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 Post subject: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenna
PostPosted: Thu Jun 12, 2008 12:25 am 
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NSN# - 5985-01-498-0332

The model COM201B is a vertically polarized, omnidirectional antenna specifically designed for quick deployment and ease of operation. A unique tripod leg structure allows the antenna to be mounted directly on the ground or mounted on a standard communications mast. The antenna covers the 30 to 88 MHz band without external tuning.

Features

* 30-88 MHz Frequency Range
* 200 Watts Average
* Vertically Polarized, Omnidirectional
* Lightweight Rugged Construction

Similar Antennas:

The Model 231 is a vertically polarized, omnidirectional antenna specifically designed to meet rigorous, environmental and mechanical conditions encountered in a military environment. It provides VHF communications for a range of military vehicles and can be used with any radio that operates within its 30-88 MHz frequency.

The model COM228 is a stacked, two port omnidirectional antenna specifically designed for quick deployment and ease of operation. The antenna is mounted in a stacked configuration for maximum isolation, and covers the 30-88 MHz band without external tuning.

The model COM209 is a vertically polarized, omnidirectional, low power dipole antenna. Specifically designed for ground-to-air and point-to-point communications. The antenna is provided with an integral base mount with recessed RF connector for ease of installation. Frequency coverage is from 225 - 400 MHz without external tuning.


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenna
PostPosted: Tue Sep 09, 2008 2:15 pm 
i have recently tried to purchase the com 201b but on fedlog it says that the nsn is no longer availible and has been discontinued w/o replacement. does any one out there know where i can get teh equivilent to the 201b and not the 231 which i can get no problem.


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenna
PostPosted: Fri Oct 24, 2008 5:19 pm 
Re: COM201B
How many do you need? Delivery times?
Equivelents ok?
[email protected]


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenna
PostPosted: Tue Mar 17, 2009 6:44 pm 
hEY YOU ARE GOING TO OPEN PURCHASE THEM WORK WITH YOUR MMO AND SUPPLY TO FIND OUT HOW


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenna
PostPosted: Thu Jun 11, 2009 10:49 pm 
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Posts: 75
Here's a great article from FT Gordon about the COM 201 vs the OE-254:

http://www.gordon.army.mil/ocos/ac/Edit ... SMCnet.htm

Marines adopt new broadband very-high-frequency antenna for combat-net radios -- should the Army follow suit?

by David Fiedler and Edward Farmer

Historically, to increase transmitted signal strength, coverage area and point-to-point ground distance for tactical very-high-frequency (30-88 megahertz) radio systems, the Army and Marine Corps turned to elevated (30-foot mast-mounted) ground-plane and biconic antennas such as the widely used RC-292 and OE-254 (following figures). Both antennas perform acceptably electrically but are much too heavy and complicated for today’s fast-moving operations, particularly for light infantry, Special Forces and airborne/airmobile units. (See related information on RC-292 and OE-254 characteristics and problems.)


The RC-292 is a general-purpose, stationary, ground-plane antenna used to increase the transmission/reception range of tactical frequency-modulation radio sets. The radiating and ground-plane elements must be adjusted to the proper length for a particular operating frequency. The RC-292’s technical characteristics are: frequency range, 20-76 mhz; planning range, about twice the planning range of a radio set using a quarter-wave whip antenna; height when erected, 11.28 to 12.56 meters (37 to 41.2 feet); and weight, about 19.5 kilograms (43 pounds).

The OE-254 is a general-purpose, stationary, broadband, omni-directional antenna used to extend the range of tactical FM radio sets. Under normal field conditions, the antenna will be mast-mounted. Once installed, the OE-254 doesn’t have to be taken down for adjustment when a new frequency band is assigned to the radio net. The OE-254’s technical characteristics are: frequency range, 30-88 mhz; planning range, 57.9 kilometers (36 miles) over average terrain or 48.3 kilometers (30 miles) over difficult terrain; radio-frequency power capability, 35 watts nominal; antenna-erection time (one person), 15 minutes; height when erected, 12.8 meters (42 feet); input impedance to radio, 50 ohms; and weight, 20.4 kilograms (45 pounds).
Also, they both contain many separate parts that are easily lost. Both require much too much time to erect and tear down. Assembling and adjusting the mast, and assembling the multisection screw-together antenna elements that form both antennas, take most of the installation time.

The Marines have found another answer; now we need a better way.

