[time-nuts] Re: Regarding GNSS antenna radomes... (Motorola Timing 2000...)

[Bob Camp]

Hi

If you get fancy enough, your antenna should have data on the phase vs arrival angle. That can get tossed into the solution on the receiver to improve the result. 

If you are talking about a 10 mm error, the timing contribution is going to be pretty small. Even more so with a GPSDO that is not being fed after the fact correction information. 

Back in the days Motorola spec’d in these antennas, SA was still turned on. The contribution from these antenna was *way* down the list of error sources back then. 

Bob

> On Aug 7, 2024, at 9:07 AM, Bill via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Hi,
> 
> The antenna phase center will vary depending on the angles of incidence - and timing will depend somewhat on this.  Phase center variation is mainly a function of antenna design, but radomes will affect this as well.  A good reference antenna will have a phase center that will remain within mm or sub mm over its main radiation lobe.
> 
> 
> Cheers
> 
> Bill
> 
> 
> On 07/08/24 09:03, Ulf Kylenfall via time-nuts wrote:
>>  
>>   Regarding these:
>> It was disovered at the Onsala Space Observatory, that when using cones as radomes, the precisionof the timing/positioning signals was impaired by the uneven refractionof signals reaching the internal antenna structure from satellites of differentaltidudes/angles.
>> This when using antennas from Leica. The internal structure of the offered items may of course be different.
>> 
>> At the Onsala Space Observatory, the cones was replaced by spherical radomeswhich improved the performance both for Swepos (Swedens nationalgeographic positioning system) as well as the support structuresused for geodetic VLBI.
>> A true time-nut will of course be exploring the use of spheres for his/hersown timing and frequency standard lab set up...
>> 
>> :-)
>> 
>> Cheers
>> Ulf Kylenfall - SM6GXV
>> SR Research Engr, (Ret)Onsala, Sweden.
>> 
>> 
>> 
>> 
>> 
>> 
>>   1. Motorola Timing2000 GPS “L1” Antenna (Gregory Beat)
>> 
>> 
>> ----------------------------------------------------------------------
>> 
>> Message: 1
>> Date: Sat, 3 Aug 2024 09:45:39 -0500
>> From: Gregory Beat <w9gb at icloud.com>
>> Subject: [time-nuts] Motorola Timing2000 GPS “L1” Antenna
>> To: time-nuts at lists.febo.com
>> Message-ID: <A5EFC6E2-AF19-43B7-8BA1-7A2CDBF6C870 at icloud.com>
>> Content-Type: text/plain;      charset=utf-8
>> 
>> These Motorola brand GPS “L1” antennas (circa 2000) have appeared on the Surplus market (used, eBay, elsewhere), as Mobile/cellular sites perform upgrades.
>> Prices / condition range from a Used few $$ to New in Box at $100 + .
>> 
>> Electronic Goldmine (Scottsdale, AZ) has listed the Motorola Timing2000 GPS antenna (they don’t know model) and
>> it’s matching Motorola Pole Mount at Electronics Surplus in Mentor, OH
>> 
>> Motorola GCNTM20A3A : Timing2000 Antenna (Outdoor), Goldmine.
>> https://theelectronicgoldmine.com/products/g28183
>> <snip>
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