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Leiser (Automotive)
21 May 09 3:33
Hello,

I designed a FM "LNA" using a two-layer PCB and worked fined. I was thinking to reduce the cost of the PCB by using a one-layer PCB and removing the ground plane on the bottom layer. I would route the ground connections on the top layer. I have found with PCB manufacturer that cost reduction from two-layer pcb to one-layer is around 27%.

Do you think the amplifier will work without ground plane?
VE1BLL (Military)
21 May 09 8:30
FM broadcast band (-108MHz) isn't that high. So there's no reason that it couldn't be made to work, but it might require more careful design, analysis, testing and design cycles to ensure that it remains stable (not oscillating). Also, the board area might grow thereby negating some of the savings (probably quoted on a 'per unit area' basis).

Might be easier places to save pennies.

 
Helpful Member!  zappedagain (Electrical)
21 May 09 12:02
A lot of designers did single sided PCB layouts for AM and FM radios when I worked at Tandy (Radio Shack) all the time.  A trick I used was to delete any power and ground symbols off the schematic and wire them up.  That gives a much more intuitive feel for where your ground currents are flowing and how you need to route them.  

On a single sided design you will probably end up needing to install a few jumpers.  You'll need to take that additional cost into account as it will offset your PCB savings.  

John D
 
Leiser (Automotive)
22 May 09 3:12
Thanks guys. You gave me two very useful hints. Size and extra jumpers to take into account in price.

Thanks again. I´ll let you know if eventually I manage to do it and save cost.
Comcokid (Electrical)
22 May 09 19:13
I assume since price is your goal, then your product is high volume. As pointed out, 108MHz FM only takes careful layout with your components to achieve an adequate 1-layer layout. To make it even less expensive, go to a composite glass/epoxy (CEM-1 or PC=75, aka 'appliance board') or phenolic PCB.

For high volume, these are not drilled, but are punched. Composite glass/epoxy boards are a common material for low cost in the US. Phenolic are the low cost boards used in Far-East made consumer items. I have seen RF circuits done with 1206 SMT type components as well as axial. Buy several inexpensive TV antenna boosters and take a look.
zappedagain (Electrical)
1 Jun 09 16:54
Ah, 1206 parts!  Vintage 1995 design!  Been there, done that!  It is amazing how long these simple designs stay in production.  The price point of 0603s should have somebody in Japan looking at a redesign of those circuits about now to shave a few more pennies out of the cost...  

John D
 

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