Antennas compared

A new antenna is available that has ground-plane and biconic radiation characteristics but is designed specifically to improve both electrical and tactical characteristics. The Marine Corps and other government agencies are procuring this antenna from Atlantic Microwave Corporation.

Commercially named the COM-201 (NSN# 5985-01-450-3798, USMC PN 960-15A 1008), the antenna is a 30-88 mhz, vertically polarized, omni-directional, ground-plane type. It’s unique because it’s designed so it can mount directly on the ground using a built-in “snap out” tripod that’s also the antenna’s complete ground-plane structure. The COM-201 is also fitted for mast-mounting on standard antenna masts if a more elevated antenna is needed. The eye fitting at the antenna’s top facilitates suspending it from buildings or trees when a mast isn’t available but more height is desired.

One of the COM-201’s best features, however, is that the antenna breaks down into five parts that can be assembled in less than a minute.

While the OE-254 gains bandwidth by simulating frequency-independent biconic construction, the COM-201 gets its broadband characteristics (variable standing-wave ratio less than 3-to-1 across 30-88 mhz) by using large-diameter elements and a very well-designed broadband matching network built into the antenna base at the feedpoint. When the COM-201 and OE-254 antennas are modeled using the EZNEC-PRO implementation of the NEC-4.1 antenna-analysis software, they show similar frequency response, gain and antenna patterns when both are elevated at 30 feet.

At the high end of the frequency range, the OE-254 shows some overhead modes that waste useful signal power for desired ground communications. Energy at these high angles is generally produced at the expense of radiation on the much more tactically useful low angles, and therefore it’s detrimental to good communications. The COM-201 with its lower takeoff angles delivers more energy (gain) at the radio horizon to make it more useful in ground-to-ground operations.

COM-201 better

Why should the COM-201 be considered to replace existing antennas? Part of the answer lies in its mechanical design. The antenna is designed with quick deployment and ease of operation in mind. The unique tripod metal-tube leg-structures that serve as both mount and electrical ground plane allow the antenna to be installed directly on the ground or atop roofs, shelters, bunkers, etc. (Care should be taken to keep the radiating element vertical to the ground to avoid distorting the antenna-radiation pattern.)

When time and situation permit, the antenna has the fittings required so it can be mounted on standard or makeshift masts, or roped into trees and buildings to gain the advantages of increased height. The antenna can be moved assembled, partially assembled or broken down. The antenna’s active element has a threaded interconnect at the midpoint to reduce its disassembled length to only 36 inches.

The tripod/ground-plane radials telescope and can either be removed or folded up parallel to the active element. This results in a package 36 by 10 inches weighing about 10 pounds. If deployed on its tripod/ground plane, the COM-201 needs only a few feet of coaxial cable to connect it to a radio. This is a feature not available with other antennas.

At platoon and company level, the load reduction of about 30 pounds (when compared to the OE-254) is a very attractive feature that will allow units who couldn’t previously afford to carry a more efficient antenna to do so by using the COM-201. Communications distance loss (if any) generated by locating antennas close to the earth is less of a factor at these lower echelons where distance requirements are shorter to begin with.

In most cases, overall results will be much better because more effective ground-mounted COM-201s can replace the far less efficient 10-foot or three-foot standard-issue manpack vertical antenna with minimal additional effort.

Part of the answer also lies in the COM-201’s electrical- and signal-radiation characteristics. The first thing one notices about the COM-201 antenna’s construction is that the radiating element has a much wider diameter than anyone familiar with our current antennas might expect. This is because increasing the diameter at a constant length (increasing the distance/length ratio) has the effect of decreasing the electrical reactance of the antenna’s elements, which, in turn, increases the frequency range (bandwidth) over which the antenna can be efficiently operated.

The “why” of this takes a bit of explanation. At radio frequencies, all conductors (for example, antennas) inherently have resistance, capacitance and inductance. The resistance is made up of two components which we call “loss resistance” and “radiation resistance.” Loss resistance comes from the flow of radio-frequency electrical current through the antenna’s elements and connections. This energy is dissipated as heat, isn’t useful for communications, and is negligible small in antennas such as these. Radiation resistance accounts for the portion of the energy we apply to the antenna that actually does what we’re trying to do: produce an electromagnetic field and get a signal into the air.

Capacitance and inductance present in an antenna structure produce an effect similar to resistance that we call “reactance.” Reactance opposes the flow of current, as does resistance, but doesn’t result in lost energy since the energy is stored in the inductive field or as electric charge on the capacitive structure.

