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http://www.sf-arc.org/

February 2011

PO BOX 1005, NEWCASTLE, CA

February 11 OFFICERS PRESIDENT Al Martin, NI2U amartin4@wavecable.com VICE PRESIDENT Charles Baker, AE6LR ae6lr@yahoo.com SECRETARY Vacant

Club Meeting

RESOURCES

REPEATERS 145.430 (-0.6 MHz/PL 162.2) 440.575 (+5.0 MHz/PL 94.8) 223.860 (-1.6 MHz/PL 100.0) CLUB NET Thursdays, 7:30PM, W6EK/R 145.430 CLUB MEETINGS Second Friday of the month, TREASURER 7:30PM at the Library, 350 Bob Balthrope, KD6WTY Nevada St, Auburn CA kd6wty@yahoo.com CLUB BREAKFAST DIRECTORS Last Sat of the month at Mary Ann Balthorpe, KE6EST Susie’s Café, Cirby at Riverside, Gary Cunningham, KQ6RT Roseville – 8:00 AM Jim Griffith, KI6AZH NET CONTROL OPS Dave Jenkins, WB6RBE Field Day Chairman Gary Cunningham, KQ6RT Dave Hund, N6SHD Norm Medland, W6AFR Casey McPartland, W7IB REPORTERS NEWSLETTER EDITOR Satellites: Greg, KO6TH Matthew Diridoni, KC6RUO History: Gary, KQ6RT 916-749-3032 Misc Radio: Fred, K6DGW matteod@comcast.net Sunshine: Richard WA6RWS WEBMASTER: Carl A Schultz, WF6J rkuepper@ymail.com 916-482-5027

At the Key and Meeting Information Page 1 From The Presidents Shack Page 2 ARRL Testing Sessions Page 2 Miscellaneous Radio. Page 3 Fifty Years Ago at SFARC Page 4 ARRL Newsfeed Page 4

February 14

February 14-18

School Club Roundup

February 19-20

International DX Contest CW

March 5-6

International DX Contest Phone

April 17

Rookie Roundup - SSB

June 11-13

June VHF QSO Party

June 25-26

FIELD DAY!

SFARC CLUB MEETING PRESENTATION The Program for Feb meeting will be "Baluns and Ununs" and presented by Al Martin NI2U. The Tech-Ten will be on the "Repeater Auto patch and its use" presented by Richard Kuepper WA6RWS.

We encourage members to receive Sierra Signals via email to save the Club the cost of reproduction and mailing Sierra Signals is published monthly by the Sierra Foothills Amateur Radio Club for the information of it's members and friends, and is distributed via E-mail and USPS mail. Opinions expressed are those of the authors. Newsletter exchanges with other clubs via E-mail are welcomed. Contact the editor to be placed on the E-mailing list. The contents of Sierra Signals are copyrighted by the Sierra Foothills Amateur Radio Club, and all rights are reserved. That said, we will gladly permit republications for non-profit uses of all text material. Photos require the consent of all persons pictured in them, and some of our material is copyrighted by others and published by permission. You'll need to contact them for permission.


From the Presidents Shack Al Martin, NI2U President’s Thoughts SFARC has testing sessions on the first Saturday of each month at Raley's on the corner of Auburn Folsom Road & Douglas Bl. in Granite Bay. Sessions are in the multipurpose room in the back left hand corner of the store. The session starts at 8:00 AM

The SFARC has family orientated activities like the Club Picnic and the Field Days. Bob (KD6WTY) is keeping a close eye on the money and the Board will report on the funding for these events as we get there. There were a lot of favorable comments on the Picnic location last year so the plan for this year is to return there again. There is a cost involved for the facility, however. We had enough volunteers last year for our activities. As a club, I look forward to getting more people involved. So the board will be looking for new volunteers.

VISIT OUR NEW

The ARRL registration process is underway. We will make sure the SFARC Special Service Club status is continued.

WEB PAGE

See you at the meeting on February eleventh.

http://www.sf-arc.org/

CLUB BREAKFAST

Last Saturday of the month Susie’s Café, Cirby at Riverside, Roseville 8:00 AM

Sierra Foothills Amateur Radio Club

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February 2011


you’re a kid!

MISCELLANEOUS RADIO

The K9AY loop, like the Beverage, is remarkably simple, only much much smaller. The dimensions are not critical, nor is total symmetry, because, like the Beverage, it is not resonant. Gary's recommendation is about 85 ft total wire length, but do what you can.

Fred Jensen, K6DGW More Receiving Antennas Last month, we explored the realm of one receiving antenna, the Beverage, a long, low wire. While very inefficient, it has the property of being very low noise. This arises because it is very directive and receives very poorly or not at all from all directions except the direction the wire runs. Since noise arrives from all directions but the signal you wish to receive arrives from only the preferred direction, the noise will be attenuated severely. While the signal will be much weaker that it would be on an efficient antenna, the extreme loss of noise gives us a higher signal-to-noise ratio, and a pre-amplifier [found in most current transceivers] can raise the signal level if necessary.

