RF Amp and antenna input circuit

The input should be matched to the antenna and the amp input. I will use a bandpass filter for 80 meters. First the page from the book.

and the results.

The sweep.

Needs a Local Oscillator and some bandpass filtering

The direct conversion unit can cover any portion of the HF spectrum by simply tuning the LO as desired. Some filtering may be required to keep the signal clean. I am in the fringe area of the two closest AM stations so not much concern about that. Anywho the next step is the LO. We could keep it simple and just build a Lamda Diode oscillatoe or be a little more adventerist and buils an oscillator with Vcap and coils? We need to look at stage interaction. It is easy to build a single stage and get good gain. Not so easy when we tie stages together and they interact. It seemed some folks would see a new schematic and start declaring this that and the other were not needed. Maybe we could try removing a part here and there to see what happens but most every piece of this set has a purpose.

The radio less the LO

Now we apply the signals across a non linear device and see a much different output. The readout measure a signal of 1Khz. How does a 1000khz and 1001khz produce a 1khz outout. The non linear action of the diode procuces 4 output posibilities. They are the sum, difference, and 2 orignials signals.

In this circuit I simply apply 2 signals to a resistor and the produce an algebraic sum or difference of their amplitudes. The resistor being a linear device it has no effect on the signal phase or frequency.

Years ago my friend Andy built the 40/80. It is a good example of the dual conversion as presented in the block diagram. What I have in mind this time is a JFET design rather than the MOSFET. I bought a box of K2539's for $5 and I tend to use them first. I also have some J112 and J175 to try. My design tool of choice is LTspiceIV. Other tools may give good results but LTspice is an old friend. The next contender is QUCS "Quite Unerversal Circuit Simulator". I have used QUCS just enough to see the possibilty. It is available is several packages for Linux, Windows and Mac. Now things to consider: Should I use a DBM or active detector? Single conversion or dual conversion? Thrown together with a minimum of parts. etc.... look at the 40/80 here: ***** https://radio.radiotrician.org/2018/11/dbm-and-dual-gate-mixer.html***** It uses a DBM and dual gate mxer. DBM maybe but no dual gates this time.

10/10/25 ready to start a new receiver.

I am thinking a JFET direct conversion receiver. it will consist of : RF Amp Mixer AF Amp LO Osc *I will probable use a 2n3904 for the AF output. Building a single stage is not to hard, the troubles start when feeding other stages. We will be looking at loses due to Z mismatching and shared power supplies. I will use LTspiceIV for the sim's. (more on this later) I reloaded my old HP desktok with a new OS and the tools for the project. (more on this as we proceed - I may use a couple of other tools?)