AAArgh Dave. Mia culpa. 66 feet is a half wave on 40, so you are good. It's on 80 that a counterpoise/ground starts to become important.
The basic point is that end fed antennas shorter than 1/2 wave become more and more dependent upon a good ground system for good efficiency. 73, Ron AC7AC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ron D'Eau Claire Sent: Tuesday, October 08, 2013 7:59 PM To: 'Esquer Dave'; [email protected] Subject: Re: [Elecraft] End fed antenna - length and SWR Hi Dave: You don't mention a ground/counterpoise. With a 66-foot radiator, that becomes important on 40 and substantially more so on 80. One 40, the impedance at the end of a 66 foot radiator is very, very high so very little current flows into the antenna. That's good because that means very little current needs to flow in to the RF ground/counterpoise -- whatever it is. The less current, the less a poor ground/counterpoise will impact the performance. The same is true on the higher bands because, even though the impedance a the end of the radiator changes, it is never anywhere near as low as it is on 40 or 80 meters. The other issue is the feed line. Presumably you have coax between the rig and the unun. The higher the SWR on the feed line, the greater the losses. The SWR at the rig end only tells a little. It's the SWR at the antenna end that matters. If it's accessible, I recommend checking it there and then consult the coaxial cable loss tables available in any Antenna handbook or on the internet to see what it is. As for the analyzer, they are nice. I've used the in commercial work, but after 60 years of stringing up wires and building beams etc., I've yet to find one important in my Hamshack. They are good for helping to figure out what's wrong when you design an antenna and the SWR is off of the chart unexpectedly. In that situation they can speed up figuring out what went wrong much faster than trial and error adjustments with an SWR bridge. Welcome to a great Hobby. You won't be a 'newbie' for long, Hi! 73, Ron AC7AC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Esquer Dave Sent: Tuesday, October 08, 2013 6:40 PM To: [email protected] Subject: [Elecraft] End fed antenna - length and SWR Hi folks, Newbie HF Dave here again with an end fed antenna design question. I have an EARCH (Emergency Amateur Radio Club, Hawaii) end fed 6-40 meter multiband HF antenna. Part of the design is the 9:1 UNUN (unbalanced to unbalanced) toroid matching transformer. I have replaced the 30' wire with 66.5 feet of 18AWG Wireman silky 532. My end fed is in a horizontal (slight slope) orientation, east-west. The antenna is about 50' above the ground (I have a 3 story house and pine trees close by). I do not have an external antenna analyzer, yet. Using the ATU in my KX-3, I have the UNTUNED SRW values below. With the KX-3 ATU, the KX-3 DOES tune all of these bands with no problem. Question: Should I do anything to improve QRP performance, shorten/lengthen the wire, or should I just go with the flow, hang loose and not worry and just enjoy my rig? REMEMBER, newbie Dave, be gentle. I've been tracking the long wire discussions on the list, there is lots of fervor. [My key = frequency/SWR] 80m 3.50/2.0 3.752.9 4.0/3.7 40m 7.0/6.9 7.15/6.9 7.3/6.9 20m 14.070/2.9 14.2/2.8 14.35/2.7 15m 21.0/2.8 21.45/3.0 10m 28.0/2.2 29.0/1.8 29.7/2.5 6m 50.0/3.0 52.0/2.3 54.0/3.7 Thanks in advance, Dave More static, more of the time . Dave Esquer, K6WDE [email protected] http://www.daveesquer.com ______________________________________________________________ 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
