Return-Path: Received: from mx7.jersey.juno.com (mx7.jersey.juno.com [64.136.16.57]) by m22.jersey.juno.com with SMTP id AAA7R72BCAMBXYAS for (sender ); Sun, 13 May 2001 15:27:30 -0400 (EST) Received: from mx4.boston.juno.com (mx4.boston.juno.com [64.136.24.36]) by mx7.jersey.juno.com with SMTP id AAA7R72BCAGP8VPJ for (sender ); Sun, 13 May 2001 15:27:30 -0400 (EST) Received: from mail1.discovernet.net (mail1.discovernet.net [206.165.166.15]) by mx4.boston.juno.com with SMTP id AAA7R72BCADZ7AF2 for (sender ); Sun, 13 May 2001 15:27:30 -0400 (EST) Received: from tech (hi1-130-26.dialup.discovernet.net [216.221.130.26]) by mail1.discovernet.net (8.9.1/8.9.1) with SMTP id PAA30062 for ; Sun, 13 May 2001 15:34:24 -0400 Reply-To: From: "kb1dxc" To: "J_Sabini" Subject: SQUELCH BURST, June Date: Sun, 13 May 2001 15:26:33 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 June 2001 THE SQUELCH BURST a monthly publication of the STAMFORD AMATEUR RADIO ASSOCIATION President ..........Jim Murdock ............ N1NNG ........ 322-4707 Vice Pres ..........Andy Laska .............. KA1SLG ....... 531-9493 Secretary ......... Mike Cordelli ........... N1FOA ......... 838-3661 Treasurer ......... Dick Finn ..................WA1VUU ..... 323-0982 Trustee ............ Spence Heath ........... W1BWK......... 322-7539 Editors ............ Marv Fleischman ...... N1AWJ ......... 438-7889 Mike Cordelli ........... N1FOA ......... 838-3661 Dick Finn ..................WA1VUU ..... 323-0982 Y.O.J.B. Ed...... Marv Fleischman .... N1AWJ ......... 438-7889 Circ/Pub. ......... Dick Finn ................ WA1VUU ...... 323-0982 Repeaters: W1EE/R........ 146.055 in; 146.655 out (PL. 1Z, 100Hz) W1EE/R.... 442.125 in; 447.125 out (PL. 2A, 114.8Hz) Internet Home Page at http://www.qsl.net/w1ee/index_ns4.html Yearly membership $15.00 ($ 10.00 for retirees, senior members over 62, full time students, members under 16 years of age and members living over 100 miles from Stamford; $20.00 for family memberships.) This includes a copy of the club bulletin and a copy of the club roster. Send your dues, membership applications, etc. to the club Treasurer, Dick Finn, WA1VUU, 27 Ivy St., Stamford CT 06902. Non-commercial ads are printed in the SQUELCH BURST on a no charge basis, club members only. Send your ads for Ye Olde Jonque Boxxx and articles for the SQUELCH BURST to Marv Fleischman, N1AWJ, P.O. Box 113, Ridgefield, CT 06877, or e-mail to n1awj@ att.net. Meetings are held on the first Thursday of every month in the 4th floor cafeteria of the Stamford Government Center, Tresser and Washington B'lvds., Stamford, CT. Meetings start at 8:00 P.M. Minutes of the May meeting Guests - Joel and George Committee Reports - Squelch Burst - Marv, N1AWJ is putting together the May issue. If you have any stores to submit, or ask Elmer questions please send them to Marv at N1AWJ@att.net. Even if you think it's a stupid question, others may be wondering the same thing, so send it along. VE - the next session is May 12th, then the second Saturday of August, November, February and May again. We could always use more VE's, so if you haven't signed up and are interested please do so. The current testing fee is $10. Education - Current publications to study to become a HAM are available at Radio Shack, Now You're Talking is the league study guide with the full question pool in the back. There was some discussion about putting together a session for the Red Cross staff and volunteers. Public Service - Jeanine, KY1Q is taking sign ups for both the Chase Corporate Challenge late afternoon July 17th in Stamford, and the Cancer Walk in June 3rd in Stamford. The cancer walk is taking out full page color advertisements in magazines like Newsweek, so they should have an incredible turn out this year. RFI - No Report Other business - The club president Jim, N1NNG has taken ill and will be missing several meetings. Jack Alexander is also recovering from an illness, please keep both of them in your thoughts and if you hear them on the air ask how they are doing. There was discussion about the status of the repeater, we are trying to get a service monitor to get up there and work on it. Mike, N1FOA is still collecting e-mails for a group distribution list for club members. About 20% of the members have joined so far, if interested in getting the infrequent mailings please drop me a note at mike@cordelli.com . 