Taken together, an antenna’s resistance and reactance are called its “impedance.” By definition at the resonance frequency, the inductive reactance and capacitive reactance are equal in magnitude and opposite in phase; consequently they cancel each other, and the antenna presents a pure resistive load (the radiation resistance) to the transmission line and radio. At the resonance frequency, the pure resistive electrical load causes the antenna to be the most efficient radiator of signal possible for that structure.

As the frequency of operation strays above the resonant frequency for the antenna, the antenna begins to have inductive reactance in addition to its resistance. When the frequency strays below the resonant frequency for the antenna, the antenna begins to appear capacitive. Capacitive or inductive reactance not canceled in an antenna circuit reduces the effective radiated power of the signal the antenna generates.

All this becomes particularly interesting when frequency hopping with radios such as Single-Channel Ground and Airborne Radio System because the bandwidth of an antenna – that is, the range of frequencies over which it operates efficiently – is proportional to the ratio of its resistance to reactance. The smaller an antenna’s reactance, the wider its frequency bandwidth.

The COM-201’s physical construction is such that the diameter-to-length ratio is optimized to produce radiation (signal) across the 30-88 mhz frequency band using a structure that has reasonable physical size and radiation-efficiency characteristics. This optimized construction produces more signal (gain) and lower takeoff angles for the COM-201 when compared to an OE-254 at the same height, as the plots show. This means better electrical performance as well as better mechanical performance can be expected from the COM-201 under tactical conditions.

Another part of the answer lies in how the COM-201 electrically “matches” its complex antenna impedance (resistive, capacitive and inductive components) to the transformed 50-ohm impedance of the radio and transmission line to reduce reflected power (voltage SWR) and produce maximum radiated power. To do this, a matching network is incorporated at the antenna’s feedpoint. It provides the inductive and capacitive reactance necessary to compensate for the antenna’s inherent reactance as the operating frequency varies over the 30-88 mhz frequency range. As you can see from the following figures, the network transforms the antenna’s complex impedance into a 50-ohm resistive impedance that closely matches the radio and transmission-line impedances and produces a VSWR of less than 3-to-1 across the frequency range.


The network transforms the antenna's complex impedance into a 50-ohm resistive impedance.

Comparison of tuned COM-201 vs. untuned antenna.
Since deploying the OE-254 antenna in 1978, the Army has had to live with the mechanical and electrical shortfalls inherent in its design. The OE-254 antenna was clearly the best available at that time, and it did well as we moved the Army from the AN/VRC-12 family of single-channel radios to the SINCGARS family of frequency-hopping equipment. The OE-254’s 24 years of service and the huge number of antennas fielded prove the antenna worked well; however, time marches on. Just as we’re not driving the same vehicles and shooting the same weapons we did in 1978, we shouldn’t be using the same field antennas.

The authors believe the Marine Corps made a good decision to adopt the COM-201, but we’re not advocating change for change’s sake. There have been real advances in antenna technology over the last 24 years. The Marines’ successful use of the COM-201 shows that if nothing else, the antenna will provide, at the least, a better physical package since the COM-201 is quicker to deploy and has far fewer small parts to lose or break. A soldier’s ability to set up the COM-201 without need of a mast is a great tactical advantage – particularly in the type of mobile warfare, urban warfare and homeland-defense operations we’re now conducting. Another bonus the COM-201 provides is the higher gain and the lower takeoff angles to help improve tactical combat-radio operations. The Army needs to very seriously consider following the Marines’ lead when replacing our aging stocks of these types of antennas.

Mr. Fiedler – a retired Signal Corps lieutenant colonel – is an engineer and project director at the project manager for tactical-radio communications systems, Fort Monmouth, N.J. Past assignments include service with Army avionics, electronic warfare, combat-surveillance and target-acquisition laboratories, Army Communications Systems Agency, PM for mobile-subscriber equipment, PM-SINCGARS and PM for All-Source Analysis System. He’s also served as assistant PM, field-office chief and director of integration for the Joint Tactical Fusion Program, a field-operating agency of the deputy chief of staff for operations. Fiedler has served in Army, Army Reserve and Army National Guard Signal, infantry and armor units and as a Department of the Army civilian engineer since 1971. He holds degrees in both physics and engineering and a master’s degree in industrial management. He is the author of many articles in the fields of combat communications and electronic warfare.

