If you're a ham struggling to pick out signals with an S7 background, one of these may be your answer. The noise source is received on a separate antenna, inverted, and subtracted from the primary signal. And it is a great kit to build!
This is version 3.40. Still the same basic circuit as version 3.0. Cleaned up the silkscreen and added a trimpot to allow the adjustment of the time delay for those who use CW. I have built and tested a few kits for those who, for whatever reason dont want to take on the task of building the kit.Watch my other listings if you're interested in an assembled unit. Background Most hams have at some time or another had to deal with interference from nearby TVs, LED lamps, power lines, computers, solar panels, etc. A common theme to get rid of this QRM (popular since the days of vacuum tube TVs) is to use a second noise antenna used to collect a suitable sample of the noise, invert that signal and add it back to the main signal. It is very dependent on the shape and location of this noise antenna. The good news is that they can be reasonably effective. Dont expect miracles but one of these can get rid of enough noise to make them well worth having. They can do a great job of canceling nearby man-made noise from plasma TVs, solar panel inverters, powerline insulators, furnace motors, a nearby radio station, etc. They really dont do much to cancel atmospheric noise, even though number of people have responded that even the general background noise is down by nearly an S unit. (I still suspect that is probably a reduction in some unidentified local noise source).
This is similar in design to the commercial versions, including the MFJ-1026, and ANC-4, and the X-phase from Russia. They all work more or less the same way.The X-Phase is very basic but functional, the MFJ has a nice pre-amp on the front end. If you are lucky enough to live faraway from civilization and dont have a local noise problem, one of these is not going to do much for you. It doesnt matter the brand. On the other hand, you may be dealing with a local noise source and not realize it until you try this method to get rid of it. This unit is well built in a nice heavy, aluminum shielded enclosure and manages to fix some of the shortcomings of the other units (my opinion).
For example, the LNA for the front end was really needed, it gets the noise channel up to a manageable level to be inverted without distortion. And the 2N5109 buffer added just enough gain so as to minimize the knob tweaking to kill the noise. Aside from that, the circuit is much like the others.Two J310 FETs act to buffer and combine the two basic signals, one of the signals being inverted by the phase-shifter following transformer T1 (see schematic). The combined signal is then buffered by Q4 and sent to the receiver through a relay. In transmit mode, the relays serve to isolate the QRM device and allow the transceiver to be connected directly to its antenna. That bypass relay is a bit heavier than the others, comfortable to over 200W. There is also circuitry to detect the RF and use the relay to protect the amplifiers (same as most of the commercial units).
That circuit works but it is not foolproof, especially on SSB so you should rely upon the PTT or other signal from your transceiver for control. This is true for any of the available units.
You will need to provide a PTT cable from your transceiver. You must have some sort of antenna to receive the noise signal. There is a lot of advice on the subject, but in the end you just have to experiment. A wire on the shack floor might get some improvement, but it is probably going to be minimal.
This kit includes a decent amplifier (30+dB gain) for the input of the noise antenna but it will still likely take a small outdoor (or attic) antenna to effectively receive and cancel the noise. Depending on the noise type and location, an old 2m antenna can work very well. Did I mention that all of the components are nice large through hole types? I have tried to price it fairly, this is not a business, I'm just an old fart enjoying ham radio, but I do want to try and break even on the project. If I can, my wife will let me keep playing.I have a limited number of assembled units but I will occasionally build more as time allows. It will take a little time (probably 4 or 5 hours), but it is not overly difficult and you will gain some experience. Be aware however, that I will not be able to support you with replacement parts if needed. It is simply too expensive and difficult to send international from the US. The item "NOISE CANCELING QRM REDUCER KIT! ELIMINATOR PHASE INVERTER, Quick US ship" is in sale since Wednesday, March 18, 2020. This item is in the category "Consumer Electronics\Radio Communication\Antennas\Ham, Amateur Radio Antennas". The seller is "iroriqm" and is located in Ramona, California. This item can be shipped to United States, Canada, United Kingdom, China, Mexico, Germany, Japan, Brazil, France, Australia, Russian federation, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Greece, Portugal, Cyprus, Slovenia, Sweden, South Korea, Indonesia, Taiwan, Thailand, Belgium, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Austria, Bahamas, Israel, New Zealand, Philippines, Singapore, Switzerland, Norway, Saudi arabia, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Chile, Costa rica, Dominican republic, Panama, Trinidad and tobago, Guatemala, El salvador, Honduras, Jamaica, Antigua and barbuda, Aruba, Belize, Dominica, Grenada, Saint kitts and nevis, Saint lucia, Montserrat, Turks and caicos islands, Bangladesh, Bermuda, Brunei darussalam, Bolivia, Ecuador, Egypt, French guiana, Guernsey, Gibraltar, Guadeloupe, Iceland, Jersey, Jordan, Cambodia, Liechtenstein, Luxembourg, Monaco, Macao, Martinique, Maldives, Nicaragua, Peru, Pakistan, Paraguay, Reunion, Viet nam, Uruguay.