Date: Thu, 12 Sep 96 08:26:33 CST From: "George T. Pasek Jr." To: qrp-l@Lehigh.EDU Subject: [4062] 40m End Fed wire Message-ID: <44334.pasek001@maroon.tc.umn.edu> Has anyone built/used a matching device to match to the high impedance seen at the feeder end of a 1/2 wave 40m wire? I'm going to be putting together a 49er and the logistics of using a longwire antenna over a dipole being less supports needed (it could be hung out a window or over the edge of a building) makes it more adaptable to my needs. I have seen the "40 meter End Fed Antenna" diagram on Frank's g3ycc@enterprise.net home page. In digging thru my junk box I found I did have some old RF/IF cans with 1/4" coil forms about 1"long that I could use to make this matching unit. How well does it work?? Any suggestions or comments about the 1/2 wave wire vs the dipole? I'm running a dipole at home which works well, but the wire seems simpler for field use. Thanks for any comments de George WD0AKZ QRP-L #610 ------------------------------ Date: Thu, 12 Sep 1996 12:14:32 -0400 From: JEVERHART@cayman.vf.mmc.com To: pasek001@maroon.tc.umn.edu Cc: qrp-l@Lehigh.EDU, jeverhart@cayman.vf.mmc.com Subject: [4073] RE: 40m End Fed wire Message-ID: <960912121432.20206956@carib.vf.mmc.com> George, Yes the end-fed half-wave can be a very practical antenna for a quick-up/quick-down portable set-up. I know that Jim Fitton - W1FMR uses that sort of setup. He uses a half-wave radiator and one or more 1/4 wave counterpoise wires. He built himself a special "tee" tuner and SWR bridge into a small die case box. He calims that it works quite well. I've done some work along those lines - I'll tell you a little, but yu'll have to wait for an upcoming article in QRP Quarterly (and QRPp?) for full details. I use a parallel resonant circuit to connect to the antenna. It is tunable so that you can tune out any reactance. The bottom side of the tuned circuit is the "cold" side and goes to at least one 1/4 wave counterpoise wire. Usint the counterpoise helps keep rf off the coaxial feedline. The low impedance connection to the coaxial feedline is via taps on the inductor. MIne uses a 0.68 " toroid and a small variable capacitor. It's probably fairly similar to the one on the G3YGG web page. It will get its baptism by fire in the upcoming QRP Afield on Sept 21. 72/73, Joe E., N2CX ------------------------------ Date: Thu, 12 Sep 1996 12:36:22 -0300 From: Greg Weinfurtner To: qrp-l@Lehigh.EDU Subject: [4074] Re: 40m End Fed wire Message-ID: MIME-version: 1.0 Content-type: text/plain; charset="us-ascii" Content-transfer-encoding: 7BIT >Has anyone built/used a matching device to match to the high impedance >seen at the feeder end of a 1/2 wave 40m wire? > >I'm going to be putting together a 49er and the logistics of using a >longwire antenna over a dipole being less supports needed (it could be >hung out a window or over the edge of a building) makes it more adaptable >to my needs. > >I have seen the "40 meter End Fed Antenna" diagram on Frank's >g3ycc@enterprise.net home page. In digging thru my junk box I found I did >have some old RF/IF cans with 1/4" coil forms about 1"long that I could >use to make this matching unit. How well does it work?? Any suggestions >or comments about the 1/2 wave wire vs the dipole? I'm running a dipole >at home which works well, but the wire seems simpler for field use. > >Thanks for any comments > George, I fed a 160 meter 1/2 wave wire with a parallel tuned tank circuit with great success. (Imagine 260' of wire in the tops of huge oak trees, thanks to my trusty bow and arrow!!) It was the antenna I used when I finally snagged Hawaii on CW with 100w! I did a lot of testing and experimenting to get it right. (Scale to your operating frequency) ______o <---- Hook 1/2 wave ant here __|_ ( | ( | _ L1 ( | /| ( __/_ ( _/__ C1 ( /| Power in --> o________( | ( | (____| | __|__ / / / Ground HINTS: 1. Make the Coil L1 out of at least #14 on a large coil form for low loss, especially necessary at QRP. 2" diameter is usually sufficient. I used 28 turns, 1/4"spacing on a 2 1/2" form. That was about 15 uh, the variable was 150pf with a 470pf capacitor in parallel with it. That made about a 470pf to 620pf capability. The capacitors should be of the transmitting variety because of the large voltages involved in a parallel circuit. 