https://urgentcomm.com/wp-content/themes/ucm_child/assets/images/logo/footer-new-logo.png
  • Home
  • News
  • Multimedia
    • Back
    • Multimedia
    • Video
    • Podcasts
    • Galleries
    • IWCE’s Video Showcase
    • IWCE 2022 Winter Showcase
    • IWCE 2023 Pre-event Guide
  • Commentary
    • Back
    • Commentary
    • Urgent Matters
    • View From The Top
    • All Things IWCE
    • Legal Matters
  • Resources
    • Back
    • Resources
    • Webinars
    • White Papers
    • Reprints & Reuse
  • IWCE
    • Back
    • IWCE
    • Conference
    • Special Events
    • Exhibitor Listings
    • Premier Partners
    • Floor Plan
    • Exhibiting Information
    • Register for IWCE
  • About Us
    • Back
    • About Us
    • Contact Us
    • Advertise
    • Terms of Service
    • Privacy Statement
    • Cookie Policy
  • Related Sites
    • Back
    • American City & County
    • IWCE
    • Light Reading
    • IOT World Today
    • Mission Critical Technologies
    • TU-Auto
  • In the field
    • Back
    • In the field
    • Broadband Push-to-X
    • Internet of Things
    • Project 25
    • Public-Safety Broadband/FirstNet
    • Virtual/Augmented Reality
    • Land Mobile Radio
    • Long Term Evolution (LTE)
    • Applications
    • Drones/Robots
    • IoT/Smart X
    • Software
    • Subscriber Devices
    • Video
  • Call Center/Command
    • Back
    • Call Center/Command
    • Artificial Intelligence
    • NG911
    • Alerting Systems
    • Analytics
    • Dispatch/Call-taking
    • Incident Command/Situational Awareness
    • Tracking, Monitoring & Control
  • Network Tech
    • Back
    • Network Tech
    • Interoperability
    • LMR 100
    • LMR 200
    • Backhaul
    • Deployables
    • Power
    • Tower & Site
    • Wireless Networks
    • Coverage/Interference
    • Security
    • System Design
    • System Installation
    • System Operation
    • Test & Measurement
  • Operations
    • Back
    • Operations
    • Critical Infrastructure
    • Enterprise
    • Federal Government/Military
    • Public Safety
    • State & Local Government
    • Training
  • Regulations
    • Back
    • Regulations
    • Narrowbanding
    • T-Band
    • Rebanding
    • TV White Spaces
    • None
    • Funding
    • Policy
    • Regional Coordination
    • Standards
  • Organizations
    • Back
    • Organizations
    • AASHTO
    • APCO
    • DHS
    • DMR Association
    • ETA
    • EWA
    • FCC
    • IWCE
    • NASEMSO
    • NATE
    • NXDN Forum
    • NENA
    • NIST/PSCR
    • NPSTC
    • NTIA/FirstNet
    • P25 TIG
    • TETRA + CCA
    • UTC
Urgent Communications
  • NEWSLETTER
  • Home
  • News
  • Multimedia
    • Back
    • Video
    • Podcasts
    • Omdia Crit Comms Circle Podcast
    • Galleries
    • IWCE’s Video Showcase
    • IWCE 2023 Pre-event Guide
    • IWCE 2022 Winter Showcase
  • Commentary
    • Back
    • All Things IWCE
    • Urgent Matters
    • View From The Top
    • Legal Matters
  • Resources
    • Back
    • Webinars
    • White Papers
    • Reprints & Reuse
    • UC eZines
    • Sponsored content
  • IWCE
    • Back
    • Conference
    • Why Attend
    • Exhibitor Listing
    • Floor Plan
    • Exhibiting Information
    • Join the Event Mailing List
  • About Us
    • Back
    • About Us
    • Contact Us
    • Advertise
    • Cookie Policy
    • Terms of Service
    • Privacy Statement
  • Related Sites
    • Back
    • American City & County
    • IWCE
    • Light Reading
    • IOT World Today
    • TU-Auto
  • newsletter
  • In the field
    • Back
    • Internet of Things
    • Broadband Push-to-X
    • Project 25
    • Public-Safety Broadband/FirstNet
    • Virtual/Augmented Reality
    • Land Mobile Radio
    • Long Term Evolution (LTE)
    • Applications
    • Drones/Robots
    • IoT/Smart X
    • Software
    • Subscriber Devices
    • Video
  • Call Center/Command
    • Back
    • Artificial Intelligence
    • NG911
    • Alerting Systems
    • Analytics
    • Dispatch/Call-taking
    • Incident Command/Situational Awareness
    • Tracking, Monitoring & Control
  • Network Tech
    • Back
    • Cybersecurity
    • Interoperability
    • LMR 100
    • LMR 200
    • Backhaul
    • Deployables
    • Power
    • Tower & Site
    • Wireless Networks
    • Coverage/Interference
    • Security
    • System Design
    • System Installation
    • System Operation
    • Test & Measurement
  • Operations
    • Back
    • Critical Infrastructure
    • Enterprise
    • Federal Government/Military
    • Public Safety
    • State & Local Government
    • Training
  • Regulations
    • Back
    • Narrowbanding
    • T-Band
    • Rebanding
    • TV White Spaces
    • None
    • Funding
    • Policy
    • Regional Coordination
    • Standards
  • Organizations
    • Back
    • AASHTO
    • APCO
    • DHS
    • DMR Association
    • ETA
    • EWA
    • FCC
    • IWCE
    • NASEMSO
    • NATE
    • NXDN Forum
    • NENA
    • NIST/PSCR
    • NPSTC
    • NTIA/FirstNet
    • P25 TIG
    • TETRA + CCA
    • UTC
acc.com

content


Elucidations and explorations

Elucidations and explorations

The September 2000 "Technically Speaking" column, on transmitter noise and receiver desense, requires some clarification, based on feedback from an experienced
  • Written by Urgent Communications Administrator
  • 1st January 2001

The September 2000 “Technically Speaking” column, on transmitter noise and receiver desense, requires some clarification, based on feedback from an experienced reader. His comments provide additional useful insights to topics covered in the past few months as well. This month we also have a question from a reader regarding contact corrosion problems with paging transmitters. If you have comments, questions, suggestions or information that you feel might benefit the readership of MRT, please feel free to send them to me at the mailing address or email address listed below, or submit them via the MRT Web site, www.mrtmag.com. Also, if you have found a good Web site that might offer tutorials or calculation tools that would benefit readers of MRT, please pass them along to me. The good leads will be published on the MRT Web site or in future columns.

First up is an excellent response to some of the topics covered in the September 2000 issue by William J. Kessler, P.E. Kessler has more than 40 years of experience in electronic and communications engineering, including university-level teaching, research projects, and extensive consulting engineering. He is a principal in Kessler and Gehman Associates, Telecommunications Consulting Engineers. His feedback concerns the measurement and/or calculation of isolation between antennas. You may wish to refer back to the figures used in the September column, which appeared on pages 18 and 20.

Kessler writes [text edited for space; figures are reprinted on page 20.-Ed.]:

“I noticed the following omission regarding the application of the free-space isolation formula:

“This formula is applicable only when both antennas are located well inside the Fraunhofer region of each antenna. The Fraunhofer region, (far field region) is that region where the propagated wave front from one antenna to the other antenna is essentially a plane wave.

“By contrast, the Fresnel region (near field region) is where the propagated wave front adjacent to the receiving antenna is spherical. This can result in an unacceptable phase variation of the signal at the receiving antenna due to radiation of the signal from different parts of the transmitting antenna. The line of demarcation between the near field and far field region is rather diffuse. However, most engineers have accepted the demarcation distance (d) to be equal to or greater than twice the dimension (D) of the larger antenna squared divided by the operating wavelength (l). That is:

“Therefore, when referring to the application of the free-space attenuation formula, the restriction that the distance separating the two antennas should be equal to, or greater than, the value of d as given in the previous equation.

