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

Russ Ramirez russ.ramirez at gmail.com
Tue Nov 22 13:58:43 EST 2016

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?


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