The following is written by Rick, W7RNB / WI2XJQ, and reproduced here with permission:
I won’t lay claim to knowing all the in’s and out’s of how this little jewel works but I will say that is works very well. And I am more than happy to tell you that Mr. BOPP really did himself proud. I have been looking for a circuit such as this for awhile now because I live in a noisy environment, where you can go all day looking for the problems and never really settle anything. Its just that way. So this circuit has helped to get my noise to a decent level.
So, lets get right to it –
First, look up the X-phaser, By Mathias Bopp on the web. Easy to find and all of the details are there on how to build it. I made some minor changes because my junk box just didn’t have exactly what he called out but the results are the same – “ It Works”
The one and only issue that I had was that the toroid he used was a ft-50-77 and since I didn’t have one I found an old EMI toroid that the I could put comparable winding onto that would give me the same results.
My toroid – what I did was to figure out the uh of the primary and then those of the secondary. Calculated how many turns it would take to match those numbers with my junk box toroid and wound it up. It works great.
The last but really insignificant change is that Mr. Bopp called for 56pf in the phase circuit. I used 62pf silver mica capacitors.
In the circuit –
I didn’t have a 1mh choke so I substituted a 8.9mh choke
The two 240 ohm resistors were substituted with a 120 ½ watt resistor.
In the power lead the 1nf and the 100uf were deleted and a 20uf 35Vdc Electrolytic was used.
The relay was not used because I run split on 630 meters and have a relay in the RX line that takes all the receiver circuits to 50 ohms during transmit periods.
The only other thing I did was to use small PC board components that would allow me to mount everything ‘Dead Bug Style “ and eliminate all of the extra wires, that could possibly allow extra coupling throughout the circuity.
Here is a picture of the finished unit as I am using it now, before I install the case. Testing continues but I think it is a keeper.
Here is a picture of my circuit board – Point to point – dead bug style –
I live near a broadcast station at 620Khz, I use a pretty good low pass filter but during the day it still comes through. With this circuit board tuned properly I can copy Larry WH2XGP all day long and the AM broadcast noise has no affect. It is quite simple to tune up and easy to use. I hope you enjoy it as much as I do.
Mathias Bopp, Engineer –
GL – Rick W7RNB / WI2XJQ