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 Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering magazine articles Engineering software Engineering smorgasbord RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising RF Cafe Forums Magazine USAF Radr Shop Sponsor RF Cafe RF Electronics Symbols for Visio RF Electronics Symbols for Office Word RF Electronics Stencils for Visio Thank you for visiting RF Cafe!
Windfreak Technologies Frequency Synthesizers - RF Cafe
RF Electronics Shapes, Stencils for Office, Visio by RF Cafe

About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    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 World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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:


Windfreak Technologies SynthHD PRO - RF Cafe

How to Measure Active Antenna'bias voltage from GPS receiver - RF Cafe Forums

RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media platforms dominating public commenting venues. RF Cafe Forums began sometime around August of 2003 and was quite well-attended for many years. By 2010, Facebook and Twitter were overwhelmingly dominating online personal interaction, and RF Cafe Forums activity dropped off precipitously. Regardless, there are still lots of great posts in the archive that ware worth looking at. Below are the old forum threads, including responses to the original posts.

-- Amateur Radio

-- Antennas

-- CAE, CAD, & Software

-- Circuits & Components

-- Employment & Interviews

-- Systems

-- Test & Measurement

 Post subject: How to Measure Active Antenna'bias voltage from GPS receiver
Posted: Thu Apr 19, 2012 12:32 pm 

Joined: Thu Apr 19, 2012 10:44 am

Posts: 2

Dear all,

A dummy question.

I've got a GPS receiver chip. This chip has a [+3,+5]VDC voltage bias for active antenna.

I wonder if it is possible to measure the presence of the voltage bias on RF port ?

The aim is to validate that the voltage is compliant with the LNA inside my active Antenna.

Basically, I though to directly connect the voltmeter on the central conductor of SMA port. Is it good ? Or is there a problem of mismatch ?

Best regards and thank you by advance.

Kirt Blattenberger
 Post subject: Re: How to Measure Active Antenna'bias voltage from GPS rece
Posted: Fri Apr 20, 2012 7:49 am 
Site Admin
User avatar

Joined: Sun Aug 03, 2003 2:02 pm

Posts: 476

Location: Erie, PA

Greetings florent:

The receiver input is almost certainly tolerant of any RF impedance as long as you are not worried about RF performance during the measurement, which you are not. If you can find the datasheet for the GPS IC, it will probably contain a warning about shorting the Rx input if it is a problem. The DC impedance of any modern DMM is extremely high (>1 MOhm), so you should have no problem making the voltage measurement. If you are still leery of placing the probe on the input, wrap the lead around your finger a few times to add a little inductance to the probe line as an RF choke.


- Kirt Blattenberger :smt024

RF Cafe Progenitor & Webmaster

 Post subject: Re: How to Measure Active Antenna'bias voltage from GPS rece
Posted: Mon Apr 23, 2012 7:14 am 

Joined: Thu Apr 19, 2012 10:44 am

Posts: 2

Dear Kirt,

Thank you very much for your answer.

I've performed the DC measurement : 3,25VDC which is the order of magnitude that I saw on various datasheet.

In fact, I haven't the reference of the receiver. Let me explain : I'm working on an analysis concerning GPS signal default. The GPS receiver chip is included inside an embedded computer. I've contacted the manufacturer to get the name of the GPS receiver but without succeed.

That is the reason why, I would just perform a first check of the DC bias voltage. I hope to get the datasheet from the manufacturer.

In all case, I thank you again for your support.

Your forum and web site is a great source for young dummy engineer like me.

Best regards,

Posted  11/12/2012

DC-70 GHz RF Cables - RF Cafe

RF Cafe Visitor Comments on News, Articles, System, Design, Components, etc.

Please e-mail your comment to me (Kirt B.), and I will post it here for you - no computers involved!

1 - Your participation will be greatly appreciated. - Kirt B.

PCB Directory (Manufacturers)
Amplifier Solutions Corporation (ASC) - RF Cafe

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

These Are Available for Free