73, Mike N1FOA ASK ELMER Elmer, I listen to the tech net on 146.85 and Dick(K2RIW) uses the term "visuar" (check spelling on this word). I would love to have an understandable explanation of this word, and how visuar relates to SWR and the output that can be expected. Signed Reflective. Dear Reflective, I have to admit that it took me a moment to recognize the “word” that you were asking about. It did give me quite a chuckle, but I have to say that the question is a very good one. The actual “word” is really a set of initials which over the years has turned into a noun by many in the Ham radio community. The term is really VSWR. The initials stand for Voltage Standing Wave Ratio. A we have some room in this issue, I will take this opportunity to turn this into a short tutorial. Maximum power transfer between a generator and its load occurs when the load's impedance equals that of the generator. You can prove this for yourself using Ohms law. Calculate the power in a resistor of 25 Ohms, 50 Ohms and 100 Ohms when driven by a generator with a voltage of 2 V and an Impedance of 50 Ohms. The circuit would be a simple series circuit with the generator in series with a 50 Ohm resistor (which simulates its impedance) and the load resistors mentioned above. First we must calculate the voltage across the load resistor for each of the above load resistors. To do this, calculate the current for each of the loads. The currents, using Ohms Law (I = E / [R load + R generator]) would be 26.6 mA, 20 mA and 13.3 mA respectively. Power = I 2 * R load. Therefore, the power into 25 Ohm load is 17.78mW, 50 Ohm load is 20 mW and 100 Ohm load is 17.78 mW. From this calculation you can easily see that the maximum power is delivered to the load of 50 Ohms. Try the calculation yourself for other generator impedance's and loads. It does work! This is known as a matched generator and load. In reality, the generator and load are not adjacent to each other. Just think of your rig and its antenna. There is a transmission line between them. In order to maintain this condition of maximum power transfer, the impedance of the transmission line should match that of the load. Energy sent down a transmission line takes a finite amount of time to reach the load. Consider a transmission line which is infinite in length. If you were to connect a generator to it, it would appear to the generator that it is connected to the impedance of the transmission line. If the line is infinite in length, the energy would be sent down the line and never get to the end. Great way to fool the generator. In reality, transmission lines are never that long. On a practical line, the energy sent down the line who's impedance is different from the load, some of the energy will be reflected back from the load. This energy would travel back to the generator, whose impedance is different then its own, and it would reflect back up the line. This energy, traveling back and forth would cause some constructive and destructive interference (read this as adding and subtracting energy) along the transmission line. The wave pattern which would be set up on the transmission line is called a Standing Wave. The reason it is called a Standing Wave is that it does not move up and down the line over time, but holds its position relative to the ends of the line. If you would like to see a standing wave, you can tie a string tightly between two nails. Then pluck the string, and watch the pattern it generates. This is a standing wave pattern. Musical instruments rely on this phenomena to produce sound. We have now established the concept of the standing wave. We have been discussing power, because power does the work. Power consists of voltage and current (P = E x I), so we can express the standing wave in terms of either of these quantities. Both power and current are troublesome to measure, so voltage wins out. In order to have a measure of the quality of the match between the generator, transmission line, and load impedance's, we will measure the magnitude of the standing wave pattern on the transmission line. As long as the length of the line is greater than 1/2 wavelength, you can use a voltage probe on the line and measure its minimum and maximum voltage (the points of constructive and destructive interference) as you travel down the line from the generator to the load. The ratio of the maximum to minimum voltage is known as the VSWR. At one time this was the only method to accurately measure the VSWR using a device called a “Slotted Line” for coaxial cable or a “Lecher Line” for a balanced system. The Slotted Line was just as the name implies, a precision coaxial transmission line with a slot cut through the shield so a probe could be inserted to measure the voltages along the line. Today we have instruments such as the “Reflectometer” which greatly simplifies the measurement of a lines VSWR. The importance of maintaining a low VSWR in a transmission line is to reduce the losses in the transmission line and assure a maximum power transfer to the load. A high VSWR can cause problems with voltage breakdown in a cable at the high voltage point. This is a fairly common occurrence when cables have been stressed due to weather or mechanical problems. It is good practice to keep the VSWR below 2:1. If this is not possible, then the cable should be chosen to withstand the high voltages and currents that will be generated due to the standing wave. This is one reason why open wire transmission line is used to feed multi-band random length dipole antennas. The open wire line can withstand the very high voltages generated due to a mismatch between the transmission line and the antenna. I hope this answers your question , probably in more detail than you wanted... but this is what happens when I have to fill up space. 