[time-nuts] Fwd: Best replacement for Trimble Bullet antenna

Chris Albertson albertson.chris at gmail.com
Tue Nov 22 21:10:50 EST 2016

With roof mounted antenna practical issuers are important.

1) Do birds like to tech on it, they will it then can find a way to stand
on top of it.  They poop on whatever they perch on.
2) Same with snow in some places
3) Can you route the lead wire down the mast?   Some antenna mount to a
pipe flange allowing coax to be completely inside a metal cover.   The wire
will last a LONG time if it is not exposed to the elements
4) easy way to attach a ground clamp.
5) with a pole mount one can extend the height of the antenna as far up as
you like.

It is not hard at all to find a high gain GPS antenna that is inside a
pointed radome.   Mine is a helix type but I think a good modern patch
inside a pointed radome would work as well.   Practical issues dominate
unless you want to go up on the roof now and then.   I put the antenna up
and figure it is good for the life of the building, decades of not thinking
about it I hope.

On Tue, Nov 22, 2016 at 10:58 AM, Russ Ramirez <russ.ramirez at gmail.com>

> I have a used version of the subject antenna, which is still quite
> operational. However, I recently needed either a way to tie into reception
> from this antenna or purchase additional antennas. Given the cost of active
> patch antennas, I tried one from Adafruit.
> While comparing reception on a Trimble Thunderbolt to an integrated GPS
> module (used for time and PPS on a WSPR transmitter) is not apples to
> apples, I did notice how many more fixes the latter receiver obtains. For
> example, when the Thunderbolt has fixes on 6 birds, the YIC51612 (MediaTek)
> receiver module will have 10. I am sure the criteria is not the same for
> what constitutes a fix in both cases, but I also observed the following.
> By simply using a 0.1 uF SMD MLCC cap to couple into the Trimble Bullet,
> i.e. the Thunderbolt still powers the amp with +5v, but the signal has a
> path to my other GPS receiver, the bullet antenna underperformed by a
> significant amount. What's possibly worse is that the patch antenna is on a
> window sill, whereas the bullet antenna is on the roof with a clear view of
> the sky.
> I have not tried the Adafruit patch with the Thunderbolt yet as I will have
> to reduce the LNA voltage from 5 to 3.3 before trying the second test.
> The general question I wanted to ask though is what others use/like as roof
> mounted antennas? Are some of the 'Marine' antennas better?
> Russ
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Chris Albertson
Redondo Beach, California

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