“Your Figure 1 example is correct in that the two 6dB gain antennas operating at 150MHz are 500 feet apart. A 6dB-gain antenna at 150MHz (l 5 6.56 feet) would be at least 20 feet long. Therefore, according to the free-space propagation formula, the minimum separation distance would be:

“Clearly, the 500-foot spacing in your example in Figure 1 exceeds the minimum required horizontal separation between the antennas.

“With regard to Figure 2, which illustrates the vertical separation (V) between two gain antennas as measured from center-to-center, not all engineers are in agreement on how the spacing should be measured. Some engineers measure the separation distance between the top of the lower radiating element and the bottom of the upper radiating element. For antennas exhibiting gains of 6dB to 9dB, the substitution of the smaller distance into the formula would yield a lower isolation between the antennas than the substitution of the larger center-to-center measure.

Perhaps these engineers simply want to play it safe and use the separation measure that yields the lowest isolation figure. The problem I see with the end-to-end separation measure is that it yields an isolation figure that is independent of the size or gain of the vertically spaced antennas. On the other hand, I have reason to believe that the isolation figure calculated using the center-to-center separation distance between high-gain antennas yields a calculated attenuation (isolation) that is too high.

“I have calculated the isolation between a single dipole and a gain antenna (with as many as eight dipoles) by separately calculating the power coupled into the single dipole from each of the dipole arrays, ranging from two dipoles to eight dipoles and summing the result. In each case, the resulting isolation between the antennas falls between the calculated values for the end-to-end and the center-to-center separation measurement. As a result, I now calculate the isolation using the formula for both the end-to-end and center-to-center measures and use the average of the two.

“Although I agree with your statement in the Figure 3 caption that it is better to measure the isolation between two antennas that are spaced both vertically and horizontally, there is a formula for calculating the isolation for this case, where:

S 5 slant isolation.

V 5 vertical isolation.

H 5 horizontal isolation.

u 5 angle in degrees as defined in drawing.

“The formula appears reasonable because for terminal values of u it reverts to the horizontal separation formula for u 5 0 and the vertical separation formula when u 5 90.”

Kessler also included a graph comparing different methods of determining the isolation between collinear antennas or arrays. The graph is shown on page 18.

The next comment comes from a reader whose question is printed here in hopes of triggering some feedback with suggestions and “what you do” to deal with a common problem. Here is his question:

“We are a paging company that has about 2,000 Motorola Nucleus transmitters throughout the USA. The Nucleus has an external battery that keeps the exciter and controller running when there is a power failure. The printed circuit board contacts on the power supply that provide the charging for the external batteries are gold- plated and the connector is tinned. We have been having lots of problems with corrosion and reduction with that connection. The connection becomes a high resistance. The batteries charge OK, but when the power fails and the controller needs the 2A to run, the resistance causes the station to reset.

“Someone suggested we use Stabilant 22A to eliminate the corrosion problem. They claimed it worked great when they worked for Motorola. Motorola will not dig into this because they discontinued the product. Do you have any suggestions on how to deal with the corrosion problems?”

OK readers, if you have any suggestions that might help a fellow reader with this problem, please email me at the addresses given, and I will pass the information along to the readership in a future column.

You are always invited to use this column as a forum to pass along information, ideas and suggestions that might benefit your fellow technicians working in the land mobile radio field.

Until next time – stay tuned!

