Part of the USA frequency spectrum use as presented by ICOM
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Part of the USA frequency spectrum use as presented by ICOM |
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As a fast riser in this new hobby of mine, I got confused where to go from here. The beautifully colored frequency table made available by ICOM made it not easier to pick a choice. Of course as an Extra Class Ham and proud of my call sign KB9TTI, I could pick any of the bottom line options of communication, but which one would be the one that would be doable with my experience? Through the contacts I made when
attending the BARC (Boulder Amateur Radio Club) meetings, I found a group of
people who were eager to help and answer my questions as they came along.
One couple stood out. Since they were retired, they could spend a lot of time
enjoying and expanding their hobby.
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Rip in his "Toy - Room" (only a small section is visible) |
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Another reliable help was Bob (W�LMA) of Freedom Avionics at Jeffco Airport Colorado. Featuring an impressive antenna farm on top of the hangar was proof of his dedication to the amateur radio cause. Meeting him frequently to bring one or the other of our ailing radios or aviation pieces for repair, I always picked up some encouragement or advice to take home. Getting stuck with interpreting my ICOM 706 manual, he got me back on the road again. Of course I had to see the IC 706 in his wife's car using a rear window mounted antenna for her VHF/UHF contacts (Mary K8AYU). Being more scholastically inclined I had to get the ARRL Antenna Book. You guessed right, the close to a 1000 pages did not make it easier to chose the antenna to build. At least I could see what not to go after, especially since I was in a time crunch and I did not want to have a half finished project before leaving again for Switzerland. I decided to start with my project at our retreat in the mountains, south of Estes Park. There were trees around the house which could serve as masts to get the antenna wires off the ground and what was most important; no restrictions in setting up anything. The easiest antenna would be a dipole I could stretch out between trees close to the house and run the feed right through the wall to my little shack I installed at my office for the 2m/70cm antenna. The following weeks I spent countless hours at the computer using the EZNEC program to find out what the various wire configurations would give and where the limitations were. One of my main concerns were the two mountains (13-14'000 ft) on either side of the N-S line. Would they shield my contacts to the East and West. Checking the Topo Maps, to my relief I found that the peaks were between 15 to 20 degrees elevation, thus not too great an obstacle for HF. |
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As I felt not yet ready to build multi wave band antennas with traps and tuning circuits I decided to try to run three wires of different length parallel all fed from the same center point. [##1] The trees however, were not far enough from the house to permit an 80m dipole. Testing various layouts I found that it did not help much to try to spread the wires in different ways to uncouple them. Running the SWR calculation I found the expected main resonance on the 40, 30, 20 meters and additional resonance on the 15m and 10m band confirmed. Adding any more dipole wires to get the 17m and 12m bands would distort the resonance of the system unnecessary and created additional resonances outside the amateur bands. |
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After having made all the calculations and planning, it was time to build the antenna and find out whether it would work. |
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| ##1 see ARRL, "Hints & Kinks", chapter 8 | |||
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Response and suggestions are appreciated to [email protected] This page was serviced last on 12. July 2008
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