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gocat9

GP antenna dimensions and use

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Hi,

I too am going to make several of these antennas. I have a couple of questions and a comment.

Questions1: Does anybody have the actual dimensions in mm (or inches for those 'other' folk!) of the two elememts? There are potential inaccuracies taking measurments from the drawing. Sometimes it is easier working from the actual numbers instead.

Question2: Has anybody tried using this antenna as a transmitting antenna (on 2.4GHz of course)? Any reasons as to why it may be unsuitable?

Comment: When changing the design for a different frequency, I don't think you scale EVERYTHING as the instructions say. For example, you don't scale the SIZE and SEPARATIONS of the holes for the SMA connector. Also, you don't need to scale two of the three dimensions for the element separator insulating material: only the dimension providing the separation (ie 0.2" one). As far as I can see, the other side lengths are arbitrary and not needed to scale.

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You can use a patch on the Transmitter. However, that is not practical for R/C wireless video use, which is the target application. If your application is fixed line-of-sight, then it would be fine.

It is not technically required to scale the width and length of the air dielectric insulator (the thickness/height must be scaled). However, if the GPP antenna's dimensions are scaled up, the insulator will probably deserve larger bonding area for the adhesive and to provide support (big sheet metal plates can become flimsy). So, scaling all dimensions is a reasonable thing to do.

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Thanks for that. Yes, my application is pretty much fixed and LOS, especially if the -3dB points are about 80deg!.

Since I have access to very accurate drilling machines etc, does one see any performance issues if instead of gluing the elements together with a spacer, I drill four small holes (say 1/8" or 1/16") in both elements and attach them using teflon nuts and bolts and a very accurately cut-to-length spacer?

As long as the holes in the driven element do not affect tuning, resonance, impedance etc in any way, it would seem to me that this would have at least two advantages.

1. It would allow very precise and fool-proof alignment AND positioning of the elements relative to each other (since they are fixed by the holes in each plate).

2. Secondly, disassembly would be much easier if required later.

Any comments appreciated.

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Teflon hardware is compatible with microwave applications. Drilling holes in the elements is a concern, (use small diameter hardware as proposed). Innocent modifications like these might impact performance, so it might be wise to also build a stock antenna to act as a validation control.

Adding the hardware for dielectric adjustments is not necessary if you are not interested in spending a lot of time trying different spacings. The design is very broadband with the spacing that is currently used. Larger spacing is not advised, however you can narrow the bandwidth by going with closer spacing.

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I plan to do some comparative range tests with this antenna vs a dipole and will report back to the forum when completed.

On measuring the driven element (smaller plate), it appears that it is not exactly square (neglecting the cutoff corners). It can't be my printer because the reflector element comes out square. Does this appear correct?

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