Heathkit box + more

Ray Friess rayfri at HIGHSTREAM.NET
Sun Dec 26 08:42:59 EST 2004


Stephen is right about the impedance.   And if youre running one of
those new super duper
solid state rigs, the rig may not take less kindly to it.   Glow in the
dark radios (real radios as
us old timers call them HI HI) wont even "raise an eyebrow" because the
tank circuit can handle
anywhere from about 30 ohms up to 300 and think theyre still loafing....



Stephen C. Finch wrote:

>Martin,
>
>IMO using a balun is always advisable when transmitting from a dipole.  If
>the dipole is flat, then the theoretical impedance is 72 ohms.  If the legs
>slope, the impedance will decrease with 90 to 120 degrees between the legs
>giving 50- ohms or so.  So for impedance matching, no balun would be
>necessary.
>
>However, if a coax is attached directly to a dipole, it is more common than
>not that currents will flow in the outer jacket to the coax due to the
>mismatch between the dipole and the antenna.  These currents several affect
>the antenna pattern and cause the SWR to go "haywire." This is primarily due
>to the fact that a dipole is a balanced antenna and the coax is an
>unbalanced transmission line.  Thus the balun  ("bal"anced to "un" balanced)
>will transform the balanced dipole to the unbalanced coax.
>
>There are two types of baluns - current and voltage.  I prefer the current
>baluns as they are constructed to eliminate the outer-shield currents.  Two
>good books are very insightful into this topic:  "Reflections II" by M.
>Walter Maxwell and "Building and Using Baluns and Ununs" by Jerry Sevik.
>Both are terrific additions to a ham's library.  I especially like
>Reflections II as it describes and debunks many antenna, transmissions line,
>and antenna tuner myths.
>
>Steve Finch
>AIØW
>
>-----Original Message-----
>From: Heathkit Owners and Collectors List [mailto:HEATH at LISTSERV.TEMPE.GOV]
>On Behalf Of George R. Griesbach W5GRG
>Sent: Saturday, December 25, 2004 8:01 PM
>To: HEATH at LISTSERV.TEMPE.GOV
>Subject: FS: Heathkit box + more
>
> I was rummaging around in a shop I frequent and found a large Heathkit box
>approx 24x24x12h. No Heathkit inside, but there was a complete G scale Emmit
>Kelly Circus Train set by Bachman, steam locomotive+tender+ 3 cars+ track
>and PS and misc acc.  I set it up under my tree, runs great. I will put it
>all back in the box and sell all for $150.00+ shipping from 78013.
>I also have some other Heathkit stuff on my website FS.
>pics
>http://www.comforttexas.net/gallery
>Thank You
>George R. Griesbach W5GRG
>505 River Oaks Rd.
>Comfort, Texas 78013
>w5grg at comforttexas.net
>http://www.comforttexas.net/w5grg
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