From rfhill-l at jtan.com Tue Mar 3 01:58:58 2009 From: rfhill-l at jtan.com (rfhill-l@jtan.com) Date: Tue Mar 3 01:59:53 2009 Subject: [RFHill-L] Forth Coming Virus Message-ID: I have received several e mails from creditable sources warning of an impanding virus. Check it out, I can not personally vouch for this. The virus originates in an attachment as a POSTCARD, OR A POST CARD FROM HALLMARK. It will be from a familiar e mail account. It wipes out a critical area of the C drive. For what it's worth.... 73 Jim WA3YLQ Jim Soete 215-723-7294 Cell: 215-622-4344 wa3ylq@hotmail.com wa3ylq@arrl.net -------------- next part -------------- An HTML attachment was scrubbed... URL: http://mailman.jtan.com/pipermail/rfhill-l/attachments/20090302/f60cfa70/attachment.htm From rfhill-l at jtan.com Thu Mar 5 03:27:58 2009 From: rfhill-l at jtan.com (rfhill-l@jtan.com) Date: Thu Mar 5 03:28:54 2009 Subject: [RFHill-L] (no subject) Message-ID: <4750.96.227.219.104.1236223678.squirrel@96.227.219.104> The following is a current article from the ARRL Web Site. Off the top of my head, I got 12 correct plus the bonus. How did you do? Amateur Radio Quiz: The Yagi Antenna By H. Ward Silver, N0AX Contributing Editor n0ax@arrl.net March 02, 2009 -------------------------------------------------------------------------------- It?s a rare ham, indeed, that has not been exposed to the Yagi antenna design at one point or another in his or her ham career. Yagis are nearly everywhere -- from fantastically large wire arrays on the HF low bands to miniature metal sculptures at UHF and up. Enjoy this quiz to find out what you know about this versatile antenna! -------------------------------------------------------------------------------- 1) A parasitic element... a. is connected to the feed line. b. is not connected to the feed line. c. must be parallel to the feed line. d. is only for mechanical balance. 2) Directors are (longer) (shorter) than reflectors. 3) Directors are (longer) (shorter) than the driven element. 4) Second directors are (longer) (shorter) than the first directors. 5) A Yagi's driven element generally has a feedpoint impedance (lower) (higher) than 50 ohms. 6) Which of following is NOT a useful transmission-line impedance matching design to transform the Yagi driven-element impedance to 50 ohms for coax feed? a. Strip-line b. Gamma match c. Beta match d. Hairpin 7) "Plumber's Delight" construction means that all elements are... a. made from threaded pipe. b. not insulated from the boom. c. at the same RF potential. d. trapped. 8) A "driven cell" refers to... a. a loop used as the driven element. b. two or more driven elements. c. more than one Yagi on a single mast. d. extra-strong rotator hardware. 9) Reflectors have self-resonant frequencies (higher) (lower) than that of the driven element. 10) Adding parasitic elements is done to improve the antenna's... a. front-to-back ratio. b. forward gain. c. both (a) and (b) d. neither 11) The Yagi antenna was first described in... a. 1926-28. b. 1936. c. 1946. d. 1962. 12) The "2:1 Bandwidth" of a Yagi refers to the frequency range over which the antenna maintains a... a. 2-to-1 SWR or less. b. front-to-back ratio of at least 3 dB. c. forward gain of at least 3 dB. d. efficiency of 90 percent or greater. 13) A "quagi" is... a. an array of four Yagis. b. a Yagi with one or more quad-loop elements. c. a quasi-Yagi design. d. a lightweight Yagi. 14) "Tapered elements" are... a. spaced closer together at one end of the antenna. b. covered with insulating tape. c. smaller in diameter at their tips than in their centers. d. no longer in general use. 15) Increasing the number of elements in a Yagi (increases) (decreases) the antenna pattern beamwidth. Bonus Question: Who was Dr Yagi's co-inventor of the antenna that is now only known by Yagi's name?