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ground/power plane

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arod

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Could anyone here give me a description of what these terms mean and if/when they are necessary when building PCBs. What I have in mind is constructing a couple of PCBs for wireless data transmission via those cheap 433 Mhz modules. The reason I ask is because I have heard these terms tossed around and not really well explained.
 
In geometry a plane is defined by any three points which are not all on the same line. In general terms it is synonymous with a flat surface. So in a PCB a ground plane is a flat metal surface which is at ground potential. Similarly a power plane is a flat metal surface which is at some non ground potential, such as +5V. They are used in multilayer PCBs to provide a low impedance path from Vcc and GND pins back to the power supply.
 
I suppose it depends on the frequency, the power supply, the coupling mechanisms, and a thousand other things. Why do you ask? Are you thinking of building single layer or double layer boards with the 433 MHz. modules?
 
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In his case I think the ground plane might be for the counter poise of a whip style antenna. Without a good ground plane, usually right under the chip you get very poor RF performance.
 
There is a great deal of trial and error in RF Engineering, and the test equipment required to characterize and debug systems can be ruinously expensive. It is folly to avoid techniques that are known to be beneficial for some supposed cost benefit. That you are even asking this question reveals how far in over your head you are.
 
It's good to be in over one's head though papabravo, that's the only reason I know anything at all about electronics in the first place. The module you purhcase should have recommendations for VCC and ground planes, and if the antenna is a whip (usually is) at the very least you should pay attention to having a good ground plane nearby, even if it's just a piece of issolated foil under the PCB to give the whip it's proper counter poise. I don't know the commended size or orientation of the antenna itself in relation to the ground plane but the PDF files should explain it.
 
I just want to see my first pcb project to work somewhat. The devices and their associated circuitry really isn't very difficult to understand. The manufacturers data is lacking quite a bit. I fail to see how I am in over my head for doing a small project like this. I just have little experience with high frequency electronics, but you have to start somewhere... The reason I asked is because I didn't want my first attempt to be on a multilayered PCB.
 
I don't know weather your plan will work or not. What I am suggesting is that you should be prepared for complete, absolute, and utter failure to get something working on the first try. You should also have some idea what your response will be when that happens. Our greatest successes are born from our worst failures. If you can afford that luxury then by all means charge ahead with your current plan.
 
A picture is worth a thousand words, so try this:

The attached photos are of a multiplier board out of an old, long dead, 166Mhz (??) transmitter/receiver.

Look at the component side, the large areas of tinned copper are a "ground plane". You will see that there are some areas where there are islands in the groundplane for component connections, but most of the connections are made on the "wiring side" of the board.

Using a groundplane like this gives a common point with low inductance between different areas of the board. minimising stray coupling between stages.
When the board was in use, the coils had screening cans around them, and the screening cans were soldered to the groundplane.

JimB
 

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UHF is notoriously tricky* and not for the faint hearted. For a 1st project you would be advised to use a tried and tested design and copy the layout exactly. Even then it's not guaranteed to work.

Once you got something thats working then you can start to experiment.

*That's why many amateurs and home experimenters stick to modifying pre- built modules or commercially made units
 
While I am a prime example of how long it takes to learn RF practices (it took me a long time), the fact is that you have to start somewhere so this project seems as good a place as any. While everything said is true, that you have to be mentally prepared for full or partial failure on the first try when you are beginner, I want to encourage everyone to try RF electronics whenever you can. You will learn so much. The best way to learn RF quickly is by having an RF mentor available to you who can explain the principles of what you are trying to do and then the principles behind why it doesn't work yet. Mentors often have some test equipment that you might be able to borrow too.
 
arod said:
What I have in mind is constructing a couple of PCBs for wireless data transmission via those cheap 433 Mhz modules.
Depending on the modules, you may not have to worry about RF beyond antenna design because most of them have all the RF circuitry on the module and every other pin coming off it is in the DC/audio range. ie: All the RF design has already been done for you. Checkout Nigel's tuts on one type of RF module:
 
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