Recent Publications:
High-accuracy Time and Frequency in VLBI (updated 2023) presented at the International VLBI Service for Geodesy and Astrometry (IVS) Technical Operations Workshop (TOW) meeting on May 1-4, 2023 at MIT Haystack Observatory by Katie Pazamickas, Paraton, and Richard M. Hambly, CNS Systems, Inc.
Click here to download the PDF version of the presentation.
Archived Publications:
Timing for VLBI (updated 2019) presented at the International VLBI Service for Geodesy and Astrometry (IVS) Technical Operations Workshop (TOW) meeting on May 5-9, 2019 at MIT Haystack Observatory by Katie Pazamickas, Paraton, and Richard M. Hambly, CNS Systems, Inc.
Click here to download the PDF version of the presentation.
Timing for VLBI (updated 2017) presented at the International VLBI Service for Geodesy and Astrometry (IVS) Technical Operations Workshop (TOW) meeting on April 30 through May 4, 2017 at MIT Haystack Observatory by Katie Pazamickas, Harris; and Richard M. Hambly, CNS Systems, Inc.
Click here to download the PDF version of the presentation.
Timing for VLBI (updated 2015) presented at the International VLBI Service for Geodesy and Astrometry (IVS) Technical Operations Workshop (TOW) meeting on May 4-7, 2015 at MIT Haystack Observatory by Katie Pazamickas, EXELIS; Dr. Tom Clark, NVI; and Richard M. Hambly, CNS Systems, Inc.
Click here to download the PDF version of the presentation.
Timing for VLBI (updated 2013) presented at the International VLBI Service for Geodesy and Astrometry (IVS) Technical Operations Workshop (TOW) meeting on May 6-9, 2013 at MIT Haystack Observatory by Dr. Tom Clark NVI/NASA GSFC and Richard M. Hambly, CNS Systems, Inc.
Click here to download the PDF version of the presentation.
Low cost GPS-based time and frequency products, an update presented at the 44th Annual PTTI Meeting on November 26 - 29, 2012 in Reston, Virginia, USA.
ABSTRACT: The performance of low cost GPS-based time and frequency products continues to improve. Our initial use of these products was to provide a cost effective solutions to the problem of epoch synchronization and performance monitoring of the hydrogen masers at isolated stations in the global Very Long Baseline Interferometry (VLBI) network. Now these products are also used in a wide variety of applications such as providing network time for CDMA cell sites and secure isolated data networks, providing general purpose high accuracy timing at isolated locations, synchronization of RF transmitters for shared spectrum applications etc. Motorola and iLotus GPS timing modules (the VP, UT+, M12+ and M12M series) have been the basis for many timing products over the years. The latest of these, the M12M, is now a mature product although an end of life has not been announced. We report here on a new OEM module that has been developed to replace these aging units maintenance of existing and current production products and in new applications. This module is designed as a drop in replacement that is functionally, mechanically and electrically equivalent to the M12M. To insure compatibility, it emulates the Motorola commands and messages. These new modules are based on the uBlox 6T GPS engine. In addition to compatibility with the M12+ and M12M, the receiver offers programmable xPPS signals, smaller quantization errors due to higher clock speed, quantization corrections reported with picoseconds resolution, and a 50-channel engine. These new u-blox based M12 compatible OEM modules are available now and are priced competitively with the original module. This paper reviews the improvements this family of products has achieved over the years and looks at the performance of the new generation of low cost timing engines as they compare with the most recent previous generation.
Using Low-Cost COTS Software Defined Radios for Phase Cal and RFI Monitoring presented at the International VLBI Technology Workshop on October 22-24, 2012 at Haystack Observatory by Dr. Thomas A. Clark, NASA Goddard Space Flight Center (Retired), Greenbelt MD.
