Friday, December 15, 2017

Back to the SDR rRig: Band and Low-Pass Filter Boards

I doubt anyone really likes winding toroids, and I'm no exception.  But, unless you're in a position to hire someone to do it for you, you gotta suck it up and get it done, which is what I've been doing for the last three nights.

Below is a pic of the nearly completed bandpass filter and low-pass filter boards for the SDR-2017.   Nothing high-tech about 'em, just capacitors, coils and relays.

I think I mentioned in a prior entry that I'd basically stolen the basic design of the filters from those used in the IC-735, though I did massage them a bit using LT-Spice.

If you look carefully at the boards, you'll see that I'm using Manhattan style construction using small round pads.  I kind of stumbled onto the idea of making these pads after ordering some el-cheapo PCB stock that doesn't like being cut with shears, which is how I've always made Manhattan pads in the past. 

Amongst my seldom used tools is the hole-punch set pictured below.  I found that, by inserting the PCB stock into the punch upside-down, I was able to consistently knock-out perfect circles in various sizes.  I've used Rex Harper's ME Pads and like them, so to pay tribute to Rex, I call these "My Pads".

Hole punch used to create Manhattan Pads. 1/8" pad shown near the face of the ball-peen hammer.

Inverted cheapo PCB stock in punch. I found it necessary to punch the stock from the backside, otherwise the phenolic tended to shatter.

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