EMRFD Message Archive 11921

Message	Date	From	Subject
11921	2015-12-03 09:12:50	larry_n0sa	Single or double sided PCB ?
I am building a small low power transceiver which will be surface mount parts. I am using .032 pc board because I plan to etch the boards myself and that is the system I am using. Should I use double sided board? I only plan to uses traces on one side. If I use double sided board, what is the difference in reaction to the ground plane between the .032 and the .062 boards? Thanks Larry n0sa
11922	2015-12-03 10:40:24	dixonglennb	Re: Single or double sided PCB ?
A popular and good technique for RF is to not etch the second side (mask it with tape when etching) and use it for a ground plane, drilling a hole and soldering a wire through for all ground connections.  This gives you a nice low inductance ground. At anything under a gigahertz or so the pcb thickness shouldn't make much difference.  Good luck with your project and 73, Glenn, AC7ZN
11923	2015-12-03 11:48:31	Nick Kennedy	Re: Single or double sided PCB ?
I generally paint or tape the back side so it doesn't etch away and I can use it for a ground plane, even with single sided board designs. One caution though -- in the area of frequency determining components such as in a VFO, etch away the back side to get rid of the stray capacitance. The capacitance itself isn't that big a problem, but its poor temperature coefficient will cause drift. 73- Nick, WA5BDU
11924	2015-12-03 12:48:32	Dave	Re: Single or double sided PCB ?
Larry:   Having a ground plane is a thing.  If you need to run 50 ohm lines, you need a ground under the conductor.  You didn't state what the substrate(epoxy glass, teflon, etc) is.  Going from .064 to .032 makes the 50 ohm conductor half the width.  For FR4 board, a conductor approx .1" wide over a ground plane will be 50 ohms.  With a .032" FR4 board, the width is approx .05" to be 50 ohms. Dave - WB6DHW
11925	2015-12-03 12:57:14	bob_ledoux	Re: Single or double sided PCB ?
For through hole boards I use single sided board. The board exterior and areas around traces remain connected for ground plane. Like Nick, I use double sided board for SMT construction. Wire vias are used to make make ground connections on the unetched side. For off-board voltage connections I prefer to use right angle 0.100 spaced single row headers. I cut the bottom angle to about .125 inches long and solder them to pads sized for the purpose.  Connections to the board are made with Molex-style sockets or by wrapping with wire wrap wire. My signal lines tend to be made with small 50 ohm coax, soldered directly to the board.  I'm looking at SMT SMA connectors for quick disassembly. Plastic 2 inch wide packing tape makes good board etching protector.  But there may be a bit of etchant leakage around the board edge. With some thought off-board wires can be reduced.  For example, the pins on a pot can be bent so they solder directly to pads on the board's edge.  For example, look at Jim Kortge's receiver at the Four State QRP group.  All six of the off board functions are mounted on the board. Four State QRP Group Four State QRP Group Four States QRP Group View on www.4sqrp.com Preview by Yahoo   bob-N7SUR
11926	2015-12-03 15:01:25	larry_n0sa	Re: Single or double sided PCB ?
Thanks for the advice. Looks like it is double sided for this project. Larry n0sa
11928	2015-12-04 01:41:16	bubnikv	Re: Single or double sided PCB ?
An additional case, where the shielding plane may be counterproductive is the high gain audio amp of a DC receiver. I once had to drill some of the ground plane away to get rid of the audio oscillations aka howl. 73 Vojtěch OK1IAK
11936	2015-12-04 14:28:30	Ancel	Re: Single or double sided PCB ?
I just rec'd my 2003 published copy of EMRFD...I guess I'll have to go thru the errata as a 1st item. On the matter of PCB fab and detail etching etc, have a look at my Hackaday projects on the subject. https://hackaday.io/project/7938-pcb-smt-maker-lab-home https://hackaday.io/project/3363-apache-al13p-laminator-one-pass-pcb-toner-xfer this is also interesting: https://hackaday.io/list/8087-gigahertz-projects Ancel
11940	2015-12-05 08:25:19	Ancel	Re: Single or double sided PCB ?
Hmmm, that sounds like a ground loop in action. Perhaps that PCB required a star ground config.