GPS speedometer question

I have read several threads/tutorials on GPS speedometer based on NEO-6M GPS module. I still have one question. The antenna has a very short cable. But tutorials say to mount the antenna on the roof. Where can I get this antenna with a long cable? Thank you.

PS: My arduino skill level is still basic. I run engine cooling fans with arduino nano.

Put the entire GPS module on the roof and run an extension cable for the serial connection between the GPS module and the Arduino.

Much easier to organise that way.

I’m running an UNO and a NEO 6M, and the short antenna cable. All is mounted in a plastic box and it works well inside the car.
Lots of trees, especially whet trees affects the GPS. It works the same well in the railcar I drive.

Hi Paker.
I’ve been using various antennae and I find the square ceramic one with the short wire (10 cm) performs best by far.

For a long while I played around with the stubby screw-in type, the magnetic puck that sits on the roof with a 3m cable and even just lengths of plain wire. All worked but I came to accept long times to get a fix as normal (10 to 30 minutes). I was jealous of railroader’s claims of getting a fix within a minute.

Now it’s normal for mine to get the time within a minute & a fix within 2 or 3 minutes. The unit sits on the dash secured with double sided adhesive tape (never use blutack - it leaves ugly residues you can’t remove). It even sometimes gets results indoors.

I did a 200km trip today. The device worked well except for a few minutes when it was wet and plenty of trees.

Stick with it - it makes a great driving aid.


Thank you for the advice. I will keep the antenna and NEO6M together and try both locations, dash and roof. I have follow-up questions.
Q1. The goal of this project is to turn on the engine cooling fan when speed is near zero. During the few minutes until gps fix, is there a GPS-not-ready indicator?
Q2. I read about getting speed from OBD2 with ELM reader and OBDuino. Please comment on this project. Or any other project to get vehicle speed.
Thank you.

Q1. Yes, the GPS outputs a field that specifies if the data is valid or invalid. You can use that. You will need to learn about NMEA sentences.

Q2. I had an OBD2 that transmitted its data via Bluetooth. There are several Android apps that can display all the data graphically. I don’t know OBDuino.

I also used a Hall Effect sensor to determine speed. Very reliable and consistent. Always available, unlike GPS. Drawback is you have to install it underneath the car as well as a magnet on a drive shaft. I’m happier with the GPS unit.

Thank you. I will check out both options, Bluetooth OBD2 reader and NEO6M gps module. I think I have received sufficient advice to get this project going now.