[time-nuts] Re: GPS failed

[Bob kb8tq]

Hi



> On Jul 13, 2022, at 6:50 AM, Björn via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 
> 
> Sent from my Phone
> 
>> On 13 Jul 2022, at 02:34, Bob kb8tq via time-nuts <time-nuts at lists.febo.com> wrote:
>> 
>> Hi
>> 
>> The “typical” Symmetricom cone shaped GPS antennas are targeted at 
>> cell phone tower applications. Being mounted on the same structure
>> as multiple cell transmitters puts them in a significant RF environment. 
>> They have a *lot* of filtering built into the antenna to try to prevent overload
>> issues. 
>> 
>> As with a lot of things, Symmetricom simply rebrands antennas made by
>> others. Not all cone shaped antennas are identical. However it’s a pretty
>> good bet that most of them are very similar to what Symmetericom ( and
>> the other folks ) supply for cell applications. 
>> 
>> The “other end” of the range are the multi band saucer shaped “survey” 
>> antennas. They tend to have a lot less filtering and be more focused at 
>> allowing the user to access a wide range of frequencies ( both GNSS and
>> supplemental services) via a single device. Lots of filtering also tends to 
>> mess up delay here or there, that’s not a great thing for high precision 
>> work. 
>> 
>> Bob
>>> 
> 
> Bob,
> 
> That was true 10-15 years ago. Good quality surveying antennas often has quite decent filtering on each band they are designed for. 

Quite true of the stuff we pay $2K for. The eBay surplus or the $100 antennas
from China …. I’m not so sure of.

Bob


> 
> /Björn 
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