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I agree, altho in my case the DE jumpers ended out quite close to one another ie if 7.5 in. (quaint) out would have tuned high. On the other hand mine purchased a long time ago and there might have been changes. Do not try for front to back using signal from a station nearby as waves may arrive near vertical. Suggest setting up a qrp test oscillator with a short dipole or loop antenna 100m or so away and as high off ground as possible. Antenna works very well once tuned up. 73 end Barry Kirkwood PhD ZL1DD Signal Hill Homestay 66 Cory Road Palm Beach Waiheke Island 1240 NEW ZEALAND www.waiheke.co.nz/signal.htm ----- Original Message ----- From: Harris Leck VK4CWT <leckfam@attglobal.net> To: Paula M. Uscian <netlaw@interaccess.com>; <Force12Talk@qth.com> Sent: Monday, 27 August, 2001 9:38 PM Subject: RE: [Force 12 Talk] 40M tuning of C-4XSL > Paula, > > 1. Yes both clamps should clamp the folded wire and the jumper. This helps > to make the structure solid and to clearly identify where all the wires are > touching. I would resonant the driver first and then tune the reflector for > front to back. Note that the coil will only adjust the match, it won't > change the resonant frequency much at all. So get the low SWR point where > you want it, then adjust the coil. I also use the MFJ Analyzer and you can > zero in on the low point right on the tower if you set up the coax properly. > 2. I seem to recall Force 12 saying the leads should be around 2" but one > inch either way won't make much difference on 40. Sometimes other antennas > in the vicinity can affect the element but I would just push out the jumper > until you get the resonant point where you want it. > 3. I adjust all the jumpers on my antenna. Other wise it would be like > shortening just one side of a dipole to make it resonant. Both sides should > be the same. > > The linear loaded elements are fiddly but once you get them to the right > point everything will work fine. The difference in length between a dipole > at 6.8 Mhz and one at 7.050 Mhz is about 2.5 feet. So each side needs to be > shortened by 1.25 feet or 15" . Since you are moving the jumper on both > sides of the wire that comprises one side of the driven element, I would > change each side by about 7.5" from the original point ( you have moved one > side 2" so only move that side another 5.5"). I measure exactly where the > clamps are to make sure all four sets (8 clamps total) are in the same > place. > > GL, > > Harris VK4CWT VE6DK > > -----Original Message----- > From: Paula M. Uscian [mailto:netlaw@interaccess.com] > Sent: Monday, August 27, 2001 9:25 AM > To: Force12Talk@qth.com > Subject: [Force 12 Talk] 40M tuning of C-4XSL > > OK, we are in the final stages of tuning the 2 el 40M portion of my C-4XSL > (by the way, the 10-15-20M portion really kicks). The MFJ antenna analyzer > indicates that we are loading at around 6.800 MHz, so we are way low in the > band. The FT1000's SWR meter also indicates a high reading, but since the > resonant frequency is out of band, we cannot use the the rig to tell us > exactly where we're resonant, except by tuning it to the MFJ's output). > We've opened the 3 turn coil about as far as it will go (closing it lowers > the resonant frequency), and we've also tried moving the jumpers on the > driven element (and only on the side closest to the mast) out around 2" more > toward the element tips from the 12" presets. These action have resulted in > a noticeable but nominal impact on the resonant frequency. > > We also have looked closely at the photos in the tech note for > assembling/tuning 40M on the C-4XSL, which has led us to pose the following > questions: > > 1. When the alumoweld wire is brought through the center spreader and folded > back, should the folded back portion be held by BOTH clamps--that is, by > both the clamp that initially holds the end of the alumoweld wire to itself > AND the clamp that holds the jumper? Our thought was that by clamping in two > places, this would reduce the size of the loop formed by folding back the > alumoweld wire, and thereby possibly reduce the electrical length of the > element (since we're now clearly too long to be resonant within the 40M > band). > > If this approach is required, I assume this should be done on both the > reflector and driver? > > This is the only thing we could think of in reviewing the photos that seems > different from what we've done during assembly, and the comments to the > photos seem to suggest the same thing--clamp the folded portion of the > alumoweld with both clamps. > > 2. If the above approach is not required, does anyone have any ideas for why > we are loading so low out of band? The leads from the F12 balun are not > unusually long (around 3", an adjustment of which shouldn't make a big > difference on this band). The antenna is on a crankup that we took to full > height to make sure we are clear of interactive items like the roof. We > originally assembled the 40M elements to emphasize the CW portion of the > band, following the presets in the manual (3" away from the spreader for the > reflector, 12" away from the spreader for the driver). Should we be looking > to move the jumpers out quite a distance on both elements (even thought that > would suggest the SSB preset per the manual)? > > 3. When making tuning adjustments, do we need to adjust the jumpers at all 4 > points of connection to the alumoweld wire, or can we make the adjustments > on just the one side of the 40M driven element that is closest to reach > (these would be the points of connection that are on either side of the > boom, but on the same side of the 40M element)? I know, the manual says > adjust them all, but I thought I'd seen some suggestions here earlier that > one could make the adjustments on just one side of the element and be OK. > > Do we need to include the reflector in these adjustments, or just the driver > (again, the manual states the driver only, but want to make certain). > > Thanks. 73, Paula K9IR > > > > -------------------------------------------- > Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. > Web sites: http://www.qth.com/force12 and http://www.force12inc.com > > Submissions: send to Force12Talk@qth.com > To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com > Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk > For problems with the list, contact n4zr@qth.com > > > > -------------------------------------------- > Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. > Web sites: http://www.qth.com/force12 and http://www.force12inc.com > > Submissions: send to Force12Talk@qth.com > To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com > Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk > For problems with the list, contact n4zr@qth.com > > -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. 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