Tags: content

Most Recent


  • Elucidations and explorations
    Newscan: Securing the Internet of Things is quite a challenge
    Also: EWA requests dismissal of 900 MHz applications; TIA names tech and policy priorities for 2014; IJIS Institute names Shumate Award winner; App makes bus waits more tolerable; a Blackberry comeback may be in the offing.
  • Elucidations and explorations
    Newscan: FCC certifies Carlson Wireless's white-space radio
    Also: Congress looks to revamp telecom law; Obama to place some restraints on surveillance; IEEE to study spectrum-occupancy sensing for white-spaces broadband; Major Swedish transport operator opts for Sepura TETRA radios; RFMD to partner on $70 million next-generation power grid project; NENA opens registratiuon for "911 Goes to Washington."
  • Elucidations and explorations
    Newscan: A look at the critical job of 911 dispatchers
    Also: NYC launches website for tracking 911 response times; Oregon implements 911 on pre-paid cell phones; LightSquared wants to keep spectrum assets; Harris receives multiple government orders; FCC extends rebanding financial reconciliation deadline; Zetron gear at core of communications system upgrade; Ritron debuts wireless access control system; EWA seeks policy review of VHF vehicular repeater system deployments.
  • Elucidations and explorations
    Newscan: Average peak data rates of 144 MB/s average realized in tests with CAT 4 LTE device
    Also: Verizon, T-Mobile to swap unused spectrum to improve coverage; Internet giants oppose surveillance--but only when the government does it; FCC Chairman says incentive auction will be delayed until middle of 2015; FCC chair announces staff appointments; Alcatel-Lucent names Tim Krause as chief marketing officer; New Jersey county deploys TriTech CAD system; Toronto airport deploys 26-position Zetron console system;

Leave a comment Cancel reply

To leave a comment login with your Urgent Comms account:

Log in with your Urgent Comms account

Or alternatively provide your name, email address below:

Your email address will not be published. Required fields are marked *

Related Content

  • RugGear: Contributing to the future of mission-critical broadband communication review and market vision
  • Photo gallery: 2014 Communications Marketing Conference (CMC) in Tucson
  • Elucidations and explorations
    Top 5 Stories - Week of Sept. 22
  • Elucidations and explorations
    RCA plans to expand this year's Technical Symposium

Commentary


Updated: How ‘sidelink’ peer-to-peer communications can enhance public-safety operations

  • 1
27th February 2023

NG911 needed to secure our communities and nation

24th February 2023

How 5G is making cities safer, smarter, and more efficient

26th January 2023
view all

Events


UC Ezines


IWCE 2019 Wrap Up

13th May 2019
view all

Twitter


UrgentComm

How AT&T won DFW Airport’s $10 million private 5G business dlvr.it/Spj4Pt

27th May 2023
UrgentComm

Russia’s war in Ukraine shows cyberattacks can be war crimes dlvr.it/Spj3c2

27th May 2023
UrgentComm

FCC grants 700 MHz Band 14 license renewal to FirstNet Authority dlvr.it/Spj2Ny

27th May 2023
UrgentComm

Broadband for Critical Communications Everywhere Providing Connectivity When Seconds Count dlvr.it/Sph602

26th May 2023
UrgentComm

How vehicle insurance and autonomy intertwined dlvr.it/SpglBb

26th May 2023
UrgentComm

World’s least-expensive self-driving vehicle revealed dlvr.it/Spgc88

26th May 2023
UrgentComm

Voice calling is finally making its way onto 5G dlvr.it/SpdtYW

26th May 2023
UrgentComm

With many cities facing a fiscal cliff as ARPA funding ends, debt ceiling debate continues on Capitol Hill dlvr.it/Spdsnq

26th May 2023

Newsletter

Sign up for UrgentComm’s newsletters to receive regular news and information updates about Communications and Technology.

Expert Commentary

Learn from experts about the latest technology in automation, machine-learning, big data and cybersecurity.

Business Media

Find the latest videos and media from the market leaders.

Media Kit and Advertising

Want to reach our digital and print audiences? Learn more here.

DISCOVER MORE FROM INFORMA TECH

  • American City & County
  • IWCE
  • Light Reading
  • IOT World Today
  • Mission Critical Technologies
  • TU-Auto

WORKING WITH US

  • About Us
  • Contact Us
  • Events
  • Careers

FOLLOW Urgent Comms ON SOCIAL

  • Privacy
  • CCPA: “Do Not Sell My Data”
  • Cookie Policy
  • Terms
Copyright © 2023 Informa PLC. Informa PLC is registered in England and Wales with company number 8860726 whose registered and Head office is 5 Howick Place, London, SW1P 1WG.