I have been very interested in building both of Paul’s Broadband RF Amplifiers utilizing the 6AH6 and 6AH9 circuits. I decided to combine both projects in the same chassis, and chose to use external filament and B+ supplies using bananna jacks. I plated a double-sided section of copper PC board with Liquid Tin, then drilled a hole and soldered a wire on both sides and mounted it to the chassis to form a shield between both sections. The 6AH6 takes input from a BNC and outputs to another using the identical Carlson circuit. In the 6AH9 circuit, I added a switch-selectable optional tuned LC network utilizing 11 different inductor values fed into one section of a 525pf variable tuning capacitor to ground to form a wide tuning range on the input circuit. This can be added in by a toggle switch and then tuned both by the inductor switch position and/or the capacitor. On the output, I added a switch-selectable option to place a second section of the tuning capacitor (also 525 maximum value) in parallel with the output coil. Output is fed into either a BNC or to a removable antenna coil; I purchased an old AA5 radio external antenna coil that works perfectly. The coil is mounted on pressboard that is easily removed by wing nuts; different antennas can be utilized throughout the 30Mhz range. Another unique feature is that the filament supply lines, B+, and input signal are all switch-selectable to direct them to either the 6AH6 or 6AH9 sections as needed using a 4-pole switch for complete circuit isolation. I tried to pay special attention to such details as capacitor polarity, lead length, signal interference and grounding. The project is built into a Hammond chassis with bottom plate for complete shielding. I built this unit mainly for use when performing allignment on AA5 radios. Tested utilizing a 1kHz signal with AM 400Hz modulation; the unit works great with an extremely strong signal as heard on a radio placed 10 feet away. The separate tuning sections allow a very sensitive signal peak. The unit produces usable output down to a 10mv input signal – very responsive. Been working on this one for almost a year; much of that time was in obtaining hard-to-get parts. This is my first post here and I do not see how/where I can post photos so if someone can tell me how, I’ll post them. Thanks guys, more projects to come!
Hi, there is a section on this forum (I believe is under the General Chat section) where MCL hymself has posted some “official” instructions/suggestions on how to post pictures:
https://mrcarlsonslab.com/community/general-chat/uploading-pictures-to-this-forum/#post-1611

