I wanted to build a radio receiver designed by N1TEV for a long time. Thanks to my friend Henrik ( DK8HM ) for the PCB he sent me to build this receiver.
I always avoided this N1TEV design because it needed two variable capacitors. These days they are not easy to find. I think I may have a solution for that, in a future video when I will come back with another version of this regenerative receiver. Here you have the tests and the initial build. I’m still trying to get used to the regeneration control, as it’s not as easy to use as it is on the Sputnik Regenerative Receiver.
It sounds really nice and has good sensitivity. Maybe a little too much sometimes, as I have to use it with the RF attenuator at 40% in order to have a good modulation for the amateur radio signals. A lot of fun building it though. Special thanks to my buddy Hendrik in Germany ( DK8HM ) who sent me to test the PCB board he designed.
THE SCHEMATIC
The schematic of the radio receiver designed by N1TEV usually includes an LM386 audio amplifier. In this case that was left out. The idea is that everyone can pick the audio amplifier they like. Some people prefer the simple LM386 audio amplifier, others may chose a transistors based audio amplifier. Lately I’ve been playing with a TDA2003 audio amplifier and it sounds way better than the LM386.
The schematic is really simple, but if you asked me twenty years ago, I may had a different opinion. I never had the possibility to measure the variable capacitors I had. Another issue was that I didn’t used the proper JFET and for that reason in the past, this receiver never worked for me. But… it works now, twenty years later.
Original Image Source tuberadio.com
BUILDING THE RECEIVER
Most versions of this receiver I found online, were built Manhattan style. I wanted to do the same, until I received the PCB board as a present from Hendrik. So I decided to put it to use and build my test shortwave receiver design by N1TEV. I think the only thing harder to make was the coil. In my case I had four coils instead of the original design. The reason behind that, was that I had an extra coil used for the frequency counter. It did got me a little confused when I had to solder the coil and I had no clue what wire went where.
I built the coil on PVC pipe with the diameter of 31mm. For a receiver that performs well, use good quality components. C3 especially has to be an NPO capacitor for a good frequency stability. For the JFET transistor you can use either an MPF102, or a J110. I used MPF102 thanks to my buddy Nigel who sent me a few.
I forgot to mention in the video, but with the last adjustments, I managed to cover from 3MHz up to 7.4MHz. The only thing I changed from the coil was to use 20 turns instead of 18 or 22 as it seems to have in most schematics online. The variable capacitor used for main tuning, was around 60pF if I remember well.
SENSITIVITY
If you watch the video above, you will hear me saying that the receiver is overloaded with signals. Later on I realized that the receiver was not actually designed to be used with a proper 40m band EFHW antenna. A piece of long wire would be ok. In my case I had to set the RF attenuator really low not to overload the receiver with signals. If you build it for one of the amateur bands, this receiver works absolutely amazing.
Using it for general shortwave coverage is also great and it sounds really nice too. What I did noticed, is that the stability in frequency was not as great as I was expecting it comparing it to other receivers I built. I believe that it can be fixed and make it more stable in the future. As far as I’m concerned, I find the designs by N1TEV to be one of the best shortwave regenerative receivers I found online. If you want to learn and change the frequency of the receiver, down below you will discover the easiest way for me to do that.
When I started playing around with receivers schematics, I did not know how to calculate the circuits to resonate on the frequencies I wanted. I learned the hard way and at first I discovered how to do it by trial on error. Later I discovered that using some really simple online calculators, can save me a lot of time and also enameled copper wire.
CONCLUSION
Unfortunately I do not have a PCB design prepared for you to download and make using the toner transfer method as I usually have. Is because the PCB I received was a present and I didn’t had to work on one. I want to test a few more things and make a few changes to the schematic first. But I will come back with another video and article based on this regenerative receiver design in the future. I have a good feeling that this can become a really great receiver, both for amateur radio bands, or for general shortwave coverage. Right now I am using this particular receiver for my entertainment, for the shortwave broadcast bands mostly.
73 DE YO6DXE