I was a bit surprised when I installed my A3S Cushcraft that the balun is at the feed point and consists of roughly 8 turns of coax around a coffee can, taped together with black electrical tape. Not only is it easy, but it has been out in the weather for about four years & no trouble! I would duplicate that, measure the feed point at the radio, tune it if it needs it. If it seems to be way out, add some tuning at the ladder line/coax connection. I doubt a 1/4 wave stub will be practical on 80. Also, I would use enough coax to get it out of the house & then some. It is a given that the ladder line is going to radiate RF. A local guy had an 80 meter horizontal loop up on towers in the neighborhood for a while. A lightning storm came around and made a real mess of things. Last I heard, he had not made up his mind if his experience warranted replacing it. The next 80 M antenna I put up will be a loaded vertical. John Ferrell 6241 Phillippi Rd Julian NC 27283 Phone: (336)685-9606 johnferrell@earthlink.net http://DixieNC.US NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" ----- Original Message ----- From: "Thomas Sefranek" To: Sent: Thursday, January 22, 2004 4:47 PM Subject: Re: [EE]: BALUN > > -----Original Message----- > > From: pic microcontroller discussion list > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Duane > > Sent: Thursday, January 22, 2004 4:33 PM > > To: PICLIST@MITVMA.MIT.EDU > > Subject: [EE]: BALUN > > > > > > Hello everyone, > > > > Does anyone have any experience with making a BALUN to match $%) > ^^^ > 450 > > ohm Ladder > > line to 50 coax, something like RG-58? I have an 80-meter loop antenna, > > drive it with ladder line, but want to convert it to coax at the radio. > > So why do you believe you have 450 ohms at the end of the feedline > connected to your loop? (I'll bet you don't!) > > Just because you have 450 ohm feed line does NOT mean the termination > impedance IS 450 ohms. > > Simple illustration, Short the end of the feed at the loop. > Do you believe you'll have 450 ohms impedance at the radio end? > (There actually is a length of line that may make this happen, > but lets not go there, it would be a LONG line.) > > My experiences with 75 meter loops is: the feed point is ANYTHING from > a few ohms to a few HUNDRED ohms depending on where your feed point is > relative to the corner, and the height of the loop above conductive > surfaces. > > You might want to measure the impedance before you get a balun. > > BTW: I have built loops that used pulleys on the corners so I could > pull the loop feed relative to a corner to match it to 50 ohm cable! > Works GREAT on one frequency! > > > > > Thanks > > Duane > > > > -- > > http://www.piclist.com hint: PICList Posts must start with ONE topic: > > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > > > * > | __O Thomas C. Sefranek WA1RHP@ARRL.NET > |_-\<,_ Amateur Radio Operator: WA1RHP > (*)/ (*) Bicycle mobile on 145.41 MHz PL 74.4 > > ARRL Instructor, Technical Specialist, VE Contact. > http://hamradio.cmcorp.com/inventory/Inventory.html > http://www.harvardrepeater.org > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads