Log-Periodic Dipole Array or LPDA

skylarkcolo
Jun 18, 2024
7 min read

Updated: 3 days ago

A view of one of the Large HF LPDA Log Beam antennas test tested and surveyed at General Steven Walz 1200 acre world largest antenna site and test range, k0uo ham radio station k0uo,
miles of antennas for ham radio
dozens of tall antenna support structures, like FCC registered towers up to 195 foot, numerous 100 foot wood power-line poles, concrete silos, and portable mobile tower view from the top of the FCC TOWER NUMBER AR #1216715 on the k0uo antenna test and rhombic farm is a big gun and contester dream station, the biggest ham station with the highest gain antennas in the world also using Log LPDA Arrays on a 100 foot tower and one on a 195 foot tower — Log LPDA Antenna being tested, T6 **Tennadyne which is on a 12 foot boom**

This is a purposefully designed antenna, not a compromised one, which was part of a United States Air Force "Secret" project in the early 1950s. It provides more gain than Hex-beams and most Triband Yagi beams. Then in 1957, R.H. DuHamel and D.E. Isbell of the University of Illinois published the first work on what was to become known as the log periodic dipole array. The impedance of the Log-periodic antenna is a logarithmically periodic function of frequency. The main advantage of an LPDA is its consistent characteristics over a wide frequency range, offering very broad bandwidths without moving parts, fiberglass, traps, or wires that can break, and it is directional. It delivers more gain than a Hexbeam or a small Tri-band Yagi. This is why many services and agencies rely on LPDA antennas for maintaining reliable long-distance communication links for embassies, energy companies, high-frequency stock trading groups, the FBI, FAA, ship-to-shore communications, MARS, emergency operations centers, FEMA, and armed forces worldwide. The Log can handle very high RF power, and many commercial short-wave broadcast radio stations use Logs with up to 500,000 watts. A Log is an excellent replacement for the no longer produced SteppIR antenna.

The above photo shows one of my LPDA's, yagi-style log being tested (no tuning is ever required).

Diagram of LPDA made of wire I have built a number of wire log arrays over the years at the K0UO world biggest antenna farm — **A Fixed HF Log-Periodic Dipole Array or LPDA**

Understanding the Log-Periodic Antenna Design

The Log-periodic antenna is a fascinating and sophisticated design that employs half-wave dipoles for its construction. In this configuration, every element of the antenna is actively driven, meaning that each dipole contributes to the overall performance of the antenna, rather than relying on a single active element as in some other antenna designs. The elements of the Log-periodic antenna are arranged in decreasing lengths along the boom, which is the horizontal support structure of the antenna. This variation in element lengths is crucial, as it allows the antenna to effectively cover a wide range of frequencies.

Broadband Capabilities and Functionality

The electrical functionality of a Log-periodic antenna is that of an active broadband array. This means that it is capable of operating efficiently over a wide spectrum of frequencies, simulating the performance characteristics of a series of full-sized two or three-element Yagi antennas. The Yagi antenna is known for its directional properties and gain, and while the Log-periodic antenna shares some visual similarities with the Yagi design, its operational principles and capabilities differ significantly.

Operational Mechanism

The Log-periodic design operates in a manner that is quite similar to that of a three-element Yagi antenna. However, what sets it apart is the way in which the dipole elements are fed. In a Log-periodic antenna, the elements are connected through a common transmission line, allowing for alternate feeding of the dipoles. This connection is vital as it enables the antenna to shift its active region in response to changes in frequency. As the frequency increases, the active region of the antenna shifts forward along the array, moving towards the shorter elements. This dynamic adjustment ensures that the antenna remains efficient across its operational bandwidth.

Frequency Response and Active Regions

One of the most intriguing aspects of the Log-periodic antenna is its ability to handle changes in operational frequency. As the frequency shifts upward, the active region of the antenna does not remain static; instead, it migrates among the various elements. This means that not all elements are active at any given moment, allowing the antenna to maintain performance across different frequencies. The design cleverly utilizes the principle of having some elements act as passive radiators, which play a crucial role in enhancing the overall signal reception and transmission capabilities of the antenna.

