So, I have now designed the filter board and calculated the values of each of the 6 filters. I have some 1000V silver dipped mica capacitors that I’m going to use, and have been adjusting the toroids to match them 100%. I decided to use 5 element low pass filters in stead of the 7 element commonly used. I saw the design in the Ameritron ALS-600/1300 and according to Elsie filter modelling software they should work fine. PLEASE comment if you have something to say about this decision. I will post the filter calculation later when I finish transferring them from Elsie to some better form.
While @work, I played around making a block diagram of the amplifier + some front panel ideas.
The complexity of the control board startled me, I see that I have to multiplex some of the input/output. The 16f877 has 8 AD inputs, 2x full 8 bit GPIO. I’m compiling a list of all IO and I will probably for simplicity use one of the 8 bit bus for controlling the LCD. I want to keep the serial UART unused for future expansions (remote control), then I have to figure out how to get the band data from the xmit, I have some old QST article showing a PIC based antenna switch so I will probably just use that design. Using a 74hc374 tristate latch to multiplex one of the data buses will probalby be the choice.
I plan to fire up the amplifier next week for testing and start the output module into a dummy load. I will probably use a manual bandswitch to control the filters. I’m NOT going to start operating the amplifier without the control circuits, but I have xmas to look forward to now.. I finally have something to do ;P
So the info I’m now starting to look into is the ALC circuit, and the band data input from the transceiver.