110704-1134 EDT
scottp628:
Even if you could get an extremely good ground connection, whatever that might be, what will that do to protect the transmitter?
How is the transmitter powered?
How is the signal being transmitted connected to the transmitter?
Where is the transmitter located relative to the antenna?
How long is the antenna?
Do you have any understanding of what is inside of a transmitter, how the antenna is connected to the internal electronics, and how one tries to protect a transmitter?
Some time ago I did a search with some of the results being:
A search using .... ground rod resistance earth .... on
www.google.com produced the following useful sites
http://www.ees-group.co.uk/downloads/LEC-Green- Grounding Manual.pdf
....... good on theory, modification of soil with salts ( NaCl, table salt ), and multi-rod spacing
http://www.eng-tips.com/viewthread.cfm?qid=21381&page=8
....... interesting, to an extent surface area should make a difference, one person claims 1 ohm
http://www.hubbellpowersystems.com/powertest/tips_news/pdfs_best/05-2002.pdf
....... some theory, values, errosion of rod, galvanized
http://www.www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=18;t=004764
....... several different contributers, a question on worms getting fried
http://www.msha.gov/S&HINFO/TECHRPT/GROUND/GROUNDRE.HTM
....... gov report, tough to get as low as 5 ohms, good discussion on how to
....... measure rod to ground resistance
But really this these do not address the lightning problem. Just suppose you could achieve a resistance to somewhere in the earth of 1 ohm. Suppose the direct lightning current is 1000 A. What is the voltage of your grounding electrode relative to that someplace in earth? 1000 V.
Let your transmitter and its power source and any other connections to bring data into the transmitter be totally contained inside a copper box, and only the antenna is exposed outside of the box. If a protective shorting device is placed from the antenna to the copper enclosure such that no voltage will be produced inside the box that would damage anything in the box, then it does not matter what potential the box is raised to relative to any reference point there will be no damage to internal components. I assume this is an AM transmitter in the normal broadcast frequency range. A 15 W transmitter is not much of a transmitter and not very expensive.
A good discussion on transmitter and receiver protection from direct lightning strikes was at:
http://www.harvardrepeater.org/news/lightning.html
....... about ham radio lightning protection
but it is now gone.
What he described was running everything into the house thru a bulkhead at one location with LC filtering on each wire, and I believe some spark gap, and MOV shunts.
But, for a 15 W transmitter in a temporary location is it worth any great effort.
Study Faraday shields, MOVs, LC filters, etc. Ground rods in rock are not your solution.
.