2. The L1/C1 combination should resonate at or near the operating frequency BEFORE the antenna or transmitter is hooked up. The resonant freq will probably change after ant is hooked up, that is why C1 is variable. My first antenna actually acted like an added inductor in parallel with L1, raising the resonant freq! Different antenna lengths will have various results. 3. After resonating The coil/capacitor/antenna combination via grid-dip meter, or any of your favorite methods, adjust tap for power in for lowest SWR. It is usually a few turns from the bottom of the coil. The ground doesn't need to be so great, because of the high imped end is at the feed point. There are other losses associated with this antenna but, they can be very low. I had one of the best winters on 160 that I had had in a long time with this antenna and highly recommend it. Should work great on 40! A portable set-up would be easy to assemble and very effecient for your usage! Good luck George, de **************************************************************************** * Greg Weinfurtner AEE BSS * * NN N SSSSSSS 8888888 OOOOOOO Electronic Design Splst * * N N N S 8 8 O O Ohio University Athens * * N N N SSSSSSS 8888888 O O GO BOBCATS! * * N N N S 8 8 O O * * N NN SSSSSSS 8888888 OOOOOOO * * Can thou send forth lightnings * * Amateur Radio that they may go and say unto * * DXCC WAS EM89 thee, 'Here we are'? Job 38:35 * * weinfurtner@ouvaxa.cats.ohiou.edu * * http://ouvaxa.cats.ohiou.edu/~weinfurtner * **************************************************************************** ------------------------------ Date: Thu, 12 Sep 1996 18:41:00 +0100 From: "Frank G3YCC" To: , "Low Power Amateur Radio Discussion" Subject: [4094] Re: 40m End Fed wire Message-ID: <199609122217.XAA29082@mail.enterprise.net> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit I have used the end fed as described on my web pages and yes, it does work. There was a commercial version for sale some few years ago. They worked too. You can use any container of course and a former for the coil from an old i.f can is ideal. Try a two bander maybe. Two tuned ccts in one box, with sockets for the appropriate end fed wire. Have fun! -- Frank G3YCC Ham Radio QRP Web Page: http://homepages.enterprise.net/g3ycc/ ------------------------------ Date: Thu, 12 Sep 1996 16:34:47 -0600 (MDT) From: "Thomas J. Whalen" To: Low Power Amateur Radio Discussion Subject: [4097] Half wave antenna Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Dont overlook feeding the half wave antenna with a quarter wave stub using either 300ohm twin lead or 450 ohm ladder line. One must consider the velocity facter of the line also.I've used this method for antennas from 30 meters two meters with great sucess. The great advantage is that you dont have to mess with a tuner in the field. Tom WB5QYT QRP-l #640 ------------------------------ Date: Thu, 12 Sep 1996 20:07:14 -0700 From: "Denton Bramwell" To: "'qrp-l@lehigh.edu'" Subject: [4105] RE: end fed half wave Message-ID: <01BBA0E6.21C37340@cyber-west.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable The end fed half wave is an excellent portable antenna. I have used one = many times on 40, inverted L style. =20 Most of the losses in an antenna fed against ground come from currents = circulating in lossy earth. This can be modelled as a resistor in = series with your antenna. If your ground losses amount to 66 ohms, and = your antenna's radiation resistance is 33 ohms, most of your power will = go to warming worms rather than making contacts. On the other hand, if your ground losses are 66 ohms and your feedpoint = impedance is 2,000 ohms (as in an end fed halfwave), your ground losses = will be so low that you'll never notice them. Two or three 10 or 15 foot radials flopped out on top of the ground make = an adequate ground system. It's a good idea to cut your antenna to a physical halfwave, rather than = an electrical halfwave. It will be a little bit reactive, but your = tuner will handle that, and it will require a lot less retuning as you = move frequency. There are LOTS of different ways to match it. I used a T tuner, but an = L tuner or a tapped parallel LC circuit will work equally well. The = important thing is to use a very high Q inductor, or you will have = significant tuner losses. A slug tuned RF coil is not going to work = well at all. Use a tapped air core, or good quality roller coil. Denton K7OWJ ------------------------------