESIDENT'S CORNER
February's meeting for MAARS turned out to be very informal due to the low attendance. Most were unable to make it due to the poor weather conditions. Thank you to Francis (WØEVJ) for his talk on transistors. For March we will meet on Friday, March 10 at 7:30 P.M. at the Red Cross Building, 2601 West Anderson, Manhattan, KS. You are welcome to attend the eating meeting at the Sirloin Stockade at 5 P.M. For the meeting Francis will finish his talk on transistors in reference to the license exams. For the business meeting we need to talk seriously about Field Day. A location needs to be decided for the event. The following people have currently signed up to help in some way or another with Field Day: Fred Stueve, KØTCS, Mike Moore, NØPVU, Kermit Fairbanks, KBØEEF, Chad Carter, NØZMG, Daryl Hasenbank, NØYHJ, and Francis Sable,WØEVJ. We also need to start thinking about when and where we want to have our Picnic. So far only one person has signed up for the Picnic committee. I'm sure Henry would appreciate some help so please sign up for it if you feel you can help. Plans for our April meeting will also be on the agenda as we hope to make this our meeting to feature a trip to Gary Johnson's lab where he generates some very impressive sparks. I'm sure most of you will be interested in this program. I will be in contact with him before our meeting to find out what our options will be for this meeting. We look forward to seeing all of you on Friday.
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SECRETARY'S MINUTES
The monthly MAARS meeting was called to order by Brian, KCØDWX, President at 7:30 P.M., Feb. 11, 2000. The meeting got underway with a lecture and demonstrations of bipolar transistor operation and theory by Francis, WØEVJ. Demonstrations were conducted with actual equipment and basic transistor circuits. This was centered on the transistor questions and answers in the ARRL license manuals as an aid to those planing to upgrade. Attendance at the meeting was lower than usual due to snow and possible hazardous road conditions. A short business session was held after the main program. There was a discussion about the return of a borrowed antenna. It was announced by Brian that the antenna has now been donated to MAARS. Meeting is adjourned.
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TECH ARTICLE: "BIPOLAR JUNCTION TRANSISTOR TEST"
How to identify the polarity and emitter, base and collector leads of a bipolar transistor and test its integrity using only an ohmmeter and one additional clip-lead and a small resistor of about 50K to 100K ohms. For test purposes, the bipolar junction transistor can be viewed as two PN junction diodes connected in series and back to back with the base lead connected to the common mid point. On the NPN transistor both the emitter and collector are connected to the N polarity end of each junction with the common P polarity ends connected to the base lead. The reverse polarities hold for the PNP transistor. The ohmmeter range selected should be a mid range like about 1K or 10K on most multimeters. Determine the voltage polarity of the ohmmeter test leads and be sure that the maximum test current is low enough so as not to damage any transistor junctions that are to be tested. On many multimeters the polarity is positive on the black lead and negative on the red lead on the ohms function. You must know the correct polarity to correctly identify the polarity of the transistor under test. A maximum current of about 10 ma or less should be safe for all or most transistors. The low ohms range on many multimeters deliver much more than 10 ma to the tested device, so avoid the lowest ohms range. Also some digital multimeters use a very low ohmmeter test voltage which will not be high enough to cause conduction through the semiconductor junctions. the older type analog meters are recommended for this test. The following is the test procedure: 1) Randomly select any two of the three leads of the transistor under test and connect the ohmmeter test leads. If the ohmmeter shows conduction this indicates that one of the two transistor leads is the base electrode. If there is no conduction, reverse the polarity to the same two transistor leads. If still no conduction this indicates that you have selected the emitter and collector leads and the remaining free transistor lead is the base electrode. Now transfer one of the two ohmmeter leads to the base lead. If you now show conduction, you now can know the polarity of the transistor (NPN or PNP). If there is conduction with the positive ohmmeter lead connected to the base lead, this is a NPN transistor. If conduction occurs with the negative ohmmeter lead connected to base lead, it is a PNP transistor. To this point the polarity of the transistor has been determined and the base lead has been identified. There remains to identify the remaining two leads as to which is emitter and collector. 2) Connect the ohmmeter test leads to the two unknown (emitter and collector) transistor leads and connect the 50K to 100K resistor to the base lead and the other end of the resistor to the positive ohmmeter lead also, if the transistor is NPN type or to the negative ohmmeter lead if the transistor is the PNP type. Notice if there is now conduction,if not, reverse the two transistor leads,with the resistor leads connected to the base and the same ohmmeter lead as previously. The polarity position which shows conduction will indicate the collector lead is the one to which the resistor is also connected. If these tests can be performed as described it indicates both junctions are good and the transistor will amplify. If the tests cannot be performed, this indicates one or both junctions are faulty. This test may not be valid for germanium transistors due to their high leakage currents.
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TREASURER'S REPORT
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If you would like to become a member of or renew your membership in the American Radio Relay League and receive the monthly issue of QST, your treasurer has a form you may use to apply. If renewing, just bring along your notice of renewal to the club meeting. The club is allowed to retain $5 of each new member's dues and $2 of each full member who is renewing. Since the club retains the dues, it is necessary for you to write your check to MAARS, and then the treasurer writes a check to ARRL for the amount minus the $5 or $2.
Dues will be due by Oct. 31 and are: regular membership $20, full-time student $10, family $30. Please complete the following when renewing your membership, even if you did so last year. Return to the Treasurer, at a meeting or to MAARS, P. O. Box 613, Manhattan, KS 66505-0613. NAME _______________________________________ CALLSIGN ____________ MAILING ADDRESS____________________________________ DATE _____________ CITY _______________________________ STATE _____ ZIP CODE _____________ TELEPHONE # (____)_______________ E-MAIL ADDRESS _______________________ FOR FAMILY MEMBERSHIP: NAME _______________________________________ CALLSIGN ____________ NAME _______________________________________ CALLSIGN ____________ CHECK THE FOLLOWING WHICH APPLY: ____ ARRL member ____ It is alright to list my e-mail address on the homepage. It is alright to list my address and telephone number for distribution only to our members. ____ How do you prefer to receive your newsletter?
____ e-mail ____ U.S. mail ____ both
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