[time-nuts] Effects on GPS antenna performance due to installation proximity of second antenna

[jimlux]

On 11/23/19 5:23 PM, Bob kb8tq wrote:
> Hi
> 
> Most of what you see suggests > 10’ / 3M between GPS antennas. They seem to be concerned about
> a variety of things. Exactly how those concerns translates into the magic distance has always been a
> bit obscure.

3m/10 ft is "round number phenomenon".

For identical receivers, there's always the issue of LO leakage back 
through the antenna, and into the other receiver.  The LOs/clocks aren't 
going to be exactly the same (the crystals are probably 1ppm or 
something like that), so you wind up with a 1kHz tone on top of your PN 
code.

I suppose the same is generically true of any receivers.  I have 
experienced this both with disparate and identical receivers, back in 
1993 with handheld receivers (Trimble, Magellan) side by side, and newer 
ublox NEO-7



> 
> Bob
> 
>> On Nov 23, 2019, at 7:07 PM, JAMES ROBBINS <jsrobbins at earthlink.net> wrote:
>>
>> I would appreciate feedback on the question of the ill effects (if any) of mounting two GPS antennas in proximity to one another. I am intending to mount a 58532A L1 antenna and a L1/L2 antenna on the same mast on my roof separated by around 1-2 feet. I have attached a photo to show the intended installation.  (Mast is clamped into the right side aluminum channel.) My concern is “shading” of one antenna over the other.  Thanks for the consult.
>>
>> Jim Robbins
>> N1JR
>>
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