Helical antennas and orientation

Question

A batch of questions here really (if it helps I'm operating at 433.92MHz):

1. How should I orient a helical antenna with respect to my board (i.e. my "ground plane") to get the best range performance?

2. 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?

3. 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?).

4. 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]

Answer 1

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.