Date: Fri, 29 Oct 93 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 V93 #93 To: Ham-Ant Ham-Ant Digest Fri, 29 Oct 93 Volume 93 : Issue 93 Today's Topics: Broadcast AM antenna question Butternut Butterfly Calibrating a Radio Shack SWR/POWER meter Coax termination blues. (2 msgs) Feeding and matching Yagis Nice simple HF ant 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: 28 Oct 93 19:30:03 GMT From: telenet!deceglie@uunet.uu.net Subject: Broadcast AM antenna question To: ham-ant@ucsd.edu This is not really a ham question, but here goes. I live in the Washington, DC area, and at night I sometimes can pick up a broadcast AM station out of New York (1560 kH). I really love the programming, and there is no comparable format that broadcasts locally. Oddly enough, my cheapo table radio picks it up better than my expensive stereo receiver, yet not good enough. Is there a home brew antenna solution that will enhance reception? I prefer to hook it up to the stereo receiver, which currently uses only a simple 300 ohm "T" for FM, and a helical coil for AM, that is attached to the back of the receiver. What about fading, and competing signals at the same frequency from other, more distant sources? E-mail responses please. ------------------------------ Date: Wed, 27 Oct 93 18:09:22 GMT From: tijc02!jkl141@uunet.uu.net Subject: Butternut Butterfly To: ham-ant@ucsd.edu ------------------------------ Date: Wed, 27 Oct 1993 16:46:17 GMT From: dog.ee.lbl.gov!agate!howland.reston.ans.net!spool.mu.edu!sgiblab!news.kpc.com!kpc!nat@network.ucsd.edu Subject: Calibrating a Radio Shack SWR/POWER meter To: ham-ant@ucsd.edu Hi, I am in the process of tuning a homebrew 3 element Yagi for 20m. My friend loaned me the much malaigned Radio Shack SWR/Power meter :-). Unfortunately he has misplaced the instruction booklet that came with the meter. Could someone post the instructions of calibrating the meter. The front panel has a meter 3 switches and a knob. The switches are 1. Power level 20/200/2000 2. Mode Power/Cal/SWR 3. Power Mode PEP/AVG The meter has power and swr markings on it. The SWR scale has marking starting from left at 1.0 to a red zone beyound the 3. At the end of the red zone is a red mark with "cal" on top of it. Folks can start your flamethrowers after the calibration instructions have been posted. I don't want to lose the signal in the noise :-) :-). -- ------------------------------------------------------------------------- Natarajan Gurumoorthy AB6SJ Kubota Pacific Computer, Inc. nat@kpc.com 2630 Walsh Avenue Phone 408 987 3341 Santa Clara, California 95051. ------------------------------ Date: 28 Oct 93 19:47:45 GMT From: sdd.hp.com!col.hp.com!srgenprp!alanb@hplabs.hp.com Subject: Coax termination blues. To: ham-ant@ucsd.edu ritterbus001@wcsub.ctstateu.edu (ritterbus001@wcsub.ctstateu.edu) wrote: : I have read a couple of times (notably in the ARRL Antenna Handbook) than : when preparing the ends of coax for termination, one should be very : careful _not to nick the braid or center conductor_. The articles : seemed most emphatic on this point, but did not elaborate, so it : raises some questions with me. I don't think it has anything to do with RF performance, but is simply a question of mechanical strength. If you nick the center conductor or the braid, it might break after being flexed a few times. AL N1AL ------------------------------ Date: 28 Oct 93 12:50:56 GMT From: ogicse!emory!rsiatl!ke4zv!gary@network.ucsd.edu Subject: Coax termination blues. To: ham-ant@ucsd.edu In article <1993Oct27.195442.1@wcsub.ctstateu.edu> ritterbus001@wcsub.ctstateu.edu writes: >I have read a couple of times (notably in the ARRL Antenna Handbook) than >when preparing the ends of coax for termination, one should be very >careful _not to nick the braid or center conductor_. The articles >seemed most emphatic on this point, but did not elaborate, so it >raises some questions with me. Perhaps one of you veterans of >the coax wars can shed some light on thie (Gary Coffman please read.) > >1) Why not? If I had to guess, I would guess that it had something > to do with the skin effect, but this I may be wrong (I was once :-) > How deep a cut is considered a "nick"? A couple of microns? One > quarter of the radius? It's nothing so exotic. It's just that a nick in the wire makes the wire much more prone to *breaking* at that point after being flexed a few times. How bad? If you can see the nick, or feel it with a fingernail, it's too much. >4) Those who have ever worked with coax know that theory and practice > may diverge ("In theory, theory and practice are the same. In > practice, they are not.") This begs the question, how can one > strip this nasty stuff with ordinary tools, i.e., not spending > a fortune on special strippers, etc. Buying the proper stripper and dies is the best way. Paladin is good. It's a lifetime investment. However, you can do it with an ordinary pocketknife if the knife is sharp and you have a good "touch". I used a Buck Folding Hunter that I keep *very* sharp. I can slice through jacket, braid, and inner insulation without nicking the center conductor. I then make a second cut about 1/4 inch back from the first just getting the jacket. That will make it right for working with a BNC Kings crimp connector. It shouldn't take more than 10 seconds to properly strip and terminate a coax. N fittings take a couple seconds longer because they need a third cut to bare the inner insulation for a short distance between the bare inner conductor and the exposed braid. Gary -- Gary Coffman KE4ZV |"If 10% is good enough | gatech!wa4mei!ke4zv!gary Destructive Testing Systems | for Jesus, it's good | uunet!rsiatl!ke4zv!gary 534 Shannon Way | enough for Uncle Sam."| emory!kd4nc!ke4zv!gary Lawrenceville, GA 30244 | -Ray Stevens | ------------------------------ Date: Tue, 26 Oct 1993 18:58:20 GMT From: pa.dec.com!oct17.dfe.dec.com!ryn.mro4.dec.com!est.enet.dec.com!randolph@decwrl.dec.com Subject: Feeding and matching Yagis To: ham-ant@ucsd.edu Anyone ever attempt any of the VHF Yagis in the Antenna Book? The feed is odd: the coax center conductor is tied to one leg of the driven element, then phased thru a 180 degree piece of coax to the other leg. I can't quite figure what happens to the braid. I guess this is a way of going from the unbalanced coax to a balanced feed for the Yagi...? I decided to go with a gamma match on the 2m Yagi I'm building, as it seems to work well with coax feed. I was planning a hairpin match, but I'd need some sort of balun like the above to use that. I'll probably coil the coax to choke any RF coming down the shield. This was formerly a log-periodic TV antenna, so the driven element is split. I'll have to short across it to do the gamma match. -Tom R. N1OOQ randolph@est.enet.dec.com ------------------------------ Date: Wed, 27 Oct 93 18:34:51 GMT From: dog.ee.lbl.gov!agate!howland.reston.ans.net!newsserver.jvnc.net!a3bee2.radnet.com!cyphyn!randy@network.ucsd.edu Subject: Nice simple HF ant To: ham-ant@ucsd.edu This ant will do 80 --- 10Mtrs (good enough to please me, anyway...) ====[ L tuner ]-------------------------------------------------ooo | \ 63 ft long, wire end insul. coax to \. (at tree) rig gnd sys 20 ft up All this starts at a window, where an insulator is put, to support the wire. As the house has aluminum siding, I've INCLUDED it as part of the usual gnd system (gnd rod, water pipe connects) L tuner is this ckt (home brew, but a regular PI NET tuner will work too) coax jack Adj coil and cap for least SWR for each band. SO-234 (*)---uuuuuuuuu-----+-----o to wire | 0-30uh | | adj. coil | | | | _|_/ | ___ 160 uuf variable cap ( Fair Radio Sales co.) | /| |__________________|_____o to gnd sys Coil could be a rotary inductor, but I used tap connections and a switch to select each tap 160 uuf can be as small as 100 uuf or as big as 250 uuf...BUT must be rated for 2000 volts or more so you don't flash-over. RFI is not a big thing, due to USING alum. siding as PART of my gnd sys. and so (apparantly) act as a shield. -- Randy KA1UNW If you get a shock while servicing your equipment, "Works for me!" randy@192.153.4.200 DON'T JUMP! -Peter Keyes You might break an expensive tube! ------------------------------ Date: (null) From: (null) -- -John LeRoy email: tijc02!jceng1!jkl141@uunet.uu.net phone: 1-404-509-9851 ------------------------------ End of Ham-Ant Digest V93 #93 ****************************** ******************************