Date: Sun, 8 May 94 04:30:13 PDT From: Ham-Ant Mailing List and Newsgroup Errors-To: Ham-Ant-Errors@UCSD.Edu Reply-To: Ham-Ant@UCSD.Edu Precedence: Bulk Subject: Ham-Ant Digest V94 #135 To: Ham-Ant Ham-Ant Digest Sun, 8 May 94 Volume 94 : Issue 135 Today's Topics: 2m 'Tenna for Apartment Formula for determining MFJ-1798...Another Vapor Product? NEC Archives FTP site Update Online docs for NEC2 program? Send Replies or notes for publication to: Send subscription requests to: Problems you can't solve otherwise to brian@ucsd.edu. Archives of past issues of the Ham-Ant Digest are available (by FTP only) from UCSD.Edu in directory "mailarchives/ham-ant". We trust that readers are intelligent enough to realize that all text herein consists of personal comments and does not represent the official policies or positions of any party. Your mileage may vary. So there. ---------------------------------------------------------------------- Date: 7 May 94 12:46:25 GMT From: agate!howland.reston.ans.net!pipex!demon!mailhost.interaccess.com!interaccess.com!jglazko@ucbvax.berkeley.edu Subject: 2m 'Tenna for Apartment To: ham-ant@ucsd.edu When I was in college, I had a radio set up for HF bands using some (28 ga?) magnet wire and a tuner. Did the job for what I wanted. We set it up by doing a midnight installation to the roof across the courtyard in our dorm (insulated at end), and attaching the other end at my dorm room window. Worked great for months, and it was up 4 stories. The magnet wire was almost invisible, and I didn't have any problems until it was hit by a high-flying football. The people on the ground never had any idea what they'd hit, and boy did they look surprised when the football took a sudden turn! Jack KM4RD ex-KB8EQ jglazko@interaccess.com : The Artation (CMSMANDELIN@minna.acc.iit.edu) wrote : OK, I live in an apartment. I think I can thread a coax out through my wall : mounted air conditioner and out onto my 2nd-floor balcony. : What would you recommend for a good "stealth antenna" in this situation? : (My gut feeling is to use a center-fed vertical wire dipole) ------------------------------ Date: Sat, 7 May 1994 15:19:32 GMT From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!pipex!uknet!strath-cs!cen.ex.ac.uk!jmvasnie@network.ucsd.edu Subject: Formula for determining To: ham-ant@ucsd.edu little@iamu.chi.dec.com writes: > > In article <940502215817986@chowda.com>, gary.perry@chowda.com (Gary Perry) writes: > |>GS>Is there a formula for determining the optimum distances between the > |>GS>driven element and the parasitic elements in a yagi beam? > |> > |>GS>I know the driven element should be a 1/2 wavelength and the > |>GS>reflector 5% longer and the director 5% shorter in a 3 element beam. > |>GS>How do I determine the distance between the driven element and the > |>GS>parasitic elements? What about if the yagi has more than 3 > |>GS>elements, say 7? > |> > |>Hello George, If i remember right, the spacing between elements should > |>be between .15 and .25 wavelengths at the operating frequency of the > |>antenna. The spacing you choose will also determine the front to back > |>rejection and also the gain of the antenna. As for multi element > |>antennas, the same spacing can be used. Hope this is of help to you. > > 15 to .25 wavelengths is a wide range though. Also, optimum depends upon > what you want to optimize. Grab a copy of something like yagimax or one > of the other antenna modelling programs and use that to determine what sort > of antenna you want to build. Also remember that for VHF/UHF antennas, > you'll need to consider the effect of the boom and element mounting > scheme on the length of the elements. > > In general, spacing of elements will affect the gain, pattern, and impedence > of a Yagi. So you can typically trade off one for another, but rarely can > you get something that is optimal in all. In other words, the antenna with > the highest forward gain won't necessarily have the highest front to back > ratio. It also might not have the cleanest pattern or highest resistance > to slight differences in construction technique. > > Pick up a copy of the ARRL Antenna Book for some more information on antenna > design. > > 73, > Todd > N9MWB ------------------------------ Date: 6 May 1994 21:15:47 