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8640Jr – Building the Low Pass Filters

 

8640Jr – Building the Low Pass Filters

I selected a small enclosure for the low pass filters. It was a little challenging getting all 4 filters into the small box, but it turned out pretty good. I started running out of room on the circuit board, so I started mounting the resistors standing up for the last couple. This photo was taken before I installed the final coupling cap from the switch to the output connector.

 
Low Pass Filter Assembly

I used a pencil to help hold the toroid while I wound the coils. I got the idea from an article that I saw that said to use chopsticks. I didn’t have any chopsticks, but the pencil worked fine, and was much easier than trying to hold the toroid in my fingers.

 
Pencil toroid tool

First (Band 4) Filter built…

 
Band 4 Filter

Here is a close-up of the Band 4 filter. Note that I used 4 capacitors in the center PI leg, as I didn’t have 200pf capacitors, so had to use parallel 100 pf capacitors for each 200 pf called for…


 

Band 4 Low Pass Filter Close-up

 

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