EMRFD Message Archive 10991

Message Date From Subject
10991 2015-04-23 12:30:53 cwfingertalker Noise Blanker circuits

Hello to the Group,

I am just about done fussing with my Progressive Receiver and ready to button it up, decal it and put it on the operating bench from the work bench.  My reciever runs from 3.0 to 4.0 mhz with a 9 mhz IF.  I just finished building an S meter circuit for it that works very well.  My next project will be to build an outboard converter for more few choice bands.  

I noticed while listening around on 80 and 75 meters that the electric fences in my rural neighborhood can be quite loud at times.  I looked at an old schematic in the 1981 to mid 90's Handbook and there is a rather simple noise blanker circuit using about four devices.  One of the transistors is a dual mosfet (40673) that could be substituted with an SMT device or re-engineeried with a regular FET.  

I was wondering if anyone here has a favorite noise blanker circuit.  Something that could work on electric fence noise and simple enought to build manhattan style.  

Bill N7EU

10993 2015-04-24 02:16:31 Kirk Kleinschmidt Re: Noise Blanker circuits
I've always had the best luck using a well-insulated wire cutter to handle electric fence noise.

Snip. Reapply "blanking" as necessary.

I think the MFJ model number is MFJ-1027 -- optional pouch is extra.


Ooops. That was just a daydream...

What wasn't a daydream was using said wire cutter back in the day to cut electric fence wires that errant farmers had strung (illegally in MN) across canoe-navigable waters. You only got one chance to grab the wire with the insulated mega-cutter before it grabbed you!


--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)

10994 2015-04-24 05:52:23 k1rf_digital_stev... Re: Noise Blanker circuits
You can try this simple audio noise blanker from Chris Trask:
-Audio Noise Blanker 01

Or a more effective but complex impulse noise blanker also from Chris Trask:  http://home.earthlink.net/~christrask/Noise%20Blanker.pdf

"Digital Steve" K1RF


10995 2015-04-24 09:20:24 cwfingertalker Re: Noise Blanker circuits

Thanks for the lead on the web.  I just might try the audio limiter first.  I have seen some simple circuits for that before.  I also would like to try a simple IF blanker.  I just have to read up on the theory and see if it is feasible.  

Bill N7EU
10997 2015-04-24 10:29:47 joe blow Re: Noise Blanker circuits
Use the Heathkit blanker that is used in the SB104.

10998 2015-04-24 11:47:41 Chris Trask Re: Noise Blanker circuits
> I was wondering if anyone here has a favorite noise blanker circuit. Something that
>could work on electric fence noise and simple enought to build manhattan style.

This online paper of mine:


may be a bit more involved than you're interested in, but in it I explain why you need to blank out those noise impulses very early.

Chris Trask
Senior Member IEEE
10999 2015-04-24 12:11:09 Clint Re: Noise Blanker circuits
As a side subject,  I have a couple of modules that use a simple circuit that simulates ignition noise.  Very handy for adjusting the threshold on noise blankers in a radio.
11000 2015-04-24 13:17:13 w7zoi Re: Noise Blanker circuits
Hi Bill, and gang,

Another excellent noise blanker paper is that presented by John Stephenson, KD6OZH (sk.)   This was part of his ATR-2000 transceiver which appeared in three parts in QEX March 2000, May 2000, and March 2001.   The noise blanker appears in the May 2000 issue.    The emphasis in his design is to provide a noise blanking function while not compromising the receiver IMD performance.    This is the general circuitry used by Markus, VE7CA, in his transceiver.

Plow through the literature and I'm sure you will find a lot of good stuff on noise blankers.   Good luck.

73, Wes

11002 2015-04-24 18:33:56 William Martin Re: Noise Blanker circuits

Thanks for the tip.  I downloaded the article and I will study it.  

Bill N7EU

  William Martin's MacBook  

11003 2015-04-24 18:54:31 William Martin Re: Noise Blanker circuits

Thanks for the lead.  I bookmarked the VE7CA website for further study.  They QEX articles don't seem to be available to me on the ARRL website.  No problem.  I have plenty to look over.  

My original idea came from the July 1971 QST article by Frank Van Zant W2EGH.  This is the IF Blanker featured in the Handbooks for many years.  I was thinking of starting at that point and see how complicated this project would get.  

73 Bill N7EU

  William Martin's MacBook  