Building a SAM - notes for prospective builders


I built my SAM in December 2003. The quality of the kit is absolutely outstanding. All parts are well packed and delivered in individually labelled bags.

SAM on test


The kit went together very well - but follow the instructions supplied on the website.
I did encounter a few problems. Peter - PA1SIX - has noted these and will update the instructions in due course, but for posterity, here they are.

It is also clear that the SAM can detect when the garage door is open! The diagram hereshows two vertical lines, the first is the garage door opening, the second is the garage door closing again. The door is about 5m due West of the Sensor.. :-( However, I have realised that the garage door has a magnet installed as part of the house intrusion detection system - since replaced by a microswitch. - Which I have since noticed hasn't made the slightest bit of difference!

The next step is no bury the detectors in the back garden. I have bought some sheathed 5 core power cable. This will be run into the back garden and the sensors buried about 600mm deep. More if I can get through the clay.


2003/12/30 - Fitted a second sensor in the same tube as the original, so I am now measuring X (N-S) & Y (E-W) vectors of the Earths Magnetic Field. After leaving the sensor in the back garden for the last few days, I have now buried the tube in the back garden. The base of the tube is about 450mm down on a very solid clay bed! I have covered the tube in fine sand.to stabilise it and hopefully keep it thermally stable as well.

I have fed the sensor box with 5 core (3 phase) screened cable which I purchased from my local electrical retailer. The box is now 10m from the shack - it can still detect the garage door being opened but now the effect is far less obvious on the graphs..

11 January 2004. The By data is still too unstable although Bx is almost acceptable. I have pulled the unit out of the ground and filled the box full of builders expanding foam. Hopefully, this will improve both the thermal and vibrational stability. The unit has been buried another 100mm deeper as well. It is now about 600-700 mm deep at the base.

My website is on a Linux box, but the SAM-data and graphic images are produced on a Windows box. I use the following script to copy the data from the Windows 2000 server to my Linux Web Server.

#-----------------------------------------------------------
# ScriptName: samcopy.sh
# PURPOSE:    To transfer SAM images to sam directory - run every 10 minutes using CRON
# AUTHOR:    21-DEC-03  M Kinder
#
#
#
#  Requires :-
#     samba to be available
#     for the mount point /mnt/samdata  to have been created
#
#==============================================================
#
#set the home directory for all scripts to run from
HOME=/usr/local/httpd/htdocs/astro/sam
#
#-----------------------------------------------------------
# Set Other Environment Variables
#-----------------------------------------------------------
ADMIN=martyn@czd.org.uk                               # email address for messages
ERRFILE=/var/log/messages                          # Error file
#
#-----------------------------------------------------------
# Mount the samba share on /mnt/samdata
#-----------------------------------------------------------
/usr/bin/smbmount //sirius/samdata /mnt/samdata -o username=sam,password=sampw,workgroup=samz
#
#copy the data
cp /mnt/samdata/sam_data.png $HOME/sam_data.png
chmod 640 $HOME/sam_data.png
#
# ---------------------------------------------------------
# CLOSE THE LOG and unmount the share
# ---------------------------------------------------------
/usr/bin/smbumount /mnt/samdata

Finally, many thanks to Peter, Lutz and Dirk for helping me get this wonderful bit of kit working.