A little known fact is that a HF LPDA 30 -10 actually works on 6 meters, but the pattern is not straight off the front, the main lobe on 6 meters in split and has two smaller lobes about 45 degrees each off the front with about the same gain as the main beam was on 10 meters. but Mike Staal (K6MYC) of M2 and Mark Chouinard (K5YAC) at Tennadyne, have told me that they know it, but don't advertise it, because the lobe is not direct off the front, it is just too confusing. I have used this to my advantage for years. Being in Kansas I can work stations in both the NE and SE, or NW and SW at the some time, and not move the Array.

Structural Similarities and Differences with Yagi Antennas

Although the Log-periodic antenna (yagi-style log periodic) might look similar to a Yagi antenna due to its linear element arrangement and boom, their electrical properties and operational mechanics are fundamentally distinct. The Log-periodic design includes both active and passive elements, enabling a more intricate signal interaction that can enhance performance across various applications. The passive elements help direct and reflect signals towards the active elements, thereby boosting the antenna system's overall gain and efficiency. In essence, the Log-periodic antenna is a versatile and efficient broadband design, using half-wave dipoles of different lengths to cover a wide frequency range. Its unique feeding mechanism and ability to dynamically shift the active region make it a powerful tool for diverse communication needs, setting it apart from traditional designs like the Yagi.

A complex impedance matching setup is unnecessary for driving an LPDA, with most using a 300-ohm balanced or 50-ohm unbalanced feed system.

With a gain of +6 dB and when installed at half a wavelength above the ground, it achieves 6 dB more ground gain, about 2 dB more than a Hex-Beam, with significantly more front-to-back ratio. Operating over bandwidths of 2:1 to 4:1 is common, with a nominal half-power beam width of 65 degrees. In ice or hail storms, the Hex-beam's wire may break. A 10:1 bandwidth is possible in VHF/UHF designs and for TV reception. The wide bandwidth is a significant advantage over a Yagi and other antenna types, without traps, wires, or moving parts that could fail.

a view of one of K0UO's very big 40 to 10 meters, Log LPDA beam antenna son a giant 200 foot tower that is 10 foot wiide on the sides, General Steven Walz 1200 acre world largest antenna site and test range, k0uo ham radio station k0uo,
miles of antennas for ham radio
dozens of tall antenna support structures, like FCC registered towers up to 195 foot, numerous 100 foot wood powerline poles, concrete silos, and portable mobile tower view from the top of the FCC TOWER NUMBER AR #1216715 on the k0uo antenna test and rhombic farm is a big gun and contester dream station the biggest ham station with the highest gain antennas in the world.
Welcome to K0UO's premier ham radio antenna site farm, spanning hundreds of acres dedicated to innovative design and rigorous testing of antennas. The largest in the world, so join me in advancing the field of ham antennas radio with cutting-edge technology and expert guidance. This station has been very competitive, and has won many major worldwide amateur radio contest.
High-Frequency Stock Trading groups should use the rhombic antenna.

The Defense Technical Information Center is RSI's central facility for the collection and dissemination of scientific and technical training information. RSI supplies training and assessment services to the United States and other governments.Welcome to the K0UO Ham Radio Station, home the world's largest antenna site and test range, spanning impressive 1,200 acres. Featuring miles of antennas and towering structures—including FCC-registered reaching up to 195 feet—our facility is a dream destination for serious contester and big gun operators. With numerous -foot wooden powerline poles, concrete silos, and portable mobile towers, the K0UO Rhombic Farm stands out for its significant height and capabilities. Registered under Antenna Structure Registration number 1216715, our station is recognized in the FCC public file, credibility and verification that sets us apart from other so-called big gun ham stations. The station and antenna farm uses very complex highly engineered arrays.

k0uo uses Re-entrant Rhombic array is one of the highest forward gain HF antennas with its 90% efficiency, the highest forward gain of any HF ham antenna. Also a world-class multiple stations, with many large LPDA yagi type beam antennas, 195 to 300 foot towers, and multiple very large wood power-poles. Antennas from 160 meters up to 2 meters. Using the new Icom IC7760 as the main transceivers.

