[time-nuts] Best replacement for Trimble Bullet antenna

Nick Sayer nsayer at kfu.com
Tue Nov 22 22:58:04 EST 2016

I bought a Gilsson marine antenna and an 8 port amplified splitter on eBay. The antenna is mounted on the roof of my garage, where it has visibility easily down to 20 degrees except to the North where there is an obstruction (but that doesn’t matter). The coax is 10 meters of whatever came with the antenna. My reception with this setup is as close to ideal as I’ve ever heard of. At the moment, gpsmon on my NTP server shows 5 satellites with 50+ SNR, another 5 with 40+ and one at 22 (7 degrees elevation).

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