Don, I gave you the antenna feedpoint impedances for a 2 wavelength loop and a 4 wavelength loop from L B Cebik's simulations. Those impedances are as close a one might get.
73, Don W3FPR On 1/12/2012 9:39 PM, [email protected] wrote: > 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 > ______________________________________________________________ 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
