Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives Magazine Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Alliance Test Equipment Centric RF Empower RF ISOTEC Reactel RF Connector Technology San Francisco Circuits Anritsu Amplifier Solutions Anatech Electronics Axiom Test Equipment Conduct RF Copper Mountain Technologies Exodus Advanced Communications Innovative Power Products KR Filters LadyBug Technologies Rigol TotalTemp Technologies Werbel Microwave Windfreak Technologies Wireless Telecom Group Withwave Resources Vintage Magazines RF Cafe Software WhoIs entry for RF Cafe.com Thank you for visiting RF Cafe!
Windfreak Technologies Frequency Synthesizers - RF Cafe



Please Support RF Cafe by purchasing my  ridiculously low-priced products, all of which I created.

RF Cascade Workbook for Excel

RF & Electronics Symbols for Visio

RF & Electronics Symbols for Office

RF & Electronics Stencils for Visio

RF Workbench

T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads

These Are Available for Free

Espresso Engineering Workbook™

Smith Chart™ for Excel

KR Electronics (RF Filters) - RF Cafe

Measuring a Transmitter´s output Impedance components - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues - primarily having to spend time purging garbage posts from the board. At some point I might start the RF Cafe Forums again if the phpBB software gets better at filtering spam.

Below are the old forum threads, including responses to the original posts.

-- Amateur Radio
-- Anecdotes, Gripes & Humor
-- Antennas
-- CAE, CAD, & Software
-- Circuits & Components
-- Employment & Interviews
-- Miscellany
-- Swap Shop
-- Systems
-- Test & Measurement
-- Webmaster

Laser
 Post subject: Measuring a Transmitter´s output Impedance components
Posted: Wed Dec 05, 2007 11:14 pm 
 
Lieutenant
User avatar

Joined: Wed Dec 05, 2007 10:09 pm
Posts: 2
Hi everyone.
I was asked to develop a linear amplifier for an RC transmitter (35MHz).
This transmitter uses a simple telescopic antenna, and now I will have to design the amplifier and adapt it´s output to a 50ohm transmission line and antenna.
So far so good, but then, as I started to analyze the problem, things started to complicate a little.
In order to adapt the amplifier´s input to the transmitter´s output, I need to know the transmitter´s output impedance components (resistive and reactive parts).
The resistive part should be something much lower then 50ohm, which is the typical impedance of short whip antennas (antennas bellow resonance).
I also know that short whip antennas present a natural capacitive reactance, and to counteract this, the transmitter has an inductive reactance part on it´s output to balance with the capacitive reactance of the antenna.
This is called Conjugate Matching and in order to adapt my amplifier´s input, I also need to know the magnitude of this inductive reactance.
Now, my question is:
How do I measure these values without using high priced equipment, like network analyzers?
Are there any techniques to do this, with an outside test setup made of variable capacitors, inductors and resistors and then measuring phase shifts, voltages and currents in some way on this setup, with an oscilloscope, that will allow us to calculate the resistive and reactive parts of the transmitter´s output impedance?
My intuition tells me that this is possible, but how?
I´ll appreciate any help.
Thanks


 
   
 
Feng
 Post subject: I gave you my suggestion in Circuit board.
Posted: Thu Dec 06, 2007 4:05 am 
 
Captain
User avatar

Joined: Sun Mar 19, 2006 5:25 pm
Posts: 23
Location: Burnaby
Hi Laser,

I gave you my suggestion in Circuit board where you posted your question first. Hope it is useful.






Posted  11/12/2012
KR Electronics (RF Filters) - RF Cafe
ConductRF Phased Matched RF Cables - RF Cafe

TotalTemp Technologies (Thermal Platforms) - RF Cafe

Exodus Advanced Communications Best in Class RF Amplifier SSPAs