[time-nuts] Best replacement for Trimble Bullet antenna

Bob Camp kb8tq at n1k.org
Wed Nov 23 08:07:49 EST 2016


Ummm …. errrr …. radio transparent plastic. You want to avoid making a 
lens that distorts the paths over the antenna so it’s not just an issue of transparent. 
You also want it to be “clear” (non distorting). You need it to be stable in terms of UV,
humidity and temperature. The guys who made the antenna didn’t have it quite so tough, 
they could design the cover as part of what determined the pattern of the antenna.  

The short list of what your low cost printer will handle:


If it is really low cost, it will only handle the first one. All are a bit of a 
disaster at 1.5 GHz. PLA likely will not hold up outdoors, let alone do well at RF.
The other two are poor at RF. 

The longer list on a higher priced printer:


The last two are out right from the start. One dissolves in water, the other has no structural integrity. Nylon is hydroscopic 
and not all that great at 1.5 GHz. For what ever reason the polycarbonate that they sell also is a bit hydroscopic. It also is 
quite challenging to print unless you have a very fancy printer. 

Certainly not an easy thing to do.


> On Nov 23, 2016, at 1:05 AM, Nick Sayer via time-nuts <time-nuts at febo.com> wrote:
>> On Nov 22, 2016, at 9:39 PM, Dennis Lloyd <dlloyd at musi-tronics.com> wrote:
>> Your problem will be Birds and Debris, it is flat and you will have interruptions and phase shifts.
>> Did you not understand why we use pointed antennas for timing and fixed installations.
> No, I guess I didn’t.
> That said, our cats seem to be doing a good job discouraging any birds, and I can see the antenna mornings when I go out to the car and there’s been no debris problem I’ve been able to detect.
> If it were required, I’d suspect it would be fairly easy to 3D print a pointy hat from radio-transparent plastic.
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