Date: Wed, 16 Mar 94 04:30:31 PST 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 #68 To: Ham-Ant Ham-Ant Digest Wed, 16 Mar 94 Volume 94 : Issue 68 Today's Topics: Field Day Antennas looking for comments... NOAA Antenna Advice please Subscribe test (2 msgs) Thick Ethernet as Transmission Line? (3 msgs) 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: 14 Mar 94 14:31:05 GMT From: ncrgw2.ncr.com!ncrhub2!tdbunews!nsc32!wps@uunet.uu.net Subject: Field Day Antennas To: ham-ant@ucsd.edu Last year one of the guys in our club brought a weather balloon and a long wire. The wind got too much to keep the balloon up, so the long wire, was stung from tree to lamp pole to lamp pole, etc. A tuner matched the wire from 160m through 10m. It is my understanding that the balloon will be tried again this year. We are hoping for less wind. Bill ----------------------------------------------------------------- Bill Starkgraf wps@ElSegundoCA.ncr.com AT&T Global Information Solutions (310) 524-5754 El Segundo, CA (800) 222-6245 x5754 Call: KD6UQB Simi Settlers ARC Simi Valley, CA ----------------------------------------------------------------- ------------------------------ Date: 15 Mar 1994 17:30:56 GMT From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!usc!elroy.jpl.nasa.gov!swrinde!sgiblab!cs.uoregon.edu!news.uoregon.edu!oregon.uoregon.edu!TTRENT@network.ucsd.edu Subject: looking for comments... To: ham-ant@ucsd.edu Terry Burge asked about perhaps putting up a 5/8 wave vertical for 20 mtrs., mounted with about 60 radials, only 20 or so feet long.I used a cheapo MFJ tuner at the feedpoint and got a good match across the entire 20 meter band. It would also load up well on 40 with the same settings: I still don't know why or how. This was an excellent Dx performer on 20 and 40, and was medio- cre on 80. I later moved the tuner into the shack, using heliax for a feeder, about 30 feet, and noticed little or no difference. BTW, the strong low- angle on 20 meters from the antenna caused some big-time telefone RFI, which I had to fix for a few neighbors right after the first big springtime night opening over the pole into Europe. Good luck! ------------------------------ Date: Tue, 15 Mar 1994 14:48:48 GMT From: catfish!cscsun!dtiller@uunet.uu.net Subject: NOAA Antenna Advice please To: ham-ant@ucsd.edu Herb Dieben (ag381@FreeNet.Carleton.CA) wrote: : Please comment on the following; : I have been trying to get NOAA and or Meteor data using a simple 137 Mhz : J-pole with an antenna mounted GasFet pre-amp.The feed line is about 40 feet : of RG8.Results of 24hrr/day monitoring for about 8 days has yielded nothing : at all. : If the antenna is the problem,how much better do I have to be??A computer : controlled 20 element Yagi seems a bit much to make but could be done. : Problem is that I have no assurance that that is good enough.So what should : be the next step? : Any advice would be much appreciated.Thanks in advance.Herb. Seeing as I can get NOAA and Meteor birds on my scanner with a rubber duck antenna, I'd say there's something else wrong....what freq are you trying? Some birds are turned off periodically to prevent interference or because their light angles are bad. There are regular postings about them on one on the rec.radio groups - have a look, if you've never seen one. -- David Tiller | Network Administrator | Voice: (804) 752-3710 | dtiller@rmc.edu | Randolph-Macon College| Fax: (804) 752-7231 | "Drunk, [Beowulf] slew | P.O. Box 5005 | ICBM: 37d 42' 43.75" N | no hearth companions." | Ashland, Va 23005 | 77d 31' 32.19" W | ------------------------------ Date: 16 Mar 94 05:03:49 GMT From: news-mail-gateway@ucsd.edu Subject: Subscribe To: ham-ant@ucsd.edu subscribe wish to partake in antenna forum, TNX Jim, K1ZX ------------------------------ Date: Tue, 15 Mar 1994 09:40:21 From: ihnp4.ucsd.edu!galaxy.ucr.edu!library.ucla.edu!europa.eng.gtefsd.com!darwin.sura.net!spitfire.navo.navy.mil!nrl7350.nrlssc.navy.mil!smith1@network.ucsd.edu Subject: Test To: ham-ant@ucsd.edu This is a test ------------------------------ Date: 15 Mar 1994 13:50:57 -0800 From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!apple.com!apple.com!not-for-mail@network.ucsd.edu