Noise Cancellation Part 3

Those local noise sources are a real problem to the serious shortwave listener or amateur operator. Here is a simple Noise Canceller design that is a good first attempt. It's doing a good job at from at least 2-20 MHz with my 10 ft noise antenna.

[@nigelbrockwell6237]

Most impressed how well your unit is working so far and with fewer components than the one I built a couple of years ago. I will continue watching this project as you proceed through its future stages. Noise cancelling really works, would be lost without it now.

[@benthere8051]

You could use a 365 pF variable capacitor in your phase shifter in place of the 50 pF fixed which would make it suitable for low frequencies and high frequencies. I like your construction technique with the "islands' on FR-4. I wonder if there's a market for 1/4" punched-out pieces of FR-4 for prototyping. I have used areas on my production 0.031" Teflon PCBs as etched capacitors and inductors in the past. Their thermal stability was acceptable for many applications.

[@MIKROWAVE1]

There are several things that could be done to improve the phase shift circuit. I saw one approach that uses a balanced approach and variable capacitors. The simple All Pass used here is the most basic that I could find.

[@mauldulated302]

I have been meaning to build a noise cancel box for years. Now that i live in the city, and after following your videos. I will take inspiration and build one!

[@spyrosliolis6761]

Just 4 words for you: You are a scientist!!!

[@W1RMD]

Thanks for sharing this excellent circuit with us.

[@acestudioscouk-Ace-G0ACE]

The results look impressive, thanks for your work in developing and filming. I'm looking at my junk box, to see which parts I have and which I need to buy it. Best 73.

[@sincerelyyours7538]

That circuit seems to work nicely! I wonder if a few clamp-on ferrites on the power cord going into the circuit might improve things as well. I've had some success using those on the wall worts feeding my 70s era Sony AM/FM/Cassette deck and my SDR Play box. Turning off the LED lights in my lab helped as well, but there's still lots of room for improvement. I'm looking forward to the soup-to-nuts version of your circuit so I can start purchasing build parts.

[@madmax2069]

I bought one of those $60 QRM Eliminators on Amazon, I've had pretty good success with it. Like you said and I figured out you'll fail or succeed just by the Aux/Noise antenna choice and where you place it, and how you place it. I posted a lengthier post, but KZbin kept nuking it.

[@phildurall7466]

Nice coverage .... As a kid, I though of this approach to deal with noise. You just made such a dramatic display of how well it can work! Thank you! I look forward to the following sessions. 73 - KF6IF

[@Homer19521]

Success or failure. Too many hams fail to realize that every QTH is different & the biggest variable is the operator. I have 3 different QRM NC's. I bought a MFJ1026 for $20 at a swap. Wouldn't power up & found a blown inductor on the PS side. Replaced it & viola! Works quite well. The TW ANC4+ has a good S unit or 2 signal loss when in circuit. Disappointing. I have a 3rd unit, an ebay special that I have yet to really assess. Thanx for the vid. 73

[@Steve-GM0HUU]

Thanks Mike and looking forward to next episode. Even this basic circuit can obviously be very effective. As if by magic, the noise is gone. One thing I was curious about is if adding an antenna "tuner" to the noise antenna to get a better match at operating frequency would make any difference.

[@MIKROWAVE1]

As I dress down the components, use short coax sections rather than long wires, and have swapped to a Magic Tee combiner, I am reaching the limit of my test gear getting beyond 50 dB of rejection from around 5 MHz to 30 MHz. But markedly less performance at 75M with 35 dB and only 10 dB in the BCB. Still significant improvement, but it is apparent that Type 75 material would be a better choice at LF and MF.

[@robertvandersanden]

You can always try to stack 2 ferrite cores of different mixes on top of each other and wind on that combi to get a good performance over a wider range. And when looking at the gain stage, I would place the gain pot in the drain of the JFET instead of the resistor and go from the wiper into the next stage. That way the output remains 50 ohm.

[@grs6262]

my noise in this QTH is pretty near catastrophic---the MFJ1026 added to the line up is the only thing that has made listening possible again--it has allowed me to hear signals on 20 meters once more during the day, and has rid 40 meters of most of the hash--i need to devise a better noise antenna--but a 6X8 foot balcony limits one

[@alainmichaud8992]

I like tat video. Thank-you.

[@clytle374]

That is amazing. I guess the part I missed out on when disbelieving this was possible was realizing the the second antenna needed to receive the noise and not the signal, so there was a difference to remove. I asked earlier if it would remove static crashes from lightning, the plague of 80M. So I'm thinking it would help for local lightening if I put up a vertical noise antenna in addition to my 80M horizontal delta loop, an antenna I picked as I was told it has lower noise. An additional thing I think I have noticed is that remote lightning seems to often not be much of an issue until the person transmitting is near it. Does the lightning mix with the signal, or am I imagining this? Anyway back to the Heathkit Hw-101 VFO that I'm rebuilding on the bench, a problem there will make your life miserable.

[@gretalaube91]

You know, that separate RX antenna pass-through on the back of my old IC751a could benefit from a noise antenna and box.... I wonder if the impulse response of the all-pass and buffer/amp would mess up the null somewhat? OH, just read your comment below. Nope. OK, heating up the soldering iron..... TNX Mike es 73 de W3IHM

[@W4BIN]

I always found 2N2222A's to be rather nosier than later designs, a 2N3904 would probably be a better choice, that noise probably would not be tunable out. Otherwise nice. Ron W4BIN

[@misterhat5823]

The 2N3904 is pretty darn quiet for a GP BJT.

[@wesKEVQJ]

If I want to listen to station A, which is on the same frequency as station B but a is further away and B is in between, can I use this to caancel station B? If I use a high gain antenna and a low one?

[@kerzman]

So, is physically moving around my AN200 loop antenna (MW) to find the least noise just adjusting the phase?

[@MIKROWAVE1]

Not unless it has another antenna as a reference to phase against. Otherwise you are just nulling the noise source line of bearing.

[@JCWise-sf9ww]

Can this device be adapted for LongWave and Standard Broadcast AM bands?

[@MIKROWAVE1]

Ha yes that is certainly the worst of the worst for many folks. The answer is yes, and it is actually where the basic noise cancelling work started back in the early days.

[@JCWise-sf9ww]

@@MIKROWAVE1 The toroid transformer and the number of turns shown, have the bandwidth to handle frequencies from 100kHz through 2mHz efficiently? or do we have to use more turns of wire?

[@MIKROWAVE1]

@@JCWise-sf9ww You start to see degradation below 6 MHz. type # 75 or 77 are preferred rather than adding turns to the #43 where you want to be. I also tried a binocular #43 and it did improve the low end of the BCB. The next video covers this.

[@JCWise-sf9ww]

@@MIKROWAVE1 Ok

[@K1OIK]

I have arcing on a pole; it would be easier to cut down the pole than build this

[@K1OIK]

You can't use it with a transceiver.

[@Steve-GM0HUU]

Yes, I was thinking that I might try to build one of these. However, as I would want to use it with a transciever, some kind bypass solution would be needed for transmit.

[@K1OIK]

@@Steve-GM0HUU What a genius, how did you ever figure that out?

[@Steve-GM0HUU]

@@K1OIK I simply imagined the noise reducer output poing pop trying to dissapate 100W RF.

[@gretalaube91]

My Icom 751a has two jacks on the back panel where the RX RF passes through after the relay. I will just add the noise box and noise antenna there, no fears. Check your XCVR?

[@Steve-GM0HUU]

​@@gretalaube91 Thanks. Although some rigs have an RX antenna socket, it may not be help with this noise canceller. The combiner needs an input from the noise antenna and the normal antenna.