The net signal level is proportional to the area enclosed by the wire. A taller, thinner loop will work, as will a shorter fatter one; they will just produce lower signal levels into the receiver. You hang the top from any support, anchor the two bottom sides, and tie the bottom to a ground stake. And unlike the Beverage which works best over poor grounds, the K9AY Loop doesn't care about the ground. Like the Beverage, it is terminated, and like the Beverage, that value wants to be between 350 Ω and about 550 Ω, depending on the band you are using it for. Since it's a receiving antenna, even a ¼ watt carbon composition resistor is fine.

The big downside to the Beverage is it's length. Few citybound hams have 160 meters or more [>500 ft] in which to string out wire. Even 80 meters [>250 ft] is pretty much a non-starter on a typical city lot. Fortunately, there are other antenna designs which can accomplish the same thing in much less space.

The impedance at the connection to the coax is also between 350Ω and 550Ω, so a 9:1 transformer will reduce that to around 50Ω. Since these antennas are used for the lower bands, you can use small RG-58 coax, the losses will be negligible. So, how does it work? This is not a traveling wave antenna. Instead, it exploits the fact that an electromagnetic wave has, as you might suspect from the name, both electric and magnetic components. In fact, it is impossible not to have them, as James Maxwell proved mathematically in the mid-19th century. The two components are perpendicular to each other as the wave travels forward.

K9AY Loop: Loop antennas have been around about as long as radio and they come in a variety of sizes and types. Full size loops are often used for transmitting as they are quite efficient and can produce good low angle radiation for DX. Years ago, it was common to find a piece of cardboard covering the back of a kitchen AM radio with wire wound around it in a sort of rectangular spiral. It was the antenna; my grandmother had one, and complained about the noise on her soap opera programs. I showed her how to turn the radio some on the counter and get the station clear and noise free, and from then on, she said I was as smart as Albert Einstein. ☺ Grandmothers can be soooo cool when

Imagine a wave arriving from the left in the diagram. The electric field [E] intercepts the wire and sees it as basically a vertical antenna and induces a voltage at the feed point which causes current to flow through the primary of the transformer. Verticals have an omnidirectional pattern so the current induced from the E-field doesn't depend on which direction the wave came from. The magnetic field [H] is perpendicular to E, in this example that's into and out of the page, and it sees the wire as a oneturn inductor and induces a current into the loop. This current flows through the transformer in-phase with and equal to the E-current, they add, and you hear the signal. The H-field effect is dependent on the direction of the arriving wave since it must “cut” or pass through the loop to create its current. A wave arriving from the right does exactly the same thing except the currents go through the terminating resistor and are dissipated as heat. For waves arriving from other directions, such as going into the page, the currents are not equal and are out-of-phase, and they tend to cancel. The result is a “cardioid” pattern with a very deep null off the back. Enhancements: As always seems to be the case, there are ways of complicating the design to achieve advantages. As shown, the antenna has a single direction. You can turn the directivity around by swapping the terminating resistor and transformer.

Sierra Foothills Amateur Radio Club

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February 2011


Bob Davis reported that the code class

Now, imagine a pair of these at right angles to each other [using the same top support] sort of like a Christmas tree, and some switching at the feedpoints. You could select one of four directions for receiving, get an improved signal-tonoise ratio over what you'd get from your transmitting antenna, and the whole thing fits into a 25' x 40' space. Not bad.

being held on Mon. and Thurs. at the home

of

Craig

Tindal

with

about

six

students was doing very well. The

Trivia: Maxwell's theory of electromagnetic radiation is one of the few things in physics that we can be very certain is true everywhere in the Universe, and always has been. The Universe is huge beyond comprehension, and way older than I am. Light [electromagnetic waves] from stars we see today started a long way from here [gazillions of miles] a long time ago [billions of years]. It traveled at

$5.00

merchandise

certificate

was won by Bob Davis. Motion was made to adjourn the meeting at 9:30 PM. by Frank Carmen. Fourteen were present, Visitors: K6GPB and K6VSS.

299,792,458 meters per second for all those years, and everything still conforms to Maxwell's equations when those waves arrive here at Earth. Pretty cool to have something that robust at the heart of our hobby, no?

Respectfully submitted, Sage Otow

73, Fred K6DGW

ARRL HAS AN EXCELLENT NEWS FEED If you like to have updated information from the ARRL at your fingertips, ARRL has a great Newsfeed that you can subscribe to using your internet browser.

Fifty Years Ago at SFARC Gary Cunningham, KQ6RT Feb. 8, 1961

Go to http://www.arrl.org/arrl.rss to view or even subscribe to the RSS web page and news is updated 24 hours per day.

The meeting was called to order at 8:10 P.M. by our president, Lin Hunter. The minutes of the previous meeting and the treasurer's approved.

report

were

read

Mark Your Calendar

and

Old business: discussion was

held on the coming barbecue to be held at Recreation Park. In a discussion on a meeting place it was agreed that it has to

be

a

reasonable

convenient cost.

place Some

and

club

at

a

members

expressed desire to visit and purchase ham gear in Manteca, so secretary was instructed

to

phone

to

make

sure

the

place was open. The trip will probably

June 25, 26, 2011

be made on Sun. Feb. 11th or 18th.

Sierra Foothills Amateur Radio Club

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February 2011


February 2011 Sierra Signals