Regarding Circuit Boards for the
Hybrid Cascode General Purpose AGC IF Amplifier
w7zoi & wa7mlh, QST, December, 2007 pp 30-33.

(11Nov to 12Dec07, 2Jan08, 7April13, 26may13)    

Click here for errata.  (latest 3Dec07)
Click here for applications information (Modifications, S-Meter, Crystal Filters, Output Attenuation)   (2Jan08)  
Click here to see a discussion of some stability issues.      (2Dec07)

Go to the bottom of this page to see info regarding the layouts.    

Roger, KA7EXM, has closed his on-line store and no longer has boards or kitlets.   Board photos are shown below for those still building.  We made a few minor modifications to the design over that in QST to help the builder.   You can see these in the applications page and the errata page.  A schematic is shown below.     


loaded circuit board
One of the boards loaded with components.   This was a "test" version of the project.  The resistors used in the board are 1/8 Watt with a size much smaller than 1/4 Watt.   None of the parts are stressed.   (The two resistors in the upper right corner are traditional 1/4 W so you can compare.)   The pot is mounted on the board.    The board layout accommodates this, but the pot will eventually be mounted on a receiver front panel.    Two resistors are replaced with wire jumpers; this was intended.   The pads are there to allow flexibility for the experimenter. No stability problems were noted with this board.    The problem of overall stability is considered by clicking here.   There is nothing critical about the transformer.  Since it is wound on a high permeability core, about any winding style is fine.     The differential pair, Q7 and Q8, are on the right side of the board about half way up from the bottom.   The modification "TeePee" is seen just above the pair.   See the errata for details.    Anyone wanting the layout should write me.

Schematic diagram on 2 Jan 08
This is the left side of the schematic diagram, as built for one of the parts kits.

Schematic of IF as built, 2 Jan 08.
And this is the right hand side of the schematic.   There are minor differences from the QST schematic.
Click here to see errata for the December 2007 QST article.

PCB Layouts     (26may13)

Although there are no longer commercially built boards, some folks are willing to make their own boards.  As a service, we are making our layouts available. Our boards were built via ExpressPCB.    This service is available on line from   Going to that site will allow a reader to download their layout program.  I find the program very easy to use.   Once the program has been downloaded, it can be used to view the two files, which are in the zip file below.   Note that there are some board updates that have been done to enhance stability, etc.   These are not in all of the boards.   

These layouts are offered as a service to those wishing to build their own boards and then to build a version of the IF amplifier.   But this is a HOMEBREW project for the reader.    We take no responsibility for accuracy -- you are on your own.   

To download the layouts, just click here and save the zip file to your computer.   The zip file includes a text file relating to the SMT layout, two layout files, and some figures that might be useful.