GMT From: ihnp4.ucsd.edu!usc!nic-nac.CSU.net!charnel.ecst.csuchico.edu!psgrain!news.tek.com!tekgp4.cse.tek.com!royle@network.ucsd.edu Subject: MFJ-1798...Another Vapor Product? To: ham-ant@ucsd.edu reichrt@rtsg.mot.com (Charles H. Reichert): >Anyone out there know if this "fabulous" 80 thru 2 Meter Vertical >is for real? MFJ keeps stalling on the start of delivery dates but >keeps advertising it! Can't get any info out of them other than it >hasn't shipped yet and don't know when. MFJ was sure in a hurry to >take orders back in February but I'm starting to wonder if this wasn't >up front development money? MFJ had one at their booth at Dayton. Roy Lewallen, W7EL ------------------------------ Date: 6 May 1994 19:42:19 GMT From: koriel!male.EBay.Sun.COM!uranium!raymonda@ames.arpa Subject: NEC Archives FTP site Update To: ham-ant@ucsd.edu 5/6/94 This is an update on the latest contents of the NEC Archive FTP site located at ftp.netcom.com in /pub/rander/NEC . Note that the latest additions include: nec-pc.zip (a NEC2 executable for DOS 386/486 machines) jgraps.zip (a MS Windows utility for looking at radiation patterns calculated by NEC) There are now executables for SUN4 and IBM RS/6000 architecture workstations as well as Macintosh and 386/486 class PC's. =========================================================================== =========================================================================== NEC (Numerical Electromagnetic Code): All files with .Z prefix compressed with UNIX compress NEC Source Code and Executables: ---------------------------------- NEC2_Mac_.hqx.Z NEC2 executable for the Macintosh (in compressed .hqx format) from Barry Newberger (bsn@fusion.ph.utexas.edu) NEC2_Mac_README.txt Document file for Mac version of NEC2 nec-pc.zip NEC2 executable compiled to run on PC 386/486 Compiled with 32-bit Lahey Fortran. Requires 80x87 math coprocessor. Needs at least 2.4 MByte memory to run. from Jozef Bergervoet (bergervo@prl.phillips.nl) nec2.sun4.dl.Z SUN4 executable (dynamically linked) of NEC2 compiled for 1000 segments (Modified for interactive input/output filename specification) from Weston Beal (weston@arrakis.ebay.sun.com) nc2s1500.sun4.Z SUN4 executable (statically linked) of NEC2 compiled for 1500 segments from John Boyer (john.boyer@rd.eng.bbc.co.uk) nec2.rs6000.Z IBM RS/6000 executable of NEC2. Runs under AIX 3.2 from Doug Braun (dbraun@iil.intel.com) nec2.rs6000_readme.txt Document file for RS/6000 version of NEC2 nec81.tar.Z Fortran 77 source code for nec-81. (modified for 3000 segments) (Previously listed as nec3, but renamed to alleviate confusion with the real nec3.) (from Petri Kotilainen OH3MCK) nec81.readme.txt Readme file for nec-81 modeling program. nec2_src.tar.Z Fortran source code for NEC2 mininec3.zip BASIC source code and DOS executable for mininec3 from NOSC mininec_help.txt Help file covering the use of the Mininec antenna modeling program. Of particular use to those not having access to a copy of the Mininec manual. (contributed by Jeff Jones AB6MB, jeffj@cbnewsm.cb.att.com) NEC Utilities and Related files: ------------------------------------ nec_param_util.Z Perl script to create NEC input files from parameterized physical descriptions. from Doug Braun (dbraun@iil.intel.com) nec_post_processor.Z Creates polar plots from NEC output. MS Quick Basic source code. from John Boyer (john.boyer@rd.eng.bbc.co.uk) jgraps.zip Reads NEC output files and plots radiation patterns. Written in Visual Basic and runs under Windows 3.1 in a PC DOS environment. written by John Boyer (john.boyer@rd.eng.bbc.co.uk) necdraw.zip DOS utility for verifying correctness of NEC models. Checks adherance to rules and provides 3-D display of model. (from ACES archive) nec_hist.txt Article from the ACES newsletter outlining the history of the various versions of NEC. eam_demo.zip EAM (electromagnetic antenna modeling) demo by SAIC (Science Applications International Corp.) Runs under Windows 3.1 (DOS). EAM is a graphical user interface to NEC and BSC. Demo version has limited capability but allows visualization and inspection of small to medium size input deck and output files. (from Malcolm_Packer@cpqm.saic.com) ---------------------------------------------------------------------------- This response does