WA6EJO
| Joined: | Fri, Feb 17th 2012, 16:31 | Roles: | N/A | Moderates: | N/A |
Latest Topics
| Topic | Created | Posts | Views | Last Activity |
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| ChatGPT - Doug DeMaw error? | Jun 20th, 15:31 | 1 | 1,501 | on 20/6/24 |
| Gain of a Quarter Wave Ground Plane Antenna? | Oct 9th 2017, 10:39 | 3 | 10,420 | on 9/8/22 |
Latest Posts
| Topic | Author | Posted On |
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| ChatGPT - Doug DeMaw error? | WA6EJO | on 20/6/24 |
| ChatGPT insists that much famed Ham Douglas DeMaw W1FB (SK) once held my callsign WA6EJO, saying his “...contributions to QST under his call sign WA6EJO are well-documented...” among other claims. I find no evidence of this. Is this true, or is it a AI brain-fart by ChatGPT? 73, Steve WA6EJO |
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| Gain of a Quarter Wave Ground Plane Antenna? | WA6EJO | on 9/8/22 |
| I finally answered my own question. Claims of -0.85 dBi to +5.31 dBi are just nuts! I decided to measure it myself using the two-identical antenna technique and the Friis equation. I made two ¼-wave ground plane antennas for 449.9 MHz. Tuned to 1.01:1 SWR. Excited with approx 5W. Received with a HP 478A/432C microwave power meter. The measurement was extremely difficult due to the reflection effects for omnidirectional antennas. If ever there was a time to use a RF anechoic chamber or two mountaintops, this was it! It took 39 gain readings to get the confidence to say that the gain of a ¼-wave ground plane is 1.32 dBi +/-0.4 dBi. To verify my technique and math I then measured the gain of the only other two identical antennas I had at hand, Two Seavey Engineering SGA-20 standard gain horns. Performed at 2.4 GHz I came within about 3% of the specified gain. 73, Steve J. Noll WA6EJO |
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| Gain of a Quarter Wave Ground Plane Antenna? | WA6EJO | on 9/10/17 |
| What is the gain of a quarter wave ground plane antenna? Simple question? Everyone has an opinion. Which one is correct? Assumption: a dipole is 2.15 dBi. -0.85 dBi “...the "1/4 wave" antenna has 0.85 dB loss as compared to an isotropic source.” A Discussion of Antenna Theory by Paul Graham (K9ERG) http://k9erg.tripod.com/theory.htm 1.15 dBi “Gain is slightly lower than a dipole (about 1 dB less)...” [2.15 - 1] US Naval Academy EE302 Lesson 13: Antenna Fundamentals, page 19. https://tinyurl.com/yd98jxo6 2.15 dBi “The performance of a quarter wave antenna (either well grounded or using a counterpoise) is essentially the same as a half-wave dipole antenna.” US Naval Academy EE302 Lesson 13: Antenna Fundamentals, page 21. https://tinyurl.com/yd98jxo6 2.15 dBi “λ/2 dipole has 2.15 dBi gain – Ground-plane gain equivalent to λ/2 dipole” Antennas 101 www.wb0hsi.org/Antennas%20101%20-%20June%202014.pdf 2.15 dBi “A monopole over an infinite ground plane is theoretically the same (identical gain, pattern, etc., in the half-space above the ground plane) as the dipole in free space.” Antenna System Guide, NIJ Guide 202-00 - NCJRS https://www.ncjrs.gov/pdffiles1/nij/185030b.pdf 2.2 dBi “The following discussion of antenna types assumes an “adequate´ ground plane is present...A single radiating element approximately 1/4 wavelength long. Directivity 2.2 dBi, 0 dBd. Antenna Basic Concepts https://www.pulseelectronics.com/antenna_basic_concepts/ 5.15 dBi “If the directivity of a dipole of length 2L has a directivity of D1 [decibels], then the directivity of a monopole antenna of length L will have a directivity of D1+3 [decibels].” [2.15 + 3] The Monopole Antenna http://www.antenna-theory.com/antennas/monopole.php 5.16 dBi “Thus, the gain of a quarter-wave monopole should have twice the gain of a corresponding half-wave dipole, or 5.16 dB.” Dipole and Monopole Antenna Gain Effective Area for Communication Formulas www.dtic.mil/get-tr-doc/pdf?AD=ADA332891 5.19 dBi “...a quarter-wave monopole, the most common type, will have a gain of 2.19 + 3 = 5.19 dBi...” Wikipedia entry for Monopole antenna. https://en.wikipedia.org/wiki/Monopole_antenna 5.31 dBi “Therefore, we deduce the antenna gain of a quarter-wave monopole antenna above virtual ground as 5.31 dB which is little bit more than twice the gain of a center-fed half-wave dipole antenna that is 2.16 dB.” Radiation Characteristics of a Quarter-Wave Monopole Antenna above Virtual Ground www.jocet.org/papers/151-L020.pdf 73, Steve J. Noll, WA6EJO |
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