ABSTRACT: Many years of VLBI experience have shown that station problems can often best be diagnosed by using a spectrum analyzer or communications receiver to "see" or "listen to" the IF (baseband) RF signal. In the Mark-3 and -4, we often offset one LO by 10 kHz and monitored the 10 kHz phase cal tone with a a simple LC filter and scope. We could use an HF radio to listen to the phase cal tone or to an RFI signal. With the Mark-5 and their Digital Back Ends, we lost access to these basic analog monitoring points. With invaluable inputs from Russ McWhirter, the latest RDBE code includes the ability to observe the sign bit from any of the 32 PolyPhase Filter Bank (PFB) channels. The one-bit sample gives us the ability to monitor any frequency in the 32 MHz wide PFB IF. In the past few years, experimenters in the Radio Amateur community have developed a number of SDRs that can be used spectrum analyzers with resolution bandwidths (RBW) in the sub Hz-range. In this paper I will describe and demonstrate several commercial, off-the-shelf SDRs suitable for VLBI use that are available in the $500-$2500 range.
Next Generation GPS Timing for the Mark 5 Era presented at the International VLBI Technology Workshop on October 22-24, 2012 at Haystack Observatory by Dr. Thomas A. Clark, NASA Goddard Space Flight Center (Retired), Greenbelt MD and Richard M. Hambly, CNS Systems,, Inc.
ABSTRACT: Abstract: The performance of low cost board-level GPS-based time and frequency products continues to evolve. Our initial use of these products was to provide a cost effective solutions to the problem of epoch synchronization and monitoring the performance of the hydrogen masers at isolated stations in the global Very Long Baseline Interferometry (VLBI) network. Now these products are also used in a wide variety of applications such as providing network time for CDMA cell sites and secure isolated data networks, providing general purpose high accuracy timing at isolated locations, synchronization of RF transmitters for shared spectrum applications etc. Motorola and iLotus GPS timing modules (the VP, UT+, M12+ and M12M series) have been the basis for many timing products over the years. The latest of these, the M12M, is now a mature product approaching end of life. We report here on the development of a new OEM GPS module to replace these aging units for maintenance of existing and new applications. The new module is designed as a drop in replacement that is functionally, mechanically and electrically equivalent to the M12M. To insure full compatibility, it emulates the Motorola commands and messages. The new modules are based on the replacement module, which is Swiss uBlox 6T GPS engine. In addition to compatibility with the M12+ and M12M, the receiver offers programmable xPPS signals, smaller quantization errors due to higher clock speed, and higher resolution "sawtooth" quantization corrections. The new uBlox based, M12 compatible, OEM modules are available now and are priced competitively with the original Motorola/iLotus modules. For nearly two decades, the HP/Agilent 53131A and 53132A time-interval counter, in conjunction with CNS Systems TAC32 support software, has been the low-cost "standard" for user in VLBI. Agilent has declared the 131/132 to be a "dead" unsupported product. We will report on our evaluation of several new, low-cost, compatible counters that are now supported in Tac32Plus and are suitable for use in future Mark-5 VLBI systems
Low-cost, High Accuracy GPS Timing
presented at the Institute of Navigation's GPS 2000 Conference, September 20, 2000 by
Dr. Thomas A. Clark, NASA Goddard Space Flight Center, Greenbelt MD,
Richard M. Hambly, CNS Systems Inc., Severna Park MD,
and Reza Abtahi, CNST, San Jose CA.
Get a
copy of the paper here.
Click here to download the PDF version of the presentation.
Timing for VLBI presented at the International VLBI
Service for Geodesy and Astrometry (IVS) Technical Operations Workshop
(TOW) meeting on March 12, 2001 at Haystack Observatory by Dr. Thomas A. Clark,
NASA Goddard Space Flight Center, Greenbelt MD.
Click here to download the PDF version of the presentation.
Critical Evaluation of the Motorola M12+ GPS Timing Receiver vs.
the Master Clock at the United States Naval Observatory, Washington DC.
presented at the 34th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting
on December 3, 2002 at the Hyatt Regency, Reston VA
by Richard M. Hambly, CNS Systems, Inc.
