Z matching vs neutralizing

3 stage amp with filter and feedback

This little 3 stage amp works really well in sim. R4 and R5 form a voltage divider for the degenerative feedback. They could be replaced with a pot or rheostat for volumn control. C4 could feed a transformer to feed a low Z speaker or headset. The input PI network is a low passs filter which should keep RF out of the amp.

The old world way of doing it. Based on the formulas posted earlier.

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.

The radio less the LO

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.

Bandspread vs range continued from previous post

If you observed the effects of adjusting the Vcap ratio by adjusting the low end capacitance and the high end by adjusting the "trimmer" It should be easy to understand the importance of making the adjustments in order. The 600KC adjustment sets the bandwith while centering the range over the correct dial point. The 1400KC adjustment sets the high scale to the correct point. You must work between the two to get the proper operation of the set. Both effect both ends of the scale so the 1400KC could be adjusted without first setting the 600KC and then you are looping back and forth with to wide a band. You can set the dial to 1400KC and adjust either one adding the low range adjustment while reducing the high range adjustment and hold the output steady. Anywho here are a couple of excert from the service manual.

The alignment procedure on one sheet.