Date: Wed, 8 Jun 94 04:30:18 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 #173 To: Ham-Ant Ham-Ant Digest Wed, 8 Jun 94 Volume 94 : Issue 173 Today's Topics: Antenna radiation pattern charts (2 msgs) Antenna Tuning Question bird doo on coax (3 msgs) Broadcast Band Loop Tuning (2 msgs) Curing RF Voltage on Rig case in Mob Curing RF Voltage on Rig case in Mobile Units UCSD Ham Radio archives moving Yagi antenna tuning. 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: Tue, 7 Jun 1994 08:48:51 GMT From: agate!howland.reston.ans.net!pipex!bbc!ant!boyer@ames.arpa Subject: Antenna radiation pattern charts To: ham-ant@ucsd.edu Jeff Jones (jeffj@crl.com) wrote: : I wrote a program to plot out the radiation patterns that I got from : Mininec. It works pretty well but the question I have is that while : my charts shows the gain of the antennas in DBs, I took off 3 dbs so : it isn't in DBi, I looked at the other charts in the ARRL handbook : and they all have the DBs in minus form. The best you can hope for in : theirs is 0. Could someone explain to me why that is? I see that some : are in log form and that makes sense but why the minus sign? Thanks : for any and all help for a confused ham! : -- : Jeff Jones AB6MB : jeffj@crl.com I'm not a minemec user, but a nec user. I can tell you this it's not 3dB you take off it's 2.17dB. John B john.boyer@rd.eng.bbc.co.uk ------------------------------ Date: 7 Jun 1994 21:21:03 GMT From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!europa.eng.gtefsd.com!news.umbc.edu!eff!news.kei.com!ssd.intel.com!chnews!scorpion.ch.intel.com!jbromley@network.ucsd.edu Subject: Antenna radiation pattern charts To: ham-ant@ucsd.edu In article <2svh97$bfl@crl2.crl.com>, Jeff Jones wrote: >I wrote a program to plot out the radiation patterns that I got from >Mininec. It works pretty well but the question I have is that while >my charts shows the gain of the antennas in DBs, I took off 3 dbs so >it isn't in DBi... As someone has already pointed out dBd (db referenced to a 1/2-wave dipole) is 2.17 dB less than dBi, not 3 dB. > ...I looked at the other charts in the ARRL handbook >and they all have the DBs in minus form. The best you can hope for in >theirs is 0. Could someone explain to me why that is? I see that some >are in log form and that makes sense but why the minus sign? Thanks >for any and all help for a confused ham! The usual practice is to adjust the peak of the beam for 0 dB on the chart. Note that this is purely relative, not dBd or dBi. But then you can read front-to-back ratios and sidelobe levels directly from the chart. You look at the backlobe. It peaks at -15.7 dB. So you have a 15.7 dB F/B ratio. Simple, no? >Jeff Jones AB6MB >jeffj@crl.com +-------------------------+--------------------------------------------------+ | Jim Bromley W5GYJ | | | Intel Corp. m/s C11-91 | This message transmitted with | | 5000 W. Chandler Blvd. | 100% recycled electrons. | | Chandler,AZ 85226 | | | tel: 602-554-5183 | Internet: jbromley@sedona.intel.com | +-------------------------+--------------------------------------------------+ ------------------------------ Date: Tue, 7 Jun 1994 12:47:31 GMT From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!europa.eng.gtefsd.com!darwin.sura.net!news.Vanderbilt.Edu!news@network.ucsd.edu Subject: Antenna Tuning Question To: ham-ant@ucsd.edu My question is.... will the spacing/element length vary with height above ground.... that is, if I set the element lengths and the spacing between them while on saw horses at 2' above ground using an antenna analyzer for best curves for the frequencies I want to work, will those numbers change as I put the antenna at it's working height? Or is it only impedence that changes? Bill, The height above ground will affect ALL settings you have made. Use settings you'll find in Bill Orr's yagi book and just go for it. You'll have to adjust the driven element on the tower/mast plus matching but the spacing/paracitic elements should be like the book. Don't reinvent