Mr. Farmer is a Vietnam-era Signal soldier and former lieutenant colonel in California’s State Military Reserve, where he ran intrastate emergency communications. He’s a professional engineer, has an extra-class amateur radio license and is president of EFA Technologies, Inc., in Sacramento, Calif. He has a bachelor’s degree in electrical engineering and a master’s in physics, both from California State University. He has published three books and more than 40 articles, holds four U.S. patents and is a frequent guest speaker at communications and antenna-oriented conferences.

Acronym QuickScan
FM – frequency modulation
Mhz – megahertz
PM – project manager
SINCGARS – Single-Channel Ground and Airborne Radio System
SWR – standing-wave ratio
VHF – very high frequency
VSWR – voltage standing-wave ratio


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenna
PostPosted: Wed Oct 14, 2009 11:58 am 
Does anyone have a TM for this?


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenna
PostPosted: Sat Aug 07, 2010 9:53 pm 
Hello,

I'm Justin Genest, the Direct Military POC (Sales Applications Enginer) for Cobham Sensor Systems-Bolton in Bolton, Massachusetts. We are the division of Cobham in North America that manufactures the COM201B and other quick deployable single and multi-band antennas.

We do have a pdf version of this TM, which I can get out to anyone who request it from me at the info below. Please help get the word out about this antenna and contact me with any questions you might have. I'll be happy to provide additional information about this or any of our other antennas.


Justin



Justin Genest
Sales Applications Engineer
Cobham Sensor Systems
Sensor Electronics - Bolton
[email protected]
(978) 779 - 7002


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenn
PostPosted: Mon Nov 05, 2012 7:18 pm 
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Posts: 1
I need a part listing for a comm 201B. I am missing one of the nipples that hold the ley in place and need to order a new one.

SSG D.


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenn
PostPosted: Thu Jul 16, 2015 2:08 am 
I have done some field testing at NTC while my unit was conducting training. My findings follow.

Our retrans element had a dramatic range improvement when a OE-254 was used on the receive side and a COM-201 was used on the transmit side.

My explanation for this improvement lies in the examination of the COM-201 radiation pattern which appears to present a higher gain than the OE-254 in the more horizontal region.

Utilizing the OE-254 on the receive side allowed us to improve reception of distant signals over the COM-201. This application proved itself on numerous setups where we had chosen the COM-201 instead(multiple 201s were tested). On 3 separate occasions the COM-201 allowed us to reach out to very distant stations but prevented us from receiving signals from those same stations. However, when we switched to the OE-254 we were able to receive intelligible comms from those same stations with an expected reduction in transmitting capability. I attribute this to the increased conductivity of the OE-254s antenna elements. Although I am no expert I use this experience to set up and establish retrans missions as a rule.

I don't check this forum very often but if anyone has any questions please feel free to email me at [email protected]


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 Post subject: Re: 5985-01-498-0332, COM201B Lightweight VHF And UHF Antenn
PostPosted: Sat Aug 01, 2015 11:45 am 
commojitsu wrote:
I have done some field testing at NTC while my unit was conducting training. My findings follow.

Our retrans element had a dramatic range improvement when a OE-254 was used on the receive side and a COM-201 was used on the transmit side.

My explanation for this improvement lies in the examination of the COM-201 radiation pattern which appears to present a higher gain than the OE-254 in the more horizontal region.

Utilizing the OE-254 on the receive side allowed us to improve reception of distant signals over the COM-201. This application proved itself on numerous setups where we had chosen the COM-201 instead(multiple 201s were tested). On 3 separate occasions the COM-201 allowed us to reach out to very distant stations but prevented us from receiving signals from those same stations. However, when we switched to the OE-254 we were able to receive intelligible comms from those same stations with an expected reduction in transmitting capability. I attribute this to the increased conductivity of the OE-254s antenna elements. Although I am no expert I use this experience to set up and establish retrans missions as a rule.

I don't check this forum very often but if anyone has any questions please feel free to email me at [email protected]


I have found the OE-254 to be great at receiving and very good at coverage in hilly terrain. I have used both antennas extensively over the past 9 years and still favor the OE-254 feed cone most of the time. I have been able to push farther with the COM201 though. My team in Iraq in 2009 put a section of OE-254 mast on top of a QEAM mast and where able to push almost 50+miles in the early morning. Some how we manage this with two cables attached.


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