Thanks Don, I installed the SW that came with the Antenna Book.
My problem is I dont know how to model stuff so I dont have the feedpoint impedance. I am lucky someone is being kind enough to mentor me so I can learn this stuff. Cheers Don ~73 Don KD8NNU On Wed, Jan 11, 2012 at 5:30 PM, Don Wilhelm wrote: > Don, > > If you don't have TLW, you might have to invest in the ARRL Antenna > Book - it is on the CD that comes with that book. > It is "Transmission Line for Windows", and you can plug in the antenna > feedpoint impedance, the type and length of feedline and the program > tells you the impedance at the other end. > > 73, > Don W3FPR > > On 1/11/2012 5:11 PM, [email protected] wrote: >> HI Don, >> >> I wish to look into the TLW application you mention. However, I am >> not >> what it is exactly. Would you please be so kind as to point me in >> the >> proper direction. >> >> I most likely will be going back to the 1:1 balun but the promise of >> swr >> of 1.3 on 160m was nice, which I have on the 4:1. Also it is a >> current >> balun. >> >> Thanks >> >> ~73 >> Don >> KD8NNU >> >> >> On Wed, Jan 11, 2012 at 5:02 PM, Don Wilhelm wrote: >> >>> Don, >>> >>> According to L B Cebik's modeling, a 2 wavelength horizontal loop >>> will >>> have a feedpoint impedance of 180 - j125 ohms, and a 4 wavelength >>> loop >>> (the same loop used on 80 meters will have a feedpoint impedance of >>> 235 - j135. >>> Both are good candidates for the use of a 4:1 balun - but that only >>> applies if you mount the balun right at the antenna feedpoint. The >>> fact that you have 60 feet of 450 ohm feedline changes the situation >>> drastically - that is about 1/8 wavelength on 160 and close to 1/4 >>> wavelength on 80 - so the feedoint impedance at the end of that 60 >>> feet of feedline is quite a bit lower - that is most likely why your >>> 1:1 balun worked so well. You can work with L B Cebik's antenna >>> feedpoint impedances and the TLW application available from the ARRL >>> to find the feedpoint impedance at the end of the 60 foot feedline, >>> but I think you will find it closer to 50 ohms than to 200 ohms. >>> >>> The other question is what type of balun is your 4:1 balun - if it >>> is >>> a voltage type, it has no chance of stopping common mode current. >>> >>> My guess for why your current choke did not work is either that you >>> did not place it at the right point on the coax, or it was at a >>> point >>> where the RF voltage was high, and in light of a high RF voltage >>> (think impedance equal to 2000 to 4000 ohms, a choke of 5000 ohms >>> impedance does not have much of a chance to stop any current. >>> >>> So bottom line - go back to what you had before, or put the 4:1 >>> balun >>> at the antenna feedpoint where it should work if your antenna is >>> anything like L B Cebik's simulations. >>> >>> 73, >>> Don W3FPR >>> >>> On 1/11/2012 4:12 PM, [email protected] wrote: >>>> Gents, >>>> >>>> I have a ladder line and balun question that I hope someone can >>>> guide >>>> me >>>> thru. >>>> >>>> I had a good working antenna system with two antennas. First being >>>> an >>>> Alpha Delta Dipole and the second a 2WL 160m loop antenna at 40 ft >>>> in >>>> the air strung in trees. So the wire does touch the trees. >>>> >>>> Dipole is fed with coax and choked at the feed point and the loop >>>> was >>>> fed with 60 ft of ladder line to a 1:1 current balun then 25ft coax >>>> to >>>> the shack tuner. Then the amp and radio. This combination was >>>> working >>>> real well no RF problems in the shack. >>>> >>>> I was advised that I would obtain better results for better SWR at >>>> resonance and easier matching if I removed the 1:1 balun and went >>>> to >>>> a >>>> 4:1 balun. I made this change with everything else being the same. >>>> I >>>> now had RF in the shack again. >>>> >>>> I then added an isolation balun to the system by adding 6ft coax >>>> from >>>> the output of the 4:1 to a balun designs 116du which is supposed to >>>> have >>>> 4500 ohms of choking impedance on 160m and over 5000 ohms choking >>>> impedance on 80 and 40 meters. This did not eliminate the RF and >>>> I >>>> am >>>> still having problems. >>>> >>>> So here is the question, is it possible that with the combination >>>> of >>>> length of the ladder line at 60ft plus the 6 ft plus 25 ft of coax >>>> I >>>> am >>>> at a feed line length that will be a problem no matter what I do. >>>> I >>>> keep looking at the internet to try and figure this out but I am >>>> confused as some information I find says it only applies to 1:1 >>>> baluns >>>> or other factors. >>>> >>>> So anyone who can help me understand this feed line question I will >>>> be >>>> greatly appreciative. >>>> >>>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
