On Feb 11, 2020, at 6:17 PM, Dave VE3LHO <dave@...> wrote:

?It is actually pretty nice isn't it? Gives me inspiration to make something as nice :-)

Ugly style is going to be my first attempt but I have 50 of the filters and a bunch of the inductors and caps (at pennies a piece I couldn't just order the 3~4 I really needed)? so I'm going to experiment. We'll see if the etched pcb works better (or worse) than my ugly version. Everything you say is true but none the less pcb are generally "better".

I am a little concerned about the SMA connector center pin rotating. In my case it would be both a cap and an inductor that could be destroyed and I am considering some kind of small small land at each connector so I can solder them.

Dave
VE3LHO

On Tue, Feb 11, 2020 at 08:10 AM, Jerry Gaffke wrote:

Erik,

Your ugly style SAW filter board is actually quite pretty!
And if you are getting 70dB of stopband suppression, plenty effective.

Could work better than many attempts at an etched board.
An etched board that only has a groundplane on the back
would need lots of feedthroughs to connect ground points.
Feedthroughs have inductance, and that groundplane is 1.5mm further away.
(In this case, an etched board could have an almost solid ground plane on the front.)

I have had that center SMA pin try to rotate when connecting a cable,
so I try to leave a land of copper at an SMA to solder the pin to.
Otherwise those caps can break.
An alternative might be some 1 meg resistors in a 1206 package
from center pin to the ground pins,?adding strength there.

Sufficient grounding as you have done is important.
Not obvious, but you have left copper under each SAW filter
connecting ?the two halves of the ground plane, that's important.
I'd probably leave the entire ground plane intact except for
a small island on each end for the SMA pin.

I would have thought it might need a shield through the middle?
to isolate one SAW filter from the other, but 70dB is good enough.

Jerry, KE7ER


On Tue, Feb 11, 2020 at 01:09 AM, <erik@...> wrote:

Maybe not as nice but building the filter dead bug style does deliver good performance.
The out of band rejection is at least 70dB, Combined with the SI4432 out of band rejection you get about 100dB which is sufficient.