[time-nuts] Getting my Rockwell D200 GPS to work

David davidwhess at gmail.com
Sat Jan 7 13:05:16 EST 2012


The 1/4 wave of 1.5 GHz is about 5 centimeters.  I would expose that
much of the center conductor and then angle the shield wires (also 5
centimeters) down at 45 degrees into a cone which will be 135 degrees
from the center conductor.  Use a very short feedline and use it
outdoors.  It will not be pretty or high performance but it will be
cheap in money and time and may restore sanity.

On Sat, 7 Jan 2012 11:25:19 -0600, "Don Lewis"
<dlewis6767 at austin.rr.com> wrote:

>How long a wire?

>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of David
>Sent: Saturday, January 07, 2012 11:17 AM
>To: Discussion of precise time and frequency measurement
>Subject: Re: [time-nuts] Getting my Rockwell D200 GPS to work
>
>I am not suggesting this as a replacement for a proper GPS antenna.  I
>am suggesting it as a inexpensive sanity check.  The loss from
>receiving a circularly polarized signal with a linearly polarized
>antenna (or the reverse) is 3db.
>
>On Sat, 7 Jan 2012 17:29:54 +0100, Azelio Boriani
><azelio.boriani at screen.it> wrote:
>
>>Just take care that GPS signal is right-hand circularly polarized. For
>>those interested in building GPS antennae I recommend the QFH-type antenna:
>>quite complex but it is the same antenna actually used to transmit from the
>>birds.
>>
>>On Sat, Jan 7, 2012 at 5:02 PM, David <davidwhess at gmail.com> wrote:
>>
>>> I have done the same thing with an amplified patch antenna facing out
>>> the window.
>>>
>>> I wonder in this case if making a rough 1/4 wave antenna out of a very
>>> short feedline would be enough for a cheap outdoor sanity check.
>>>
>>> On Sat, 7 Jan 2012 14:21:09 +0000, shalimr9 at gmail.com wrote:
>>>
>>> >I test all my GPS receivers with a hockey puck type antenna attached to
>>> the wall in my hamshack, which is upstairs, but under the ceiling and the
>>> roof and I have never had one fail to lock within reasonable time. With
>>> this setup, Thunderbolts occasionally go on holdover, but never for very
>>> long.
>>> >
>>> >Of course, when I plug them in the external Symmetricom antenna, they
>>> typically see more satellites and don't go into holdover.
>>> >
>>> >I am in Northwest Florida, so probably at a lower latitude than most of
>>> you, so the same setup farther north may not work as well.




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