Subject: test To: ham-ant@ucsd.edu victorc%oakhill@sps.mot.com (Victor Chen) *keeps* posting: >testing What is this? The Internet equivalent of a kerchunk? Kok Chen, AA6TY kchen@apple.com Apple Computer, Inc. ------------------------------ Date: 14 Mar 94 14:36:17 GMT From: ncrgw2.ncr.com!ncrhub2!tdbunews!nsc32!wps@uunet.uu.net Subject: Thick Ethernet as Transmission Line? To: ham-ant@ucsd.edu In article 2dd@search01.news.aol.com, nx7u@aol.com (NX7U) writes: -->only for LOW power applications. -->Probably stamped on the side of the cable somewhere is "30V MAX". These cables -->are not designed for any degree of current/voltage stress or heat dissipation. -->Other than that, they're fine! When in doubt, one coluld always call Belden. I have some thin wire Ethernet cable and did not know if it could be used with 2m and 70cm, so I called Belden (I don't have the number now - it is an 800 number) and explained what I wanted to do. They assured me it would work just fine since they use such frequencies to test their cables. Bill ----------------------------------------------------------------- Bill Starkgraf wps@ElSegundoCA.ncr.com AT&T Global Information Solutions (310) 524-5754 El Segundo, CA (800) 222-6245 x5754 Call: KD6UQB Simi Settlers ARC Simi Valley, CA ----------------------------------------------------------------- ------------------------------ Date: 15 Mar 1994 08:25:57 -0800 From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!usenet.ins.cwru.edu!eff!news.kei.com!ssd.intel.com!chnews!ornews.intel.com!ornews.intel.com!not-for-mail@network.ucsd.edu Subject: Thick Ethernet as Transmission Line? To: ham-ant@ucsd.edu In article <5Hg6ic5w165w@jackatak.raider.net> root@jackatak.raider.net (Jack GF Hill) writes: >phil@hansen.ncd.com (Phil Graham) writes: > >> 2) At about 100MHz the attenuation starts to increase. I would not recommen >> it for 2M or 70cm... Great for HF! > >*THAT* is what I said, and opined that the additional capacitance of >teh multi-layer shield coverage might be the reason... I was booed and >shoved aside. > >So, I am now curious. How did you make your measurements? What data >led you to conclude your attenuation was poor above 100 MHz? Let me jump in here and say that I've also found it to be lossy above about 100 Mhz. I don't use it for anything above 30Mhz now. I've tried both the yellow jacket stuff and some harse environment orange jacket. I don't have my Belden book here but it is 50 ohms and has no specs on VHF line loss. Since it wasn't working to my expectations on 2 meters, I removed the 100' piece and made some measurements. I used a dummy load/watt meter at the far end for the first test and the other test was made with the far end open while I checked the SWR at the driven end. The same tests with a similar length of RG-213 confirmed my suspicions that the Ethernet is lossy. I don't understand why because its got Teflon(tm) insulation, a copper coated, fat and solid center conductor, and is double shielded. Oh well. I probably shouldn't even be using it for 10 meters. While I don't remember the figures, I made the measurements when the line was fairly new and it had no Vampire taps in it. The yellow jacket has faded now. I had no trouble putting N connectors or PL-259's on it. Lately I've been using some 3/4" hardline that is surplus cable TV stuff. This is really good stuff but matching the 75 ohms is interesting and putting connectors on it is really a bitch. -- zardoz@ornews.intel.com WA7LDV ------------------------------ Date: Tue, 15 Mar 1994 20:16:38 GMT From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!vixen.cso.uiuc.edu!sdd.hp.com!hpscit.sc.hp.com!cupnews0.cup.hp.com!news1.boi.hp.com!hp-pcd!hpcvsnz!tomb@network.ucsd.edu Subject: Thick Ethernet as Transmission Line? To: ham-ant@ucsd.edu Jim Garver (zardoz@ornews.intel.com) wrote (about Thick Ethernet cable): : Let me jump in here and say that I've also found it to be lossy above about : 100 Mhz. I don't use it for anything above 30Mhz now. I've tried both the : yellow jacket stuff and some harse environment orange jacket. I don't have : my Belden book here but it is 50 ohms and has no specs on VHF line