With 1200 acres near by to test and build all types of antennas and tower pole supports, also the largest ham radio station in the world with milrd of wire arrays and many towers, Antenna Test Facility ATF, electromagnetically-quiet area.
Miles of antennas for ham radio
dozens of tall antenna support structures, like FCC registered towers up to 195, to 300 foot on a near by Gypsum hills site, numerous 100 foot wood power-line poles, concrete silos, and portable mobile towers.
The K0UO Rhombic farm and antenna test range is one of the very few ham radio stations that has a tower which is tall enough and required by the FCC to have a registration. The Antenna Structure Registration or ASR tower number is 1216715. So the K0UO site, station, and antenna is in the FCC public file. used in conjunction with RSI Corp of Kiowa KS seehttps://www.rsicorp.com/dtic. Use for DOD and commercial wireless telecommunications groups.

RSI Corp can Handle technical management, RF testing logistics, and integration of measurement instrumentation in collaboration with the facility. The K0UO

highly technical facility used to precisely measure an antenna's performance characteristics, such as its radiation pattern and gain.

the K0UO antenna test range site has significant outdoor acres at the estate, so anechoic test chambers are not needed.

https://www.rsicorp.com/dtic
K0UO's premier ham radio antenna site farm, spanning hundreds of acres dedicated to innovative design and rigorous testing of antennas. The largest in the world, so join me in advancing the field of ham antennas radio with cutting-edge technology and expert guidance. This station has been very competitive, and has won many major worldwide amateur radio contest. .Welcome to the K0UO Ham Radio Station, home the world's largest antenna site and test range, spanning impressive 1,200 acres. Featuring miles of antennas and towering structures—including FCC-registered reaching up to 195 feet—our facility is a dream destination for serious contester and big gun operators. With numerous -foot wooden powerline poles, concrete silos, and portable mobile towers, the K0UO Rhombic Farm stands out for its significant height and capabilities. Registered under Antenna Structure Registration number 1216715, our station is recognized in the FCC public file, credibility and verification that sets us apart from other so-called big gun ham stations. The station and antenna farm uses very complex highly engineered arrays.

K0Uo Steve Walz has number of LPAD Log yagi HF antennas through out the 1200 acres site on 100 to 200 foot towers — **K0UO's old M2 40 Meter Skip-Log at 160 foot, in the 1990s**

Below the Tennadyne in use at K0UO

Unlike many LPDA antennas, the Tennadyne has minimal wind resistance. I've had one installed on a 195 ft tower for 20 years without any maintenance, enduring ice, hail, and numerous 80 mph wind storms.

Mark K5YAC at Tennadyne produces an outstanding antenna.

Visit the Tennadyne website https://www.tennadyne.com/

More info about Tennadyne history and owner

https://www.tennadyne.com/lpda-systems/

https://youtu.be/YJf5A4h-Dns?si=0MGX2FOfEkU6nTA-

BELOW: I am using two Tennadyne Logs, one at 100 feet, installed in 2023. The other at 195 feet installed in 2006

view of of K0uo's cement silo and two towers, one is 100 foot antenna support for the LPDA Log, Rhombic and V Beams, on the onetower on the right is 195 foot with a LPDA beam on General Steven Walz 1200 acre world largest antenna site and test range, k0uo ham radio station k0uo,
miles of antennas for ham radio
dozens of tall antenna support structures, like FCC registered towers up to 195 foot, numerous 100 foot wood powerline poles, concrete silos, and portable mobile tower view from the top of the FCC TOWER NUMBER AR #1216715 on the k0uo antenna test and rhombic farm is a big gun and contester dream station the biggest ham station with the highest gain antennas in the world K0Uo Steve Walz has number of LPAD Log yagi HF antennas through out the 1200 acres site on 100 to 200 foot towers
showing the K0UO Rhombic antenna farm which is the highest forward gain array and largest area on 1200 acres in use by any amateur ham station DX, remote, or contest station in current use any where in the world — **Above:** **Currently my K**0UO Kansas station has two Tennadyne HF LPDA Logs, one installed at 100 feet, new in 2023. The other at 195 feet installed in 2006, that has been through many heavy ice, and +80 mph wind storms over the years.

