Date and time: Tuesday, April 3, 2007 at 7:30 p.m.
Location: Salvation Army Building, 1033 Big Bethel Road.
Subject:  tbd

We have arrived at the time time of the year I love. From now through October there's a Public Service event almost every time I turn around, and the weather is usually good. They give me an excuse to put off working around the house. Check the Calandar and Public Service Events sections, charge up your batteries, grab your HT and help out.

There's some interesting infomation that's been provided. Check out the simplex contest, antenna basics and learn about NNACT. I need more articles like these from all you "Elmers" out there. If you send picture, I'll learn how to include them. Articles, stories and comments are needed along with notices for hams looking for equipment.

Feel free to share SPARKGAP with all your friends. Non-SPARK members can get on the mailing list by dropping me a note.

73,
Stu, N4STU
[Note: click on the BLUE callsign to send email to the editor]

The next edition will be mailed about April 25th.  Articles and comments due by April 22nd.

April

• Wednesdays, 7:00 pm CW Class and antenna discussion
• 2nd, Mon., 6:00 pm NNACT meeting
• 3rd, Tue., 7:30 pm SPARK meeting
• 4th, Wed., 7:30 pm PARC business meeting
• 7th, Sat., all day Daffodil Festival
• 9th - 13th, 7:15 pm HPT BoD meeting this week, day tbd
• 14th, Sat., 10:00 am PEARS meeting
• 18th, Wed., 7:30 pm PARC program meeting
• 21st, Sat., 8:00 am Simplex Exercise - see ??? below
• 28th, Sat., 8:30 am HPT breakfast meeting

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The Special Event Station at the Monitor Exhibit at The Mariners Museum was a success. Although not many contacts were made, everyone had a good time.

These are the events I am aware of that are coming, so reserve some dates to help out.
June 2nd, The Running Crab 15 K race in downtown Hampton
June 23rd and 24th, Field Day
July 14th, Medical Reserve Corp Volunteer Day
September 8th and 9th, Bay Days
October ??, Fall Festival
October ??, NN City Employees Picnic
And of course the holiday events in Newport News and Hampton.
2007 HAMPTON "HUSTLE" VHF FM SIMPLEX CONTEST

Elmer's Corner -- Observing Band Edges

There is sure to be a lot of new HF activity when the new regulations take effect on February 23.  Please remember that operators are required to keep their entire transmitted signal within the band limits.  This means that if you are operating SSB mode your signal is typically 2.8 kHz wide so a rule of thumb is to stay 3 kHz from the edge of the band.  For example if a Technician class operator wants to operate SSB on the 10 meter band then the operator should not operate any lower than 28.303 MHz or any higher than 28.497 MHz in order to stay within the band limits. 

Band edges also need to be observed when operating CW, RTTY, Data and all modes permitted in the Amateur service. 

Overdriving a SSB transmitter make your signal unreadable and it will cause splatter that can be outside of the band.  It is not just good amateur practice to produce clean transmitted signals--it's also the law, part 97.303.
reprinted from ARRL Club Newsletter dated February 23, 2007

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This is the first of two parts, submitted by Don, N4DJ
Antenna Basics Part 1

The subject of antennas is very extensive, so I will start with some fundamental concepts. We will neglect how the power is generated and delivered to the antenna.  We will first assume that a certain amount of power is delivered to a point in space and is radiated from that point equally in all directions.  Next visualize that point antenna at the center of a large ball or sphere.  At any point on the sphere we will be receiving exactly the same amount of power or signal strength.  Let us then mark off the surface of that sphere in small squares, each square 1 meter by 1 meter.  If the surface of that sphere were to contain 100 of those 1 meter by 1 meter squares, we would say that the area of the sphere were 100 square meters. Of our 100 watts radiating out from the center, we would have it dividing up such that we would end up with 1 watt for each square. The power density would be 1 watt per square meter.  (100 watts/100 square meters = 1 watt/square meter)  Note that in this case the distance from the point antenna to the surface would be 2.8 meters or about 9 feet. (Surface of a sphere = 4 x pi x (radius) squared)  As the distance increases, the power density (watts per square meter or signal strength) decreases because the surface area of the sphere rapidly increases.  Each time the distance doubles the area increases four times!  We call this the inverse square law.  It works the same way with light. 

In order to find the power density at any distance from a point source (radiating equally in all directions) we simply need divide the power at the point source (watts) by the area of a sphere (square meters) using that distance (meters) as the radius of the sphere.  This is a fairly easy calculation and because of that it leads to us using the concept of an Isotropic antenna in most antenna discussions.  An isotropic antenna is an antenna that radiates equally in all directions.  Although it is not a real antenna, it does give us a standard that we can use to compare real antennas.

A lot of times you will see comparisons made to a dipole.  If I were doing a real world antenna test, I would certainly choose to build a dipole as a reference antenna over the Isotropic which would be impossible to build!  However I would have to be sure I had the dipole oriented such that it was radiating most of its energy in the right direction for the test I was performing.  Remember that no real antenna radiates equally in ALL directions.  It turns out that the dipole, in its most favored direction, has a gain of 2.15 dB over the imaginary Isotropic antenna.  Antennas only have gain in certain directions at the expense of radiation in other directions.  The dipole has gain off the broad side at the expense of radiation off the ends. A Yagi has gain off the front at the expense of radiation off the back and sides.

Today, we have a great many antenna programs that run on computers and that makes the concept of an Isotropic antenna even more important.  I use a program called EZNEC for antenna modeling. With it I can quickly analyze an antenna find out what its feed point impedance is, and see a plot of its gain in all directions.  All gains are given as dBi (gain referenced to an Isotropic). A demo version of EZNEC can be downloaded from http://www.eznec.com  The demo version is sufficient for many simple antennas including two element Quads, four element phased verticals etc.  It is identical to the full version except for the number of wire segments being 20 vs. 500.