Get a copy of the paper here.
Click here to download the PDF version of the presentation.
Timing for VLBI (updated 2003) presented at the International VLBI
Service for Geodesy and Astrometry (IVS) Technical Operations Workshop
(TOW) meeting on September 21-24 2003 at Haystack Observatory by Dr. Thomas A. Clark,
NASA Goddard Space Flight Center, Greenbelt MD and Richard M. Hambly, CNS Systems, Inc.
Click here to download the PDF version of the presentation.
Timing for VLBI (updated 2005) presented at the International VLBI
Service for Geodesy and Astrometry (IVS) Technical Operations Workshop
(TOW) meeting on May 9-12 2005 at Haystack Observatory by Dr. Thomas A. Clark,
NASA Goddard Space Flight Center, Greenbelt MD and Richard M. Hambly, CNS Systems, Inc.
Click here to download the PDF version of the presentation.
Timing for VLBI (updated 2007) presented at the International VLBI
Service for Geodesy and Astrometry (IVS) Technical Operations Workshop
(TOW) meeting on April 30 - May 3, 2007 at Haystack Observatory by Dr. Thomas A. Clark,
NASA Goddard Space Flight Center, Greenbelt MD.
Click here to download the PDF version of the presentation.
Timing for VLBI (updated 2009) presented at the International VLBI
Service for Geodesy and Astrometry (IVS) Technical Operations Workshop
(TOW) meeting on April 27-30, 2009 at Haystack Observatory by Dr. Thomas A. Clark,
NASA Goddard Space Flight Center, Greenbelt MD and Richard M. Hambly, CNS Systems, Inc.
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Timing for VLBI (updated 2011) presented at the International VLBI
Service for Geodesy and Astrometry (IVS) Technical Operations Workshop
(TOW) meeting on May 9-12, 2011 at Haystack Observatory by Richard M. Hambly, CNS Systems, Inc. Timing for VLBI (updated 2013) presented at the International VLBI
Service for Geodesy and Astrometry (IVS) Technical Operations Workshop
(TOW) meeting on May 6-9, 2013 at MIT Haystack Observatory by Dr. Tom Clark NVI/NASA GSFC and Richard M. Hambly, CNS Systems, Inc.
Modern & New Spectrum Analyzers for the Mk-5/VLBI2010 World |
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Improving the Performance of Low Cost GPS Timing Receivers
presented at the 38th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting
on December 7, 2006 at the Hyatt Regency, Reston VA
by Dr. Thomas A. Clark, NASA Goddard Space Flight Center (retired), and Richard M. Hambly, CNS Systems, Inc.
Click here to download the PDF version of the presentation.
Classic HP Application Notes
GPS and Precision Timing Applications, Application Note 1272.
The Science of Timekeeping, Application Note 1289.
What's all this VLBI stuff, anyway? presented at the International VLBI
Service for Geodesy and Astrometry (IVS) Technical Operations Workshop
(TOW) meeting on April 30 - May 3, 2007 at Haystack Observatory by Dr. Thomas A. Clark,
NASA Goddard Space Flight Center, Greenbelt MD.
Click here to download the PDF version of the presentation.
Other Important Publications:
Quartz Crystal Resonators and Oscillators
For Frequency Control and Timing Applications - A Tutorial
by John R. Vig, November 2008.
Motorola M12+ GPS Receiver User’s Guide
Prepared by Synergy Systems, LLC., 2004.
AMSAT Publications:
AMSAT OSCAR-E, A New LEO Satellite from AMSAT-NA
by Richard M. Hambly, W2GPS
as published in the AMSAT Journal, Volume 25, No. 3, May/June 2002 and
in CQ/VHF Magazine, Summer 2002.
Get a copy of the paper here.
This is the presentation given at the Maryland-DC area AMSAT Meeting and Space Seminar,
Sunday, May 5, 2002, at NASA Goddard Space Flight Center, Greenbelt MD.