The Tennadyne Log-Periodic Dipole Arrays (LPDA) are robust and comparable in price and size to a Hex. However, they offer more gain and improved front-to-back ratio, with minimal risk of damage. They feature no traps, lossy coils, wires that could break, or moving parts. Once assembled, the SWR remains low without needing any tuning, and you can extend the mast through the array to mount another antenna, such as a VHF/UHF antenna, on top.

View Currently my K0UO Kansas station has two Tennadyne HF Logs, one installed at 100 feet, new in 2023. The other at 195 feet installed in 2006, that has been through many heavy ice, and +80 mph wind storms over the years.

Above: Is at K8CU, an LPDA stack, at one time I also had a stack, using two T12 Tennadynes.

Below: My antenna in Belize at V31KW, which has been installed for over 35 years, utilizing a Collins Log-periodic 237B-3 RLP/ LPH-1B (LP1002-5/30) setup for 5-30 MHz use, positioned at 90ft. It has withstood several hurricanes over the years. Although a large LPDA, this Log offers no more gain than a Tennadynes on 20 - 10 meters, http://www.collinsradio.org/wp-content/uploads/2022/12/Q3-2018.pdf

Now sold by https://www.usantennaproducts.com/antennas/models-lp-1005-lp-1001-lp-1002/ or https://www.antennas.com/product/lph-1b/

K0UO Very Large collins LPDA array in Belize V31K,W by saltwater very high gain on a 90 foot tower — **V31KW Belize**

View of a Very Large collins 237B-3RLP, LPDA antenna like K0UO uses in Belize V31KW by saltwater very high gain on a 90 foot tower the Log-periodic antenna might look similar to a Yagi antenna due to its linear element arrangement and boom, their electrical properties and operational mechanics are fundamentally distinct. The Log-periodic design includes both active and passive elements, enabling a more intricate signal interaction that can enhance performance across various applications. The passive elements help direct and reflect signals towards the active elements, thereby boosting the antenna system's overall gain and efficiency. In essence, the Log-periodic antenna is a versatile and efficient broadband design, using half-wave dipoles of different lengths to cover a wide frequency range. — **Above: The DOD/FBI/ US Government LPDA standard setup mostly using the** **old Collins** 237B-3 RLP **design, now LPH 1C, or US Products LP-1005AA**

see http://w6dsr.com/LP1005AA/index.html

and http://w6dsr.com/LP1005AA%20Restoration/index.html

View of a Very Large collins 237B-3RLP, LPDA antenna for a Short wave broadcaster like K0UO uses in Belize V31KW by saltwater very high gain on a 90 foot tower — **A Large HF LPDA used for a Short Wave Broadcaster**

Logarithmic Periodic Dipole Antenna Calculator

The ratio of the successive element lengths (L_(n+1)/L_n) be equal to some constant k, and that the distance between elements (d_(n+1)/d_n) also equal k.

See:

https://www.changpuak.ch/electronics/lpda.php

https://hamwaves.com/lpda/en/index.html

https://play.google.com/store/apps/details?id=com.radioacoustick.lpdadesigner&hl=en_US&pli=1

https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1959/11/page11/index.html

https://wb0dgf.com/LPCAD.htm

A view of a large Log LPDA on a 4" boom made of low cost wire — **A wire element 2-30 MHz Log, rated for 25KW**

**A very high gain Log on a mountain top firing down hill**

diagram view of four very large LPDA only one tower , these are make of wire , very low cost to build for anyone. — **Four Direction fixed wire LPDA use for DOD and Commercial HF Networks**

A dawing of a Log-periodic antenna which might look similar to a Yagi antenna due to its linear element arrangement and boom, their electrical properties and operational mechanics are fundamentally distinct. The Log-periodic design includes both active and passive elements, enabling a more intricate signal interaction that can enhance performance across various applications. The passive elements help direct and reflect signals towards the active elements, thereby boosting the antenna system's overall gain and efficiency. In essence, the Log-periodic antenna is a versatile and efficient broadband design, using half-wave dipoles of different lengths to cover a wide frequency range. — **Broadband LPDA Data and Model**

