This is a slightly upgraded version from version 3.1 The connectors have changed a little and it now includes a 9V supply for the LNA. It is still the same basic circuit design. It did cut the cost by a little. The kit includes good quality PCBs with silkscreen, ground planes, plated thru holes, and epoxy solder mask both sides.It includes all the board components all full size parts, no surface mount! Two PCBs, a low noise amplifier with SMA connectors, and step-by-stepish instructions. A heavy aluminum enclosure, a nice front panel, pre-drilled rear panel, connectors, knobs, and power supply. You provide a little solder and the labor. Its a fun kit to build with just a few common hand tools. This maybe isn't for a complete novice but if you can solder and know what a resistor looks like you shouldn't have any problems. There are a lot of parts, so give yourself a couple of evenings to complete the project. If you are not sure what this does, check Youtube, search for QRM-180 there are several users that have posted video using this or some similar units.
Background Most hams have at some time or another had to deal with interference from nearby TVs, LED lamps, power lines, computers, solar panels, nearby radio stations, 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. 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 but they really dont do much to cancel atmospheric noise, still a number of people have responded that even the general background noise is down by nearly an S unit. (I suspect that is still 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, the ANC-4 is very well made although a bit tricky if you have to work on it.
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).
The LNA for the front end was added to get 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. There are also filters and fuses on all the inputs. 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 some 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.
And 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 really 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.
As-is, the QRM-180 works well on 160-10M. Tom WB4JWM has had considerable success on 630M with some modifications. Let me know if you are interested in this band and I can configure the kit with his suggestions. One QRM-180 unit, not assembled.(boards, components, case, knobs, front/rear panels, connectors). I provide decent step-by-step instructions, but certainly not a professional manual. You will need tolerable soldering skills, hand tools, and at least a cheap volt/ohm meter to check component values (if your eyes are as bad as mine). 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, look for my other listings. The item "NOISE CANCELING KIT QRM REDUCER ELIMINATOR PHASE INVERTER, HAM RADIO Quik US ship" is in sale since Wednesday, March 6, 2019.
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, Denmark, Romania, Slovakia, Bulgaria, Czech republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, China, Sweden, South Korea, Indonesia, Taiwan, South africa, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Israel, Mexico, New Zealand, Philippines, Singapore, Switzerland, Norway, Saudi arabia, Ukraine, United arab emirates, Qatar, Kuwait, Bahrain, Croatia, Brazil, Chile, Colombia, Costa rica, Dominican republic, Panama, Trinidad and tobago, Guatemala, El salvador, Honduras, Jamaica, Viet nam, Uruguay, Aruba, Dominica, Grenada, Saint kitts and nevis, Montserrat, Barbados, Bolivia, Ecuador, Guadeloupe, Iceland, Jordan, Luxembourg, Martinique, Nicaragua, Oman, Peru, Paraguay.