Click here to download the PDF version of the presentation. This is the presentation given at the AMSAT Forum. Hamvention 2002,
Saturday, May 18, 2002, HARA Arena Complex, Room 1, Dayton OH.
AMSAT OSCAR-E Project Status Update, A New LEO Satellite
from AMSAT-NA
by Richard M. Hambly, W2GPS
as published in the AMSAT Journal, Volume 25, No. 7, Nov/Dec 2002 and
in CQ/VHF Magazine, Winter 2002.
Get a copy of the paper here.
Get a copy of the viewgraph presentation here.
This is the presentation given at the 20th Space Symposium and AMSAT-NA
Annual Meeting, Saturday, November 9, 2002, at the Lockheed Martin Recreation
Area (LMRA), Fort Worth TX.
Microsat Design, What Do People Want?
by Richard M. Hambly, W2GPS
as published in the AMSAT Journal, Volume 25, No. 7, Nov/Dec 2002.
Get a copy of the paper here.
Click here to download the PDF version of the presentation. This is the presentation given at the 20th Space Symposium and
AMSAT-NA Annual Meeting, Saturday, November 9, 2002, at the Lockheed Martin
Recreation Area (LMRA), Fort Worth TX.
AMSAT OSCAR-E Project, Summer 2003 Status Update
by Richard M. Hambly, W2GPS
as published in the AMSAT Journal, Volume 26, No. 4, Jul/Aug 2003 and
in CQ/VHF Magazine, Summer 2003.
Get a copy of the paper here.
Click here to download the PDF version of the presentation.
This is the presentation given at the AMSAT Forum, Dayton Hamvention 2003
on Saturday, May 17, 2003, at HARA Arena Complex, Room 1, Dayton, Ohio.
AMSAT OSCAR-E Project, Fall 2003 Status Update
by Richard M. Hambly, W2GPS
as published in the Proceedings of the AMSAT-NA 21st Space Symposium,
November 2003, Toronto, Ontario, Canada.
Get a copy of the paper here (requires Adobe Acrobat Version 5 or newer).
Click here to download the PDF version of the presentation.
C-C RIDER, A New Concept for Amateur Satellites
by Tom Clark, W3IWI
as published in the Proceedings of the AMSAT-NA 21st Space Symposium,
November 2003, Toronto, Ontario, Canada.
Get a copy of the paper here (requires Adobe Acrobat Version 5 or newer).
Click here to download the PDF version of the presentation.
C-C Rider Revisited
by Tom Clark (ex W3IWI, now K3IO), Bob McGwier (N4HY), Phil Karn (KA9Q) and Rick Hambly (W2GPS)
as published in the Proceedings of the AMSAT-NA 22nd Space Symposium,
October 2004, Arlington, Virhginia.
Get a copy of the paper here.
Click here to download the PDF version of the presentation.
Eagle Software Defined Transponder Milestone On Tuesday, August 16, 2005 Tom Clark W3IWI, Rick Hambly W2GPS, and Bob McGwier N4HY (left to right in this picture ) made the first ever live contacts via the prototype Eagle satellite Software Defined Transponder (SDT). The SDT software was written by Frank Brickle AB2KT, and Bob McGwier N4HY. The transponder was set up in Rick's lab (shown) and the contacts were made from Rick's Ham shack, completely independent of the lab. Hear the historic contact.
Software Defined Transponders, Future AMSAT Missions: Phase 3E and Eagle
by Tom Clark (K3IO, ex W3IWI) and Bob McGwier (N4HY)
as presented at the 10th Annual SVHFS Technical Conference in Greenville SC, April 28 & 29, 2006
Get a copy of the paper here.
AMSAT North America, A Status Report by Richard M. Hambly W2GPS, AMSAT President, as presented at various conferences in the Spring of 2006, most recently at AMSAT-DC Meeting and Space Seminar, April 8, 2006, Historical Electronics Museum, 1745 West Nursery Road, Linthicum MD 21090 Get a copy of the PowerPoint presentation here.