Thank you for visiting RF Cafe! 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 Homepage Thank you for visiting RF Cafe!

MIA: The Other Half of the Antenna and Cable Loss Equation
Kirt's Cogitations™ #288

RF Cafe Calculator Workbook 1-Way RF Path LossFor some inexplicable reason, it seems that most of the articles I read dealing with antenna and feedline efficiencies do not address the receive side of the equation. Yes, transmit power is expensive and there is a legitimate reason to reduce losses when converting power amplifier output to in-the-air power, especially for DX operations. However, it doesn't do much good to launch the full permissible 1,500 watts PEP and make a contact on the other side of the world if your system cannot receive a reply because of the excessive line loss and/or mismatch loss between your antenna and your receiver.

Antennas and feedlines are reciprocal elements so if you allow, say, 12 dB net loss there and compensate with additional transmitter output power, you also lose 12 dB of receive signal power in the other direction. RF energy attenuates at a rate of 6 dB for every doubling of distance, so that 12 dB loss cuts your minimum discernable signal to a source 1/4 the distance compared to a 0 dB net loss.

You can find RF path loss calculators online, or download my RF Cafe Calculator Workbook (MS Excel spreadsheet) and use its "1-Way Path Loss" worksheet. The image above demonstrates the concept using 14 MHz on the 20-meter Ham band - a popular band for DX work.

Transmission Line Types - RF CafeI use window line in my example because it typically has much lower loss than coaxial cable. At 14 MHz, 450 Ω ladder line has a loss of around 0.1 dB per 100 feet, 300 Ω twin lead is about 0.4 dB per 100 feet, and 75 Ω RG-6/U coaxial cable has roughly 1 dB per 100 feet. That's a 10x attenuation factor between ladder line and RG-6/U. Increase your frequency to 144 MHz (2-meter band), and the attenuation factors increase by 4 or more. Coaxial is very convenient to use because its containment of the RF energy within the outer shield makes installation a breeze since routing can be made with reckless abandon (or nearly so). Twin lead and ladder/window line requires more care in routing to avoid the effects of nearby structures. Sometimes coax is the only reasonable choice, but if your goal is to pull in the weakest of stations (due to remote transmit power and/or poor atmospheric conditions), then the lowest loss feedline must be considered.

Hopefully, authors will begin including the receive signal strength in their articles when discussing optimization techniques and rationale.



Posted July 26, 2017

<Previous                     Next>

These original Kirt's Cogitations™ may be reproduced (no more than 5, please) provided proper credit is given to me, Kirt Blattenberger.

Please click here to return to the Table of Contents.

   Cog·i·ta·tion [koj-i-tey'-shun] – noun: Concerted thought or reflection; meditation; contemplation.
   Kirt [kert] – proper noun: RF Cafe webmaster.

These items are an archive of past Topical Smorgasbord items that have appeared on the RF Cafe homepage. In keeping with the "cafe" genre, these tidbits of information are truly a smorgasbord of topics. They all pertain to topics that are related to the general engineering and science theme of RF Cafe. Note: There is also a huge collection of my 'Factoids' (aka 'Kirt's Cogitations') that might interest you as well.

| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 |

RF Cafe Software

   Wireless System Designer - RF Cafe
Wireless System Designer

RF & EE Symbols Word
RF Stencils for Visio
Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel

About RF Cafe

Kirt Blattenberger - RF Cafe WebmasterCopyright
1996 - 2022
Kirt Blattenberger,

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:

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