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

[John Wettroth]

One other possible glitch- is the antenna track at the top of your layout below supposed to come back and join the ground plane?, this is usually how these antennas are done.  Now I’m afraid I’m getting out of my depth- worth a check.
 
Regards,
John M. Wettroth
(984) 329-5420 (home)
(919) 349-9875 (cell) 
From: TriEmbed <triembed-bounces at triembed.org> On Behalf Of John Wettroth via TriEmbed
Sent: Friday, October 29, 2021 12:05 PM
To: 'Scott Hall' <scottghall1 at gmail.com>; TriEmbed <triembed at triembed.org>
Subject: Re: [TriEmbed] Does my Raspberry Pi LoRa modem board look ready to send off to OSHPark?
 
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 <mailto: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 <mailto:triembed at triembed.org> >
Cc: Adam Novak <interfect at gmail.com <mailto: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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