[TriEmbed] Does my Raspberry Pi LoRa modem board look ready to send off to OSHPark?

[John Wettroth]

The microstrip track with all the via fencing looks too narrow.  I assume this is supposed to be a 50 ohm line?  You might check this- I assume this is on FR4 at 1.5 mm (.062”), if so, a 50 ohm track is about 3 mm wide (.125”).  A narrower track will give you a higher impedance line, this line looks more like a 100 ohm line.  If it’s a matching section, ignore my comment, but if its supposed to be 50 ohms, check it.  You might also consider putting some via stitches around the perimeter of the planes- they’re kind of floating RF wise at the edges except perhaps at the top and at the fencing.  I’m sure your initial design will work as is- but the narrow track will create some mismatch loss (range) and the lack of perimeter stitching can cause RF leakage- kind of a slot antenna that will radiate in the plane of the board- could give a squirrelly radiation pattern.  If the module vendor has a recommended layout, I would study it carefully and use it as much as possible.  Also, is any local bypassing recommended external to the module on power lines, etc.?  Something like a 10 nF 0805 and a bulk 1 uF ceramic would seem wise and cheap.  That 3.3v line is an inductor- not so bad really but dying to have a shunt C at the module end to make a proper “bias T” kind of structure.  Have fun.
 
Regards,
John M. Wettroth
(984) 329-5420 (home)
(919) 349-9875 (cell) 
From: TriEmbed <triembed-bounces at triembed.org> On Behalf Of Scott Hall via TriEmbed
Sent: Friday, October 29, 2021 3:35 AM
To: Triangle Embedded Computing Interest Group <triembed at triembed.org>
Cc: Adam Novak <interfect at gmail.com>
Subject: [TriEmbed] Does my Raspberry Pi LoRa modem board look ready to send off to OSHPark?
 
Question from Adam Novak <interfect at gmail.com <mailto:interfect at gmail.com> >, posed at 9:26pm 28-Oct-21:
Anybody here know PCB design? Does my Raspberry Pi LoRa modem board look ready to send off to OSHPark?

 
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