A batch of questions here really (if it helps I'm operating at 433.92MHz):
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How should I orient a helical antenna with respect to my board (i.e. my "ground plane") to get the best range performance?
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What should the dimensions of my ground plane have to be in order to get good performance / how much does this matter compared to orientation?
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I'm also wondering what effect (if any) the relative orientation of these types of antennas between the transmitter and receiver has on link quality (due to polarization?).
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Is the antenna pattern directional for these types of antennas (related to 3), and if so how narrowly?
Sorry if this question is a little bit all over the place – I've got an EE background, but RF can be kind of mysterious (if you know what I mean)…
Regards,
Vic
[Edit] 3-d visuals would be really helpful in helping me get my head around this as well [/Edit]
[Edit2]
5. Going to attempt some ASCII art here – what's the best way to mount my antennas? slashes (/) are the helix orientation, underbars (_) are the ground plane, and vertical bar (is the feed point):
Transmitter Receiver
**A**
/ /
/ /
/ /
/ /
____|____ ____|____
**B**
//////// ////////
_|_________ _|_________
**C**
//////// ////////
_|_________ ________|__
**D**
/
/
/
/ ////////
____|____ _|_________
**E**
/
/
/
/ ////////
____|____ ________|__
[/Edit2]
Best Answer
First, a caveat - I'm primarily a CE, so this is just my understanding of the matter:
1. Generally, the worst reception is when the antenna is upside-down, or nearly so, and the best is when it is vertical. However, horizontal orientations are nearly as good as vertical; the radiation pattern is usually something like this, with "up" in the picture corresponding to the positive Z axis (defects overemphasized):
2. Again, your antenna manufacturer will likely have a reference design for this. Sarantel publishes sample gerbers for many of its antennas. If the antenna is not directly coupled with a ground plane, near-field radiation will still be helpful.
3. No idea. I doubt that it would matter as long as both antennas had decent signal strength. Back-to-back might not be ideal, but everywhere else should work fine.
4. No, it's hardly directional at all.The reason you use a helical antenna is because you want near-omnidirectional performance. If orientation is controllable, use a different antenna.