[time-nuts] Thunderbolt - trouble locking with some types of antennas

Jerry jsternmd at att.net
Mon Jul 31 13:19:12 EDT 2017

Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
antenna placed indoor near a window facing South
 can’t get much worse but
most of the time it will be locked onto 3 or 4 satellites.    I recently
bought a www.leobodnar.com <http://www.leobodnar.com>  GPSDO for my SDR ham
radio setup.  I was very surprised to find that this minimalist GPSDO using
a small patch antenna with internal LNA placed near my window had satellite
& PPL lock within a few seconds.  It requires 3-4 satellite locks for its
PPL.  However, when I attached the patch antenna to my Thunderbolt –
satellite signal strength were zero or minus for all satellites.  The specs
for the patch antenna are listed below.


I would appreciate any advice understanding this behavior.


Jerry NY2KW


Center Frequency 1575.42MHz±3 MHz

V.S.W.R 1.5:1

Band Width ±5 MHz

Impendence 50 ohm

Peak Gain >3dBic Based on 7×7cm ground plane

Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)

Polarization RHCP


LNA Gain (Without cable) 28+/-3dB

Noise Figure 1.5dB Typ.

Filter Out Band Attenuation (f° =1575.42MHz)

7dB Min f0+/-20MHZ

20dB Min f0+/-50MHZ

30dB Min f0+/-100MHZ

V.S.W.R <2.0

DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other

DC Current 5mA /11mA/15mA Max




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