73, Elmer Send your questions to “ASK ELMER” c/o Marv Fleischman, N1AWJ, PO Box 113, Ridgefield, CT 06877-0113 or e-mail to n1awj@att.net. FIELD DAY This year Field Day is being held on June 23 and 24. This is the 4th full weekend in June. SARA's will be holding the exercise outside of the Stamford Museum's Observatory. The entrance for the Field day is the rear Observatory Gate and parking lot on Scofieldtown Road. Scofieldtown Road is approx. 3/4 mile North of the Merritt Parkway. It is the road which forks left at the traffic light in front of the Museum entrance. The parking lot is about 1/4 mile up Scofieldtown road on the right. There will be a sign posted at the entrance. Come on down and join the fun! We do need your help setting up on Saturday and taring down on Sunday as well as operating the stations. PUBLIC SERVICE We need operators for the following events: Sunday, June 3 at 9AM... Cancer Walk in Stamford Tuesday, July 17 at 5:30 PM... Corporate Challange in Stamford Contact Jeanine, KY1Q at (203) 324-6865 TREASURER'S REPORT AS OF 12 MAY, 2001 INCOME EXPENSE 50/50 6.00 Postage 68.00 Dues 50.00 Phone 16.25 Int. 10.18 ______ ______ Totals $66.18 $84.25 Balances: Checkling- $1,398.83 Savings-$4,561.73 de WA1VUU YE OLDE JONQUE BOXXX Dentron GLA-1000B Linear, good cond., $350. Dentron 1KW Super Tuner, $ 90. Call Geoff, N1CAT (203) 966-7444 evenings HALLICRAFTER SX-28A RECEIVER, recapped, $275. Works good. Call Joe, N1GWO, (203) 322-4061 Evenings ESTATE SALE: ICOM IC-734 HF w/Mike, VS-20 P.S., $ 805; MFJ-16010 Antenna Tuner, $ 30. Call Jim, N1NNG, (203) 322-4707 ALUMINIUM FOLDOVER TOWER, with Rotor and Mast, suitable for roof mounting, Best Offer; 10-40M Vert. Ant., $25; Heathkit Station Monitor Mod. 614, $75. Machine Tools & Machinist's Tools for Sale, 2 South Bend 7.5 HP Go-Cart Engins. Lots of Hardware, Tools and Craft Supplies, etc. Call for Info. Call Irv, N1ATS, 348-3425 AOR 1000 XLT, 1000 Channel HH Scanner, 5KHz to 1.3 GHz continueous coverage. Exc. cond. $ 275. Call Rick, N1LYK, (203) 531-1756 YAESU FT-757 GXII, HF Rig, FP 757 HD Power Supply, FC 757 AT Tuner and MD 1B8 Desk Mike. Call George, N1HIX, (203) 357-1879 COMPLETE HF STATION, will sell all or part: Kenwood TS-820S, Remote VFO, MC-50 Mic, Dentron Linear Amp., Mosley TA-33, Ham-M Rotor, Roof Tower, MFJ Antenna Tuner, SWR Bridge, Phone Patch, etc. For details please Call Fred, K2RUR, (203) 325-2201 ICOM IC-25A 25W , 2M mobile Xcvr. w/PL, good for packet $75 obo. ICOM IC-02AT with BP-5 and BC-30 charger, Exc. Cond. $120 obo. Mac Imagewriter & Laserwriter printers, best offer. Call Jeanine, KY1Q, (203) 324-6865 APPLE PERFORMA COMPUTER....... Really Cheap Call Andy, KA1SLG, (203) 531-9493 CUSHCRAFT R5 VERT. ANTENNA: Wind Damaged and attached to my garage. Help me take it down IT'S YOURS, FREE!!! Call Frank, KA1NTG, (203) 655-7378 PARTS GALORE- Xerox 3000 Word Processor (antique) w/transformer, p/s, etc., connection to Diablo printer. FOR FREE!!! Take it away! Call Mike, KA1VWP, (203) 838-8089 ICOM IC-02AT 2M HT w BP-3, BP-5 & BP-8 Batty Packs, BC30 Charger, Spkr-Mic, Manual, $125 obo. JERROLD 900A SWEEP RF SIGNAL GENERATOR, 1MHz to 1 GHz, with detector and manual. Fully operational.. Old vacuum tube technology, 60 Lbs in table top rack cabinet. $25, obo. FatMac Computer w/ 1Meg Ram, best offer. FOR PARTS..Olevetti Accounting Machine. FREE!!!!! Take it away!!! Call Marv, N1AWJ, (203) 438-7889 Send all your ad's for YE OLDE JONQUE BOXXX to Marv Fleischman, N1AWJ, PO Box 113, Ridgefield, CT 06877. E-mail to n1awj@worldnet.att.net. Ad's must be in by the meeting night of the month prior to the publication. (December meeting for January publication) EASTERN SLOW SPEED NET Join the Eastern Slow Speed CW Net every evening on 3590 KHz at 6PM local time. CW speed is between 6 and 8 wpm. A great way to improve your CW proficiency and learn net operation. Joe, W1LUH is one of the rotating Net Control stations. THIS SPACE IS INTENTIONALLY LEFT BLANK FOR YOUR ARTICLE! Write for the SQUELCH BURST. We need your input to make this publication reflect the diverse interests and experiences of all our members.