Sunday, February 22, 2015

9Mhz IF LO PASS FILTER (whew)

First time I've done this so I can't swear to how well I thought it through or really any aspects of the entire thing LOL.  I'm trusting the design at this point.  The results on-air seem impressive though.

I wanted to see if I could clean up the output RF from the 9 Mhz IF out of the FTDX-5000 which then goes into my new HF Upconverter to help reduce images, and noise, and misc trash in the spectrum prior to upconvertion.

I went to CoilCraft and downloaded their "Low Pass Filter Designer" software (free) and designed a 7 Pole (7th Order Low Pass Elliptic) filter.  I ordered their inductors from the design directly from CoilCraft.  Then ordered the required Caps from Mouser.

Below is a screen shot of the design.



Following are some photo's of the constructions.  This was VERY difficult for me since I don't have tools to work with SMT parts that are the size of 4 grains of pepper!  Literally.

BUT I did manage to get it built, and after retouching some bad solder joints it seems to be working very well.  I plan to include a real plot from a VNA setup I have eventually.  But that'll be a while as setup for that takes too much time at this point.  

This is a strip of sticky copper tape 1" wide top to bottom, turned upside down so I could hold the Inductors in place while I tacked them with solder. (not pretty, but like I said it's not easy either without the proper tools)


This is some double sided copper clad PCB.  I trimmed away the copper on in the middle on both sides so as not to effect the inductors.  Then cut slots for solder pads to match the layout of the inductors I tacked together in the above photo.

Top side completed.  With caps added.


Bottom Side with Caps added.