The only possible reason I can think of for using a Unun or Balun with any end-fed (Marconi) antenna is to minimize RF on the outside of the coaxial cable shield. But that seldom works because much of that RF is induced by the field around the radiator itself, not caused by RF flowing around the end of the shield at the antenna.
The only scenario that comes to mind for an antenna "springing to life" when a Unun is added is that it was set up according to the manufacturer's specs without an SWR check at the feed point and the coax is detuning it. In that case decoupling the outside of the coax might bring the system closer to resonance and provide a better match to the feedline. The only time I've considered a balun (or unun) is when I'm feeding a balanced radiator that is at least 1/2 wavelength above the ground and I particularly want to preserve its pattern. For example, the driven element in a Yagi antenna. If the antenna isn't close to at least 1/2 wavelength above the earth, its pattern is heavily influenced by the earth and structures within a few wavelengths, and a balun or unun won't correct for that. Ron AC7AC -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of David Herring Sent: Tuesday, March 08, 2011 2:30 PM To: Vernon Mauery Cc: Elecraft Mailing List Subject: Re: [Elecraft] K3 not recieving Here's a follow-on question to the reflector... Vernon's set-up brings a question to mind. He says he's using a 4:1 balun on his vertical. At first brush that seems counterintuitive, doesn't it? Isn't a vertical unbalanced? Certainly the coax is unbalanced. When you're mating an unbalanced feedline with an unbalanced antenna, wouldn't one be better off using an unun rather than a 4:1 balun? In further support of my line of questioning, I've read numerous, albeit anecdotal, reports of people being displeased with the performance of their vertical, particularly the untuned ones like Zero-Five for example. But when they add an unun they are then amazed at how the antenna allegedly "sprung to life." 73, Dave AH6TD On Mar 8, 2011, at 6:20 AM, Vernon Mauery wrote: > Yes. I can see the S-meter go from 3-4 down with static down to > nothing with quieter static. My best guess is that I am not trying > the right times at the right places. > > Thanks to everyone for the help. > > --Vernon N7OH > > On Tue, Mar 8, 2011 at 8:12 AM, Ross Primrose N4RP <n...@aiko.com> wrote: >> Does the received noise decrease when you disconnect the antenna? >> >> 73, Ross N4RP >> >> On 3/8/2011 1:06 AM, Vernon Mauery wrote: >>> At the risk of exposing what a n00b I am when it comes to HF, I really >>> need some help. I recently (last month) purchased a K3. First HF >>> radio I have owned. I got my license 2 years ago and have spent most >>> of the time since playing with VHF. I have been trying to teach >>> myself CW and decided that it was time to step into the HF waters. I >>> studied, ogled, and dreamed of my ideal HF transceiver. I finally >>> found the K3 and having looked (at least a cursory glance) at all the >>> others, I was sold. I saved my pennies and purchased. I also got >>> myself a 43' untuned vertical antenna, balun, and radial wires. >>> >>> My setup: K3/100 has 100 feet of low loss 400 coax out to the 43 foot >>> vertical on the hill in my back yard. It has 8 25 foot radials and a >>> 4:1 balun. The K3 has the KATU3, KPA3, KTCXO3-1, KFL3A-400, and >>> default 2.8KHz filters. I assembled it and did followed the >>> calibration instructions as well as I could. I think I got >>> everything, but obviously I missed something. Or maybe I just need an >>> elmer to tell me what to do. >>> >>> I cannot seem to find any signals that make the S meter go above a 3 >>> or 4. I have the RF gain turned up a fair ways (mostly to the top), >>> and I can hear static. As I tune up some of the bands on SSB, I can >>> hear a tone that changes higher in pitch as I tune up in frequency. I >>> have tried listening for CW, but I am hearing nothing as I scan >>> through the bands. I had a 10m horizontal dipole taped to my wall for >>> a while until I found time to run the coax out to the back yard. I >>> had hoped that since it was resonant on the 10m band, maybe it would >>> be able to pick up something, but it was no better (or worse) than my >>> vertical. >>> >>> As far as I can tell, the radio seems to transmit. I can see the >>> power meter moving and the SWR meter moving. The ATU seems to be able >>> to find acceptable settings on most of the bands with the vertical. >>> But I can't hear them. You can't work them if you can't hear them, >>> right? >>> >>> This is a desperate plea for help. Is it the radio or me? Please >>> have pity on the n00b and walk me through my first HF contact. >>> >>> --Vernon N7OH >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:Elecraft@mailman.qth.net >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >> >> >> -- >> FCC Section 97.313(a) "At all times, an amateur station must use the >> minimum transmitter power necessary to carry out the desired >> communications." >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> 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:Elecraft@mailman.qth.net > > 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:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