the wheel. Good DX, K5WIM ------------------------------ Date: Tue, 7 Jun 1994 03:10:53 GMT From: ihnp4.ucsd.edu!swrinde!gatech!asuvax!pitstop.mcd.mot.com!mcdphx!schbbs!NewsWatcher!user@network.ucsd.edu Subject: bird doo on coax To: ham-ant@ucsd.edu In article <1994Jun6.114747.15159@iglou.com>, davidm@iglou.iglou.com (David Michael Moore) wrote: > sunlight eventually breaks down the jackets and eventually I will have to > replace the coax because of it. What I'd like to know is this. The local > birds have decided that my coax makes a great rest spot, and have left me > their calling cards all over the coax. Will this cause any adverse problems > with the jackets, and do I need to be cleaning this off occassionally? I doubt it David. What actually happens in deterioration with time is the outer jacket material migrates through the shield and into the dielectric. For most purposes the outer jacket serves only to protect the shield braid from physical abuse. -- Don Burns Plantation, Florida epur01@email.mot.com ------------------------------ Date: 7 Jun 94 15:59:00 GMT From: news-mail-gateway@ucsd.edu Subject: bird doo on coax To: ham-ant@ucsd.edu Dave from iglou!iglou!davidm@uunet.uu.net writes: >I have several runs of coax, mostly RG-8 and Belden 8214, that are about >10 feet above ground, running from my house out to my tower. I know that >sunlight eventually breaks down the jackets and eventually I will have to >replace the coax because of it. What I'd like to know is this. The local >birds have decided that my coax makes a great rest spot, and have left me >their calling cards all over the coax. Will this cause any adverse problems >with the jackets, and do I need to be cleaning this off occassionally? > >And yes I'm really asking this...April Fools Day was two months ago! > >David - KD4RMW >davidm@iglou.com Dave, You should have no problem with your bird doo on the coax. It may actually make that section (view inches) last longer. It would be corrosive to the connectors (acid in urine) but it won't hurt the polyethylene jacket. If you want them to stop using your coax as a resting place you might (after you clean it off) place a little mentholated petroleum jelly on the coax where they have been sitting. You might also go to a local toy store and buy a rubber snake and attach it to the coax near where they have been sitting. (Make it seem as if the snake is crawling along the coax.) If you do that be sure that the eyes are a very bright and shiny color. That works for the black birds and pigeons that we have down here. Good luck. Kevin Legal stuff: The above opinions are my own and not necessarily those of the staff, faculty, administration, or lab animals (woof!) of The University of Texas Health Science Center at San Antonio. ---------------------------------------------------------------------- Kevin R. Muenzler, WB5RUE The University of Texas Health muenzlerk@uthscsa.edu Science Center at San Antonio, Department of Computing Resources ** There is no such thing as a Monkey-Proof Program! ** ** I can prove it! ** ---------------------------------------------------------------------- ------------------------------ Date: 7 Jun 1994 17:43:49 GMT From: lll-winken.llnl.gov!noc.near.net!jericho.mc.com!fugu!levine@ames.arpa Subject: bird doo on coax To: ham-ant@ucsd.edu In article 15159@iglou.com, davidm@iglou.iglou.com (David Michael Moore) writes: -->I have several runs of coax, mostly RG-8 and Belden 8214, that are about -->10 feet above ground, running from my house out to my tower. I know that -->sunlight eventually breaks down the jackets and eventually I will have to -->replace the coax because of it. What I'd like to know is this. The local -->birds have decided that my coax makes a great rest spot, and have left me -->their calling cards all over the coax. Will this cause any adverse problems -->with the jackets, and do I need to be cleaning this off occassionally? --> -->And yes I'm really asking this...April Fools Day was two months ago! --> -->David - KD4RMW -->davidm@iglou.com --> --> Aren't you the same guy complaining about birdies on his scanner a few weeks ago also? ------------------------------ Date: Tue, 7 Jun 1994 14:24:00 GMT From: newsflash.concordia.ca!vax2.concordia.ca!hirschj@uunet.uu.net Subject: Broadcast Band Loop Tuning To: ham-ant@ucsd.edu I have the plans for a simple spiral loop antenna for the .54-1.6 MHz AM broadcast band. It shows a small variable capacitor at the base of the loop for tuning the antenna, and it says the antenna output should be fed directly to the radio and NOT through an antenna tuner unit. My radio has a built in antenna tuner. Should I then leave out the capacitor at the base of the antenna? Help please. Message-ID: <7JUN199409245061@vax2.concordia.ca> Organization: Concordia University News-Software: VAX/VMS VNEWS 1.41 ------------------------------ Date: Tue, 7 Jun 1994 20:37:02 GMT From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!swrinde!gatech!news-feed-1.peachnet.edu!darwin.sura.net!news.Vanderbilt.Edu!news@network.ucsd.edu Subject: Broadcast Band Loop Tuning To: ham-ant@ucsd.edu Jack, Keep the tuner inline with the BC antenna. I question that the simple spiral loop antenna will be as effective as a long wire (as long as you can make it). The tuner in the receiver matches the feed line/antenna to the rig. You can use all the help you can get. Good DX, K5WIM ------------------------------ Date: 7 Jun 1994 05:13:30 GMT From: ihnp4.ucsd.edu!library.ucla.edu!europa.eng.gtefsd.com!news.umbc.edu!eff!news.kei.com!news.byu.edu!news@network.ucsd.edu Subject: Curing RF Voltage on Rig case in Mob To: ham-ant@ucsd.edu Karl, Cecil, and Andy, I was delighted with your replies. I even invited my wife in to see your responses and to show her just some of what amatuer radio is all about. Your input was most helpful and instructive and I think that others besides myself benefitted therefrom. I am looking forward to implementing each of your suggestions. You guys are great and thanks again! 73, -- Vince Hadley | KA7GVQ | hadleyv@bones.et.byu.edu | ------------------------------ Date: 7 Jun 1994 15:27:35 GMT From: ihnp4.ucsd.edu!swrinde!gatech!news.byu.edu!news@network.ucsd.edu Subject: Curing RF Voltage on Rig case in Mobile Units To: ham-ant@ucsd.edu Cecil, I appreciated your comments, they help me realized I'm not going crazy but that I just need to keep trying (esp about the short case ground). Your comments about the SO239's are something I never considered before- Thanks! 73 -- Vince Hadley | KA7GVQ | hadleyv@bones.et.byu.edu | ------------------------------ Date: 7 Jun 94 23:18:29 GMT From: news-mail-gateway@ucsd.edu Subject: UCSD Ham Radio archives moving To: ham-ant@ucsd.edu The anonymous FTP archives of ham-radio-related files and programs have been moved from host UCSD.EDU to host FTP.UCSD.EDU at address 128.54.16.7. - Brian ------------------------------ Date: 7 Jun 1994 08:40:47 -0700 From: ihnp4.ucsd.edu!library.ucla.edu!psgrain!news.tek.com!cascade.ens.tek.com!not-for-mail@network.ucsd.edu Subject: Yagi antenna tuning. To: ham-ant@ucsd.edu I used to have a Wilson TA-36 tribander on a tower that tilted over. I was able to tune the antenna with it tilted over to about 2 feet off the ground on the reflector side. I found that while the tuning changed somewhat, it was predictable. As I recall the 20 meter resonant point would move up or down about 50-100 Khz. With the tilt over tower I found this an excellent arrangement and could play with the tuning of the antenna and learn alot about how it worked. This should work for any yagi antenna. Just point it skyward with the reflector 2 or 3 feet off the ground and tune it up. Then see what happens as you raise it to operating height. One thing, IT DOESN'T WORK FOR QUADs. Quads need to be adjusted at their operating height and are difficult to predict which way their tuning will shift as you raise or lower them. Terry, KI7M ------------------------------ End of Ham-Ant Digest V94 #173 ******************************