[time-nuts] Antenna mounting location

Bob Camp kb8tq at n1k.org
Wed Mar 9 07:11:49 EST 2016


Hi

Which way does the awning face? Are there any obstructions between the antenna and the horizon? 

The problem is that something large , flat and metallic makes a pretty good reflector at microwaves. Your awning is many wavelengths on a side, so it will act as a reflector. 

If you have an obstruction, *and* the signal reflects, you get multi-path. Since the reflected path is longer than it “should be” you get an error in the solution. Each meter of added path gives you up to 3 ns (up to because you may have multiple sat’s in the solution). A refection off the far end of your awning could be in the 15 to 30 ns range. 

Will you have errors on every sat every minute of the day? Of course not, it’s a two factor thing. They will come and go as the constellation moves in the sky. You will get some pattern of frequency / time errors as a result. 

What’s the answer? 

Get the antenna as high above the “reflector” as you can. That puts the reflections as far below the base and as far into the “low gain” part of the pattern as you can.

Bob

 

> On Mar 8, 2016, at 5:40 PM, Steve <steve65 at suddenlink.net> wrote:
> 
> Hello all,
> 
> I have a Trimble Bullet GPS antenna. Is the performance of those antennas affected if they are mounted adjacent to an aluminum awning? The awning is about 8ft X 15ft. The antenna would be a few inches to a few feet above the awning. My first thought is that the antenna performance would not be affected by the awning but thought I'd ask before moving ahead with it.
> 
> Thanks.
> 
> Steve, K8JQ
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