A view of a very large LPDA Log that A friend of mine took this antenna down from a SW Broadcaster in Mexico a few years ago and is planing on installing it at his ham station in east Texas, — A friend of mine took this antenna down from a SW Broadcaster in Mexico a few years ago and is planing on installing it at his ham station in east Texas, if I don't get it before then! Look at the rotator used to turn it.

view of a very large tower and LPDA that A friend of K0uo took this antenna down from a SW Broadcaster in Mexico a few years ago and is planing on installing it at his ham station in east Texas, if I don't get it before then! Look at the rotator used to turn it. the Log-periodic antenna might look similar to a Yagi antenna due to its linear element arrangement and boom, their electrical properties and operational mechanics are fundamentally distinct. The Log-periodic design includes both active and passive elements, enabling a more intricate signal interaction that can enhance performance across various applications. The passive elements help direct and reflect signals towards the active elements, thereby boosting the antenna system's overall gain and efficiency. In essence, the Log-periodic antenna is a versatile and efficient broadband design, using half-wave dipoles of different lengths to cover a wide frequency range. — **A Photo of the Giant when it was in use, just like to one that Vatican Radio uses, so they don't have the only large LPDA, but they claim the largest!**

a view of friend of k0uo who took this LPDA antenna down from a SW Broadcaster in Mexico a few years ago and is planing on installing it at his ham station in east Texas, if I don't get it before then! Look at the rotator used to turn it. — Monstrous Rotor for moving the LPDA

Below: A YouTube of the repair & refurbishing of the LP-1002 Log Periodic Beam Antenna @ the Northern Utah WebSDR 4

https://www.youtube.com/watch?v=hUKQj36iehQ

Northern UT Web SDR Number 5, with an old 10-30 MHz KLM log

https://www.youtube.com/watch?v=f1u_XSx6jn8

A large logarithmic antenna protel radio link ARL531 5-30 MHz being installed

https://youtu.be/4APvcUHFmsw?si=GDrkV3xWm-ACmSPl

Below: A large Log using the old Collins 237B-3 RLP design, now LPH 1C or US Products LP-1005AA

View of a Large metal tower and LPDA use at the Vatican Radio antenna it is large 150 foot but has no more gain than a 3 element yagi — **A Broadcaster Short Wave LPDA**

View of the big 195 ft by 10 ft wide rotating tower with very large 40 meter beams, General Steven Walz 1200 acre at the world largest antenna site and test range, k0uo ham radio station k0uo,
miles of antennas for ham radio
dozens of tall antenna support structures, like FCC registered towers up to 195 foot, numerous 100 foot wood powerline poles, concrete silos, and portable mobile tower view from the top of the FCC TOWER NUMBER AR #1216715 on the k0uo antenna test and rhombic farm is a big gun and contester dream station the biggest ham station with the highest gain antennas in the world. k0uo uses Re-entrant Rhombic array is one of the highest forward gain HF antennas with its 90% efficiency, the highest forward gain of any HF ham antenna. Also a world-class multiple stations, with many large LPDA yagi type beam antennas, 195 to 300 foot towers, and multiple very large wood power-poles. Antennas from 160 meters up to 2 meters. Using the new Icom IC7760 as the main transceivers.

