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Showing posts with the label Dipole antenna

Simple Ham Radio Antennas--40 Meter Dipole.wmv. Post #405.

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A basic, simple dipole that will get you on the air quickly. As commenters have mentioned, cut the antenna a bit longer for each element (2) to allow for trimming and SWR adjustment. If you want to use this antenna for both 40 and 15 meters without adding outrigger sections, cut the 40 meter elements for the low CW frequencies and the antenna will work on the third harmonic for the SSB portion of 15 meters. Most antenna transmatches ("tuners") will be able to handle the small mismatch in the antenna for each band. When I built one of these antennas, I cut the 40 meter portion for 7.088 Mhz (the Hawaii Afternoon net frequency). The antenna was pretty well matched at 21.264 MHz in the SSB part of the 15 meter band. Of course, you could cut the antenna for 40 meters and feed the dipole with 450 ohm ladder line into a 4:1 balun and then into your antenna tuner for coverage between 40 and 10 meters. Either way, the basic 40 meter dipole is a nice performer if you can get i

Simple Ham Radio Antennas: The 10 minute dipole. Post #313

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This is what I call a "quick and dirty" dipole antenna suitable for field expedient use or for portable operation. This video by Ten-Tec's Scott Robbins (W4PA) has received a bit of criticism, but its basic premise is excellent: "Cut, solder, and tie off." Since I'm a bit slow in the soldering department (far sightedness doesn't help much in close work...I had to use my bifocals on this project), I just took my time and built Scott's basic model in about a half-hour. I cut the antenna for the mid-point of the 40 meter band (7.150 MHz ) and used some extra RG-8X coax as the feedline. Fortunately, I had two well-placed Norfolk Pine Trees on my property and was able to get the dipole about 40 ft/12.19 meters above ground. I made a choke balun out of the last few feet of the coax nearest the antenna elements to keep stay rf off the coax shield. Without my trusty Drake MN-4 transmatch in the line, I got an initial SWR of 1.6:1. The "t

Simple Ham Radio Antennas: Building a multi-band HF Dipole Antenna. Post #312.

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Do you want an efficient multi-band HF antenna that occupies a small space and requires the minimum of construction and maintenance? Then, this video from Larry, the " Radio Ham Guy" is for you. Most of the materials will be found in your ham shack , garage storage room, or at the nearest home improvement or hardware store. This version of the popular "fan dipole" requires only one 50 ohm coaxial cable feed line, a center coax connector, a few end insulators, a tall support and a few tie off points above ground to work. Using the familiar dipole formula (468/f( MHz )=L(ft), you cut separate dipoles for each band of use, connect them to a common center connector, and "fan out" the various elements to nearby support masts, trees, or any other tall object. With careful trimming (beginning with the lowest frequency band of your choice), you can probably get a low SWR for each amateur radio band you chose. I always use an antenna transmatch (i.e. &q

Simple Ham Radio Antennas: Stealth Amateur Radio Antenna System (7 MHz to 1.3 GHz) AKA HDTV antenna. Post #302.

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Here's a curious design for a stealth antenna from Jim Whitaker . The antenna appears to be a type of Off Center Fed Dipole ( OFCD ) capable of working on 40, 20, 15, 10, 6 meters . The antenna functions as a discone for 6 meters, 2 meters, and 70 cm. I've built a few OFCD antennas , but they didn't look like Jim's. You may want to test Jim's idea if your antenna space is limited or discouraged by HOAs and CC&Rs.For the latest Amateur Radio News and Events, please check the blog sidebars. These news feeds are updated daily. Aloha es 73 de Russ (KH6JRM).

Simple Ham Radio Antennas. The Open-Wire Dipole (Doublet). Post #293

I'm still in the process of restoring my "antenna farm" after the passing of Tropical Storm Iselle on 07-08 August 2014.  I lost a few trees on my Orchidland Estates property, most of which were supporting several HF wire antennas.  I salvaged most of the wire and the 450 ohm feedline from the storm.  While I cleaned up the mess, I erected a simple multiband vertical antenna using a tall Norfolk Pine Tree as an antenna support. Next on the list is the restoration of my approximately 134-ft/40.85 meters  center-fed horizontal dipole.  The antenna is fed with 450 ohm ladder line which goes into a W9INN 4:1 balun and then via a short length of RG-8X coax into a MFJ 941E Versa Tuner II.  This feed arrangement allows multiband coverage from 3.500 MHz through 29.000 MHz. Although the antenna requires two tall supports (trees or masts), construction of the antenna is simple and the dipole doesn't require a ground radial system. Using the general formula, 468/f(

Simple Ham Radio Antennas: Antenna Basics. Post #291

One of the joys of being semi-retired, is the ability to attend a few more face-to-face meetings with your amateur radio friends.  Such was the case today, Thursday, 28 August 2014. My xyl had a substitute teaching assignment today, while I didn't.  That gave me some time to go shopping, do the laundry, take care of a few commercials for this weekend's Labor Day Drag Races (I'm the tower announcer and report back to several Hilo radio stations with race results), and meet up with a few ham friends who gather daily at the Hilo Jack In The Box Restaurant. The meetings are quite informal, with most of the discussion centered around antennas, homebrew projects, and various communications issues.  Despite having 37 years of amateur radio experience "under my belt," I always find something new and interesting at these meetings. One of the things that has always bothered me is the amount of misunderstanding surrounding antennas, both homebrewed and commercial.  It

Simple Ham Radio Antennas: An Extended Double Zepp for 20 meters. Post #277

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How would you like to have a simple dipole-like antenna that would give you almost 3dB over over the classical dipole antenna ?  You can if you're willing to build a Double Extended Zepp antenna for your favorite amateur radio band.   Now that I have enough room at my new home-in-progress in the Puna District of Hawaii Island, I decided to make a simple gain antenna for one of my favorite DX bands--20 meters. I had a spare MFJ telescoping fiberglass mast available, some leftover #14 AWG house wire in the garage, a spare 4:1 W9INN balun, a 50-ft./15.24 length of 450 ohm ladder line , a sturdy Drake MN-4 transmatch ("the tuner"), and 25-ft./7.62 meters of RG -8X coaxial cable with UHF connectors. I decided to configure the extended double zepp as an inverted V, knowing that its gain would be a bit less than a horizontal arrangement of a half wavelength dipole. With school over until mid-August, I thought this simple antenna project would give me something creat

Simple Ham Radio Antennas. A basic 40/15 meter dipole. Post #276

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My antenna "farm" at the new QTH finally is taking shape. So far, I've built and used successfully a 40-10 meter inverted V fed with ladder line , a 5/8 wavelength vertical for 20, 15, and 10 meters, a 135-ft/41.15 meters "classic doublet" fed with ladder line that works from 80-10 meters, and a 40-10 meter delta loop fed with ladder line.  I've described these antennas in past posts.  All of them work very well with relatively low power (less than 50 watts) with my older rigs (Argosy II, Swan 100 MX, Yaesu FT-7, and a Kenwood TS-520). Although I prefer multiband HF antennas fed with 450-ohm ladder line, I still use a few single or two-band antennas fed with 50-ohm coaxial cable when I wish to experiment on 40 or 15 meters.  Last Sunday, 18 May 2014, I decided to build a simple two-band dipole covering the 40 and 15 meter bands using a single piece of RG -8X coaxial cable. The dipole would be designed for the lowest frequency range and then use the thir