loss. : Since it wasn't working to my expectations on 2 meters, I removed the 100' : piece and made some measurements. I used a dummy load/watt meter at the : far end for the first test and the other test was made with the far end : open while I checked the SWR at the driven end. The same tests with a : similar length of RG-213 confirmed my suspicions that the Ethernet is lossy. : I don't understand why because its got Teflon(tm) insulation, a copper : coated, fat and solid center conductor, and is double shielded. Oh well. Very interesting! I have 300 feet of the foam Teflon insulated LAN cable, foil/braid/foil/braid shielded, which I measured at 2M and 440, and found to be almost exactly the attenuation I would predict from the cable geometry. It was better on both bands than RG-213/U (specs _and_ measured same way), and worse than 9913 -- which is exactly what I expected. What's going on here? Anyone else out there measured the stuff? Like Jim notes, if there is higher loss at VHF-UHF, what is the loss mechanism? Though the catalog specs (Belden) don't go above 100MHz, they do follow the expected sqrt(f) pattern that far. Could some lengths have enough local impedance variation with distance that they start acting like filters above 100MHz? 73, K7ITM ------------------------------ Date: 15 Mar 1994 21:01:26 GMT From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!cs.utexas.edu!swrinde!sdd.hp.com!hpscit.sc.hp.com!spikes@network.ucsd.edu To: ham-ant@ucsd.edu References <2lo8jt$nnj@search01.news.aol.com>, <5731@tdbunews.teradata.COM>, <1994Mar15.165720.9429@VFL.Paramax.COM>p.com Subject : Re: Field Day Antennas Pete Rossi (rossi@VFL.Paramax.COM) wrote: : Use the wind as an advantage. If your FD location has steady dependable : winds then use a kite. : Last year I operated FD from the beach were there was a nice steady 10-15 MPH : breeze all day. A 3 ft delta kite kept 33 feet of #22 wire (for 20 meters) : vertical for several hours. No problems. Worked great. I may try the : same setup with 66 feet of wire for 40 meters this year. : Pete Rossi - WA3NNA rossi@vfl.paramax.COM : ================================================================= This is a great idea if you have a steady wind. I happen to be looking at a kite catalog that has a thing called a stratoscoop. A member of the airfoil family. You are supposed to use 250 lb line! I have a small 9sqft parafoil that will really pull. This stratohoister should haul up an antenna. So, what is the breaking point for RG-8 ? :) Bill wb6rzg ------------------------------ Date: 15 Mar 1994 17:39:43 GMT From: ihnp4.ucsd.edu!pacbell.com!sgiblab!swrinde!cs.utexas.edu!howland.reston.ans.net!wupost!bigfoot.wustl.edu!cec3!jlw3@network.ucsd.edu To: ham-ant@ucsd.edu References <1994Mar12.150042.22113@ke4zv.atl.ga.us>, , <1994Mar15.145856.8336@ke4zv.atl.ga.us>wustl. Subject : Re: Grounding and lightning protection Gary Coffman (gary@ke4zv.atl.ga.us) wrote: : All I've seen are summaries, in Broadcast Engineering articles and : in Roger Block's book The Grounds for Lightning and EMP Protection. : He mentions a video tape the FAA made of the tests showing the : dissipation grids receiving repeated lightning strikes, and heavier : than normal strikes at that. : Mobile Radio Technology had a series in the April and October 1988, : and January 1989 issues about lightning prevention systems. They : tried to give both sides equal time, but it's clear that the dissipation : arrays are at best only minimally preventative, if at all. Now I have no technical expertise here, but I'd like to ask a couple of questions: 1) Does the Corona effect prevent strikes, 2) do spline balls work, 3) what about "feeler" charges? The reason I ask is that Richardson Wireless Klub (K5RWK) had a meeting last night in which a Richardson ham (I think) who works for TU Electric came and gave a ~1.5 hour lecture on lightning, prevention, and RF grounding. He brought up some of the above-mentioned issues, and also said at the end that he submitted an article to "one of the ham magazines." Your thoughts??? --jesse ------------------------------ End of Ham-Ant Digest V94 #68 ****************************** ******************************