Electronics World Cover,TOC,and list of posted Popular Electronics articles QST Radio & TV News Radio-Craft Radio-Electronics Short Wave Craft Wireless World About RF Cafe RF Cafe Homepage RF Cafe in Morse Code Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs Twitter LinkedIn Crosswords Engineering Humor Kirt's Cogitations Engineering Event Calendar RF Engineering Quizzes AN/MPN-14 Radar 5CCG Notable Quotes App Notes Calculators Education Magazines Software,T-Shirts,Coffee Mugs Articles - submitted by RF Cafe visitors Simulators Technical Writings RF Cafe Archives Test Notes Wireless System Designer RF Stencils for Visio Shapes for Word Search RF Cafe Sitemap Advertising Facebook RF Cafe Forums Thank you for visiting RF Cafe!

RF Propagation - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement


Mr.Whatever
 Post subject: RF propagation
Posted: Mon Apr 10, 2006 9:51 am 
 
Captain
User avatar

Joined: Fri Apr 07, 2006 6:10 pm
Posts: 18
Hello,

Does this seem logical?

1. The signal strength (example in dBm or mW) from a transmitting source is measured.
2. Assuming most of the attenuation is due to free space loss, the free space loss factor is "added" back to the measured signal to get the ERP of that specific radiation lobe (it could be main, side, or back lobe).
3. The transmitter output is a known value (example 2 Watts).
4. Using the calculated ERP for a specific lobe, I can use the following to determine the loss / gain due to the antenna & cable: loss/gain = 10 log (transmitter output / ERP specific lobe).
5. If I rotate the transmitting antenna to 360 degrees, then I should be able to have a rough picture of its azimuthal radiation pattern at a certain elevation angle.

I'm probably using the terms the wrong way because I think ERP is synonymous to the main lobe of the antenna (right?). But I'm just treating the ERP as specified only to a certain lobe without knowing if its the main, side, or back lobe.

I'm really not sure if this is right. I just want a confirmation whether my logic is wrong, and if so, why? Thanks!


:?


 
   
 
fred47
 Post subject: Antenna pattern measurement
Posted: Mon Apr 10, 2006 8:02 pm 
 
General
User avatar

Joined: Wed Feb 22, 2006 3:51 pm
Posts: 104
Hi!

Don't forget about the gain of your receive antenna, and about possible reflections (the bane of antenna measurements!). Reflections from the ground are particularly problematic with certain antenna designs. Reflections from nearby structures are often also a big problem. Remember, it doesn't have to be shiny or even reflective at light frequencies to be a jim-dandy reflector at RF.

Remember that the effective area of the antennas is intimately connected to the gain. The transmitted power is spread out over an area, and your receive antenna gathers power over an area. That's the origin of the inverse-square law.

Rotating a transmitting antenna through 360 degrees is a standard way of making antenna pattern measurements.

Good Luck!



Posted  11/12/2012

RF Cafe Software

   Wireless System Designer - RF Cafe
Wireless System Designer

RF & EE Symbols Word
RF Stencils for Visio
Calculator Workbook
RF Workbench
Smith Chartâ„¢ for Visio
Smith Chartâ„¢ for Excel

About RF Cafe

Kirt Blattenberger - RF Cafe WebmasterCopyright
1996 - 2022
Webmaster:
Kirt Blattenberger,
 BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:
 AirplanesAndRockets.com

Try Using SEARCH
to Find What You Need. 
There are 1,000s of Pages Indexed on RF Cafe !

height-line