not represent the official position of, or statement by, Sun Microsystems Incorporated. The above data is provided for informational purposes only. It is supplied without warranty of any kind. ---------------------------------------------------------------------------- /\ \\ \ \ \\ / / \/ / / Raymond E. Anderson / / \//\ Signal Integrity Engineer \//\ / / Sun Microsystems / / /\ / 2550 Garcia Ave. MS MIL04-16 / \\ \ Mountain View, CA 94043-1100 \ \\ \/ (408) 276-5224 (408) 956-0492 fax raymond.anderson@Sun.Com ------------------------------ Date: 7 May 94 22:07:20 GMT From: swrinde!cs.utexas.edu!convex!news.duke.edu!news-feed-1.peachnet.edu!panther.Gsu.EDU!gatech!udel!news2.sprintlink.net!news.sprintlink.net!sundog.tiac.net!usenet.elf.com!rpi!@@ihnp4.ucsd.edu Subject: Online docs for NEC2 program? To: ham-ant@ucsd.edu Are there any online docs for the NEC2 antenna program? -- Trip Martin night@acm.rpi.edu night%acm.rpi.edu@rpi.edu ------------------------------ Date: Thu, 5 May 1994 18:54:24 GMT From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!europa.eng.gtefsd.com!darwin.sura.net!hearst.acc.Virginia.EDU!cscsun!dtiller@network.ucsd.edu To: ham-ant@ucsd.edu References <2ou099$kap@taco.cc.ncsu.edu>, , t Subject : Re: 2m Amplifier mounted at antenna? Galen Watts (galen@picea.CFNR.ColoState.EDU) wrote: : In article tavernin@sun1.interlan.com (Victor Tavernini) writes: : >In article <2ou099$kap@taco.cc.ncsu.edu>, nsyslaw@riogrande.acs.ncsu.edu (Lou Williams) writes: : >|> I was curious if anyone here has tried using a 2m amplifier : >|> mounted at the antenna, instead of at the rig. : >|> in my case the feedline is over 100' : > : >If the amp has a receive preamp built-in ... then mounting it at the : >antenna would improve the noise figure of your receive system. : I've thought about this for 432, but the problem of getting 12 volts at : 10-20 amps to the top of the tower stops me. Running 120 VAC up to another : supply makes for a large tower top box with more wind load. Use a small switching supply up the tower - it'll give you more current in a smaller box. -- David Tiller | Network Administrator | Voice: (804) 752-3710 | dtiller@rmc.edu | n2kau/4 | Randolph-Macon College| Fax: (804) 752-7231 | Brady Law critique removed | P.O. Box 5005 | ICBM: 37d 42' 43.75" N | due to liberal PC pressure. | Ashland, Va 23005 | 77d 31' 32.19" W | ------------------------------ Date: 7 May 94 07:38:59 EST From: ihnp4.ucsd.edu!usc!math.ohio-state.edu!magnus.acs.ohio-state.edu!cis.ohio-state.edu!pacific.mps.ohio-state.edu!ohstpy.mps.ohio-state.edu!miavx1!miavx3.mid.muohio.edu!clmorgan@network.ucsd.edu To: ham-ant@ucsd.edu References , <2pjnao$7fe@xap.xyplex.com>, <2qadb9INN1ful@ilx018.iil.intel.com>a Subject : Re: Through-the-window on a Saturn In article <2qadb9INN1ful@ilx018.iil.intel.com>, dbraun@ilx049.iil.intel.com (Doug Braun) writes: > In article <2pjnao$7fe@xap.xyplex.com>, sas@opus.xyplex.com (Scott Sminkey - Sustaining Eng Group) writes: > |> > |> Where do people get the idea that a properly done drilled mount causes any > |> devaluation in the price of a car? > .... > |> I'll ask my usual question: can anyone cite even one single case where a > |> properly done drilled mount resulted in devaluation? > > Yes, but can anyone cite even one single case where they have > actually SOLD a car with a antenna hole in it? That's the more > relevant question. > > Doug Braun (4X/N1OWU) Yes, Doug, I can. My first "hole" was in a 1957 Chevrolet when the car was 14 months old. The next purchaser didn't bat an eye. I have learned that holes in the exterior (yes, even the roof) are easily repaired; trashing the interior, though, is more difficult (and expensive) to fix. The last three I sold have all had roof-top antennas. One went to another ham ... no problem there. The other two were plugged before delivery; however, the antenna was in place when the car was shown. Did it reduce the price of the car? I don't think so. If it had not had an antenna, I wouldn't have asked (nor expected) more from the sale. It just isn't the issue it's cracked up to be. It is, though, a personal decision, likely based on asthetics, the owner must make. 73 >< Carl K8NHE ------------------------------ End of Ham-Ant Digest V94 #135 ******************************