meeting Thursday 27th November: A Practical Guide to GNSS Receivers by Mike Dunstan G8GYW

[John Gumb]

Folks,

Next club meeting is on Thursday 27th November.

Our very own Mike Dunstan G8GYW will kindly give us a practical guide to GNSS receivers.

AI informs me that "GNSS stands for Global Navigation Satellite System, which is any satellite-based system that provides positioning, navigation, and timing (PNT) services. It consists of a network of satellites that broadcast signals, allowing receivers on Earth to determine their precise location, speed, and time. Common examples of GNSS include the U.S. Global Positioning System (GPS), the European Galileo system, and the Russian GLONASS."

Venue: 2nd Woodley Scout Group, Vauxhall Park, Vauxhall Dr, Woodley, Reading RG5 4EA https://what3words.com/bowls.blame.lace .

Eyes down: 8pm.

Zoom info at the end.

Mike's talk will look at the features of the different models available covering: 

• Which ones to avoid
• How to tell if they are genuine
• How to set them up for best reception
• How to program them for typical amateur applications
• (GPSDO, WSPR TX time/location, UTC clock)

As ever, refreshments (tea/coffee) will be available as usual with a generous supply of biscuits. Please bring a mug if you wish to partake. You are also welcome to bring along your favourite tipple.

73

John

G4RDC

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Reading and District Amateur Radio Club is inviting you to a scheduled Zoom meeting.

Topic: A Practical Guide to GNSS Receivers by Mike Dunstan G8GYW

Time: Nov 27, 2025 08:00 PM London

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[John Gumb]

See you on Thursday!

73

John

G4RDC

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[mi...@dunstan.uk]

Hello everyone

Some interesting questions were raised at the club talk last night which I was unable to answer at the time, but following some research this morning I can provide the following information.

CURRENT CONSUMPTION

The typical current consumed by the ublox receiver models discussed is given in the table below for a receiver in Tracking mode. The newer models are better suited to portable operation, although the M8L (often sold on ebay as an M8N) has a small penalty due to the onboard automotive components. Turning off Automotive Dead Reckoning alone is not a reliable way to reduce this — instead use a single constellation, lower update rates and the u-blox power-saving configuration messages.

Model	Current
NEO-6M	39mA
NEO-7M	17mA
NEO-M8N	23mA
NEO-M8L	29mA

START-UP TIMES

ublox define three start-up modes: Cold, Warm and Hot. Which one is used depends on how long the receiver has been off for and whether the onboard battery-backed RAM (BBR) is still valid.

Condition	Result
Off < 4 hours, BBR retained, RTC running	Hot Start
Off > 4 hours, ephemeris expired	Warm Start
Time lost or BBR lost	Cold Start

The acquisition times in the various modes are listed below for a receiver tracking GPS satellites. Note that for Galileo the Cold and Warm starts take almost twice as long.

Model	Cold Start	Warm Start	Hot Start
NEO-6M	27s	27s	1s
NEO-7M	30s	28s	1s
NEO-M8N	29s	Not specified	1s
NEO-M8L	30s	Not specified	1.5s

According to ublox, movement of the receiver of around 50km or more during an off period would force a Warm start.

I hope that helps!

Mike G8GYW

[Colin Ashley]

Thanks Mike, really useful info and a great presentation👍 

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