With 1200 acres near by to test and build all types of antennas and tower pole supports, also the largest ham radio station in the world with miles of wire arrays and many towers, Antenna Test Facility ATF, electromagnetically-quiet area.Miles of antennas for ham radio dozens of tall antenna support structures, like FCC registered towers up to 195, to 300 foot on a near by Gypsum hills site, numerous 100 foot wood power-line poles, concrete silos, and portable mobile towers.The K0UO Rhombic farm and antenna test range is one of the very few ham radio stations that has a tower which is tall enough and required by the FCC to have a registration. The Antenna Structure Registration or ASR tower number is 1216715. So the K0UO site, station, and antenna is in the FCC public file. Also a world-class multiple stations, with many large LPDA yagi type beam antennas, 195 to 300 foot towers, and multiple very large wood power-poles. K0Uo Steve Walz has number of LPAD Log yagi HF antennas through out the 1200 acres site on 100 to 200 foot towers. showing the K0UO Rhombic antenna farm which is the highest forward gain array and largest area on 1200 acres in use by any amateur ham station DX, remote, or contest station in current use any where in the world — K0UO Steve Walz has number of LPAD Log yagi HF antennas through out the 1200 acres site on 100 to 200 foot towers

view of one of the K0UO's Very large rotator motors to turn the big LPDA antenna on the 200 foot tower — Above is the very huge prop pitch motor which turned the K0UO 40 to 10 meter large LPDA Log yagi, the steel base is made from 4" by 12" steel beam

Calculator to build a LPDA

Log Periodic Dipole Array

LPDA Links

https://www.realhamradio.com/Log_Periodic.htm

https://shop.hamsphere.com/product_info.php?products_id=98224

https://www.google.com/search?q=log+periodic+antenna+vs+yagi&client=firefox-b-1-d&sca_esv=04b81a3a06aed432&sca_upv=1&biw=1366&bih=615&sxsrf=ADLYWIIbCk1IdQz2X84GfmPIRPc2KB1dFQ%3A1720893270343&ei=Vr-SZqnLFLbdwN4P6rGYyAI&oq=Log+periodic+antenna+&gs_lp=Egxnd3Mtd2l6LXNlcnAiFUxvZyBwZXJpb2RpYyBhbnRlbm5hICoCCAQyChAjGIAEGCcYigUyChAjGIAEGCcYigUyBBAjGCcyChAAGIAEGBQYhwIyBRAAGIAEMgUQABiABDIFEAAYgAQyBRAAGIAEMgoQABiABBhDGIoFMgUQABiABEjuNlDbEVjbEXACeACQAQCYAcQBoAGUAqoBAzEuMbgBAcgBAPgBAZgCA6ACacICChAAGLADGNYEGEeYAwCIBgGQBgiSBwEzoAflEA&sclient=gws-wiz-serp#fpstate=ive&vld=cid:d20d9dbc,vid:KMmpgqDiIlk,st:0

https://www.google.com/search?q=Log+periodic+antenna&client=firefox-b-1-d&sca_esv=04b81a3a06aed432&sca_upv=1&sxsrf=ADLYWILJHXSeSeBgkg0spsW5WLVuQWzpWw:1720894525878&ei=PcSSZpynNf2rur8Px_SruA8&start=20&sa=N&sstk=AagrsuhzzgmVDbxLpbMek5te1GJmZZyemaTeBqBWgxEVaAk5BVwys9k6Oi6sB_pqXWRdl7k7cMgPC0UhxlM8ts80sBoHvxH8H8T3isCxaRTXOBeruywcp-zEPHtljXSv4mKe&ved=2ahUKEwjcuaTXz6SHAxX9le4BHUf6Cvc4ChDy0wN6BAgEEAc&biw=1366&bih=615&dpr=1#fpstate=ive&vld=cid:8a5557d7,vid:KUyJYhDvGnw,st:0

COMPARISON OF COLLINS LOG -PERIODIC ANTENNA AND

MILITARY RHOMBIC ANTENNAS, SEE PAGE 79 UP https://w1op.com/237/Collins%20Antennas/Collins%20Antennas%201960.pdf

Install of a large Log

https://www.youtube.com/watch?v=4hEElTGNYAM

The K0UO antenna test range site utilizes the 4KS Walz airport known as "Antenna University", and its surrounding area as a practical learning environment for Scientific, Technical, Engineering, & Mathematics (STEM) antenna projects in an outdoor real-world setting. If your group has a University aerospace or antenna research STEM program, let me know.

TO SEE the complete K0UO antenna Blog list check @ https://www.k0uo.com/k0uo

MY Work https://en.wikipedia.org/wiki/RSI_Corporation