[time-nuts] GPS shielding by power lines?

Henk ten Pierick henk at deriesp.demon.nl
Sun Aug 10 14:11:25 UTC 2008


Hi,

In car radio capacitive antennas are used. The required LNA rejection  
for the power line frequency is in the order of 100dB.

henk


On Aug 10, 2008, at 15:16, Alan Melia wrote:

> Hi Didier, thanks for that idea, yes they were all "pucks" all  
> Garmin two
> intended for marine use and one was a old Garmin GPSIIplus with a  mag
> "puck". I have a Trimble Palisade that I have not got round to  
> working on
> yet, but I understand that there are problems putting this version  
> into NMEA
> mode...so will have to be careful.
>
>  Thanks Alan G3NYK
>
> ----- Original Message -----
> From: "Didier Juges" <didier at cox.net>
> To: "'Discussion of precise time and frequency measurement'"
> <time-nuts at febo.com>
> Sent: Sunday, August 10, 2008 12:52 PM
> Subject: Re: [time-nuts] GPS shielding by power lines?
>
>
>> Alan,
>>
>> I don't believe you have said what type of antenna you are using.  
>> If you
> are
>> using a true timing antenna (Symmetricom, Trimble Bullet) I would  
>> expect
>> little or no direct effect from the power lines, but if you are  
>> using a
> puck
>> or other inexpensive commercial antenna (which have little or no  
>> filtering
>> or shielding), you may well be affected directly by the field from  
>> the
> power
>> line on the antenna itself. The Thunderbolt itself should have enough
>> filtering to protect you from a direct effect, the Thunderbolt has  
>> been
>> designed to be co-located with other equipment, particularly cell
>> transmitters, so I would expect it to be fairly immune to stray  
>> fields.
>>
>> Didier KO4BB
>
>
>
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