Simple RF circuit board design

[Martin]

I've recently been tinkering with making HF filter PCBs so I was really
interested in it.  It is aimed at working in microwave which hams should be
doing more of.   I would like to hear more of the "black magic" that was
left out.

I'm a cheapskate and appreciate the faster turn around with two layer
boards.  I'm willing to learn how to make two layer work for simple
things.  I'm going to break rule #1 - "use four layers" for now.  A
Hackaday comment was the reference designs are frequently on two layers.

Some of it doesn't seem to be applicable to HF/VHF/UHF.  I tried rule # 2 -
"integrated components" and opened up the Digikey catalog for filter
chips.  Just a handful in the sub-microwave region and not available in
small quantities.  I know you can ask for samples but most of the parts
didn't seem that useful.

I've been working on some filters for RTL-SDRs - input 75 ohms.  I looked
up the recommended trace width for OSHPARK two layer stackup at 14 MHz and
it was over a 100 mils wide for 50 ohms.  That would take up a lot of board
space and may be impossible for complex circuits.  So sometimes rule # 3 -
"50 ohms everywhere" is hard to do.

I can't argue with 4 - "follow manufacturer's recommendations" .

I was surprised by rule # 5 - "route RF first".  Sounds like a good idea
but not nearly enough.  I though that totally segregating RF and digital
was the goal and where possible ground via walls are a good idea.

Any thoughts or black magic lessons welcome.

73 Martin W6MRR

On Wed, Mar 23, 2016 at 4:11 PM, Maitland Bottoms <aa4hs at amrad.org> wrote:

> This showed up today:
> http://hackaday.com/2016/03/23/michael-ossmann-makes-you-an-rf-design-hero/
>
> A few rules and a video describing example projects.
> Discuss.
>
> 73 de aa4hs
> -Maitland
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