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 Forums RF Cafe Homepage Thank you for visiting RF Cafe!

Help! Need Some Advice on Cable Compensators... - 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

Post subject: Help! need some advice on cable compensators... Posted: Thu Nov 24, 2005 10:01 am


Joined: Thu Nov 24, 2005 2:40 am
Posts: 3
Hey guys,

I am in a quandry (Am trying to increase my vocabulary, and this is one of the new words I learned). I need to make a cable compensator. I have a basic idea of how the full device should work, but I am not sure how the cricuit works exactly. The biggest problem (from what I have read) with the compensator I need is that it needs a bandwidth of just over 1 Ghz. If anyone can offer some advice, or direction to a website it would be greatly appreciated!




Post subject: compensatorPosted: Thu Nov 24, 2005 11:27 am
When dealing with compensators, there are several questions you need to answer:
1. Fixed compensation, (manually) adjustable compensation, or automatic (self-tuning) compensation. These somewhat depend on whether the conditions you're compensating for are going to change either significantly or rapidly.
2. Assuming it's gain flatness and constant group delay you need, what is the range of correction needed? (Example: cable is down 20 dB at 1 GHz)
3. How accurate does it need to be (1 dB? 0.1 dB? 1 nanosecond? 100 picoseconds?)
4. Active or passive?

Good Luck!


Post subject: Posted: Fri Nov 25, 2005 5:02 am


Joined: Thu Nov 24, 2005 2:40 am
Posts: 3
hey mystery guest,

The questions were actually very useful (read:I hadn't thought of all that!). The compensator is meant to work on a very long coax line (about 60m if I am not mistaken). Delay not really the issue, but gain flatness is a BIG issue, I would like it to have as high an accuracy as possible (It is on our radio telescope, so we are doing VERY low level noise measurement). Also, the cable isn't really gonna change at all, so it will need to be adjustable, but just once so that you can set it for the specific cable and forget about it. Also, Passive I think is the way to go!

I have the old unit here on my bench, and just tell me if I am completely wrong in my assumption. It looks like a butterworth filter, of which the Q is adjustable (with a little pot). I can't imagine that it would work at a particularly high frequecy as they have used old 5% carbon resistors... So what I would like to try is to replace it with is an adjustable Q tuned circuit, and use the lower end of the frequency responce slope as the compensation curve... Have I got the wrong end of the stick, or am I on the right track?

Thanx a lot for the help so far!



Post subject: EQPosted: Mon Nov 28, 2005 11:55 am
Do you really need that much correction for the gain? The unit you have is one of the classic configurations - a LPF with adjustable Q.

You might want to try to measure the response you're trying to equalize, and then using optimization to get the values for an equalizer. Tom Cuthbert's books discuss this in detail. (

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
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 !