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Just completed a combined project melding the 6AH6 and 6AH9 Broadband RF Amplifiers in same chassis

 
(@postfive)
New Member

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! 

 

 


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Topic starter Posted : 25/01/2025 6:30 pm
RadTekMan and Ovi4 reacted
Ovi4
 Ovi4
(@ovi4)
Honorable Member

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


This post was modified 1 year ago by Ovi4
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Posted : 26/01/2025 11:43 pm
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