Hi Gang, There has been a lot of interested in my nested loop antenna array, so I wanted to bring you up to date on the latest developments. Below is a portion of the narrative I just sent to our local group: Hi Gang, Its been a whirlwind of fun Amateur Radio activity the last few days! It started early in the week when Dave, N3HCN floated the possibility of doing a casual, muti op, single transmitter effort for this weekends IARU HF contest. I thought it sounded like fun, but I warned Dave that I was concerned about my nested loop antennas, because the horizontal PVC was bowing more significantly. The array still had a good SWR and seemed to work fine, but the larger the interior of a loop, the more gain it will have, so I knew I was losing some good RF radiation in its present state. Using just 100 watts and wires to compete with folks running beams and much higher power levels, every DB of gain matters! Dave decided to come up after work on Tuesday and have a look. Our original intent was to work with what I had for this weekend, just assess the current antenna conditions and brainstorm some improvement remedies to implement before the fall contesting season, but as I lowered the antenna, one of the wooden braces, helping to keep the PVC straight, cracked! If we had any hope of working this weekends contest, we needed a solution we could implement fast! We decided to forgo the PVC structure entirely and try simply erecting the entire nested loop array with guy lines. With only one support at the top, this necessitated that we change from the square pattern I had been using and put up triangular shaped Delta Loops instead. This reduces the interior area and therefore theoretical gain from a square somewhat, but we suspected we could maintain a pretty good triangular shape with this approach, eliminating bowing and therefore increase the interior area of the square I was actually getting with my bowed installation. My existing loop was set up with 5 bands - 20, 17, 15, 12 and 10, but we also decided to just go with 3 bands, 20, 15 and 10, to increase our odds of success. With a plan in place, Dave, who wields a solder gun with infinitely more accuracy than I, took the three loops and coax home Tuesday evening to give all the connections a good clean up. Wednesday brought storms and there were other commitments for Thursday, so Friday evening was our next opportunity to fly our redesigned loops. Dave came up after work Friday evening and he, my son Brad, KB3MNE and I got right to it! I wont bore you with all the details, but there is one main trick to easily making multiple nested loops cooperate and stay aligned with only one top support and one guy at each bottom corner. First lay the entire structure out on the ground and stake the corners of all three elements! Then just tie one element to the next and when you pull it up in the air it will align beautifully! Saturday morning, we got rolling right about 8:00 AM local as the contest started. We agreed we were just going to have fun, do a casual effort and only operate for as long as we were in the mood, so it was perfectly fine when the QSO rate wasnt quite where we thought it should be to take a break from the contest, hop on line and do some Delta Loop analysis. After some research, we decided we might see improvement if we simply moved the coax connectors from the bottom center, which results in a relatively high take off angle, to one of the bottom corners, giving us a much lower take off angle, more gain towards the horizon and some additional radiated power aimed for DX. Actually, moving the connectors to the corners was relatively easy and if we had started that way to begin with all would have been fine, however, in that process, we didnt take the antennas all the way down and restake them to ensure proper relative alignment. Even with careful measuring, the nesting was now off and it took several hours before we could raise the array without one of the wire sections from one of the antennas drooping. In the end, we finally got everything hanging really nicely again. As our performance graph below shows, the effort was worth it (green is phone, blue is CW)! With the exception of 11 contacts this morning, keeping with the casual approach we wound up our effort about 9:00 PM last evening. We made 246 QSOs with 92 multipliers for a total score of 63,848. Even if we had started from scratch, we would be over half way to DXCC with 51 unique countries! Not bad for some wire and 100 watts! Here are the rest of the statistics: N3FJPs Contest Summary Report for IARU-HF Created by N3FJPs ARRL IARU HF Contest Log Total Contacts = 246 Total Points = 63,848 Operating Period: 2014/07/12 12:03 - 2014/07/13 11:58 Total Contacts by Band and Mode: Band CW Phone Dig Total % ---- -- ----- --- ----- --- 80 10 0 0 10 4 40 12 8 0 20 8 20 97 51 0 148 60 15 38 27 0 65 26 10 2 1 0 3 1 -- ----- --- ----- --- Total 159 87 0 246 100 Total Contacts by Country: Country Total % ------- ----- --- USA 80 33 Brazil 13 5 Federal Republic of Germany 10 4 Canada 7 3 European Russia 7 3 Poland 7 3 Puerto Rico 7 3 Ukraine 7 3 Finland 6 2 Italy 6 2 Spain 6 2 Czech Republic 5 2 France 5 2 Lithuania 5 2 Croatia 4 2 Slovak Republic 4 2 Asiatic Russia 3 1 Belgium 3 1 Bulgaria 3 1 Colombia 3 1 Cuba 3 1 Hungary 3 1 Latvia 3 1 Mexico 3 1 Romania 3 1 Serbia 3 1 Slovenia 3 1 Argentina 2 1 Australia 2 1 Austria 2 1 Belarus 2 1 Bosnia-Herzegovina 2 1 Curacao 2 1 Netherlands 2 1 Sweden 2 1 US Virgin Is. 2 1 Venezuela 2 1 Aland Is. 1 0 Bermuda 1 0 Bonaire 1 0 Cayman Is. 1 0 Chile 1 0 England 1 0 Estonia 1 0 Hawaii 1 0 Ireland 1 0 Luxembourg 1 0 Macedonia 1 0 Panama 1 0 Portugal 1 0 Scotland 1 0 Total = 51 Total Contacts by Continent: Continent Total % --------- ----- --- EU 111 45 NA 105 43 SA 24 10 AS 3 1 OC 3 1 Total = 5 Guys, this was a LOT of fun! Working together with Dave and Brad made it even much more enjoyable! I would love to see us do more group type activities, whether it be building antennas, working contests or sharing other aspects of our amateur radio interests! 73, Scott N3FJP
Posted on: Sun, 13 Jul 2014 16:08:40 +0000
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