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Showing posts with the label Standing wave ratio

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. 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

Simple Ham Radio Antennas: When to use antenna tuners. Post #253.

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Nowadays, the antenna transmatch ("tuner") is an integral part of many amateur radio stations.  With this device, a ham can match the output of his/her transceiver with the often unknown impedance of the antenna itself.  With a suitable balun (balanced to unbalanced) transformer, it is possible to use one antenna to cover several HF bands, especially if you're facing space restrictions on a small lot or have  to operate in "stealth" mode because of HOAs and CC&Rs.  This situation applies mostly to the use of 300 ohm tv twin lead and 450 ohm ladder line, which require a balun (1:1 or 4:1) and antenna transmatch to operate as feed lines in a multiband, single antenna system. There are times when you may not have an antenna "tuner" at your disposal, especially if you're operating in portable or emergency situations.  In my case, I remove my Drake MN-4 and MFJ 941-E transmatches from the antenna system for routine maintenance several times a