On the subject of range....
Your mobile antenna has no "gain", and if your ground is good to the car body (not a magnetic mount---mag mounts have a bad grounding component). Your "ground wave" range on flat area will be about 10 to 12 miles.
If you are on a 1,000' mountain top (for example)....your "ground wave" signal can extend out to say 50 miles...IF the frequency (channel) is clear of other louder, closer in stations to the other person.
"Skip" (which used to be illegal to communicate with stations over 150 miles, but no longer enforced) is a totally different story.
The nature of 27 mHZ is that it is controlled by SO MANY DIFFERENT forms of radio propagation it's not even funny. Let's look at some of the most common...
Sunspots
Sunspot Cycles (we are currently at the absolute LOW of the latest 13 year cycle) transequitorial propagation on 27 mHz is rare. The MUF, or Maximum Useable Frequency for LONG distance comms rarely goes higher than 14 or 18 mHz....wait until late 2008 and it will improve. This propagation takes place in the "F" layer of the ionisphere.
Sporatic E
Sporatic E lies in the slightly closer to the Earth "E" layer of the ionisphere. At 27 mHz...these invisible "clouds" can be as amall as a large city or as big as a state, and allow even low powered stations to communicate between 300 and 1,000 miles. The openings usually happen from April to July in the Northern Hemisphere...and can last for up to 3 to 4 hours. This propagation does NOT depent on the solar cycle.
Meteor Scatter
Meteors, usually only the size of a grain of sand bombard our planet on a daily basis...but are more OFTEN in nature in regularly predictable meteor showers. The meteors "ionize" the upper atmosphere as they burn up...at 27 mHz, they allow contacts from say 300 to 600 miles, but only for a VERY SHORT period of time...say 30 to 60 seconds. Make your transmissions very short, and you can make many meteor contacts during a meteor shower.
Atmospheric Ducting
Usually over larger bodies of water. The signal gets "trapped" in the "D" layer where the temp aloft is equal to the temp aloft over a distance of say 70-125 miles away and gets "trapped" in that layer (like a heating duct) until it gets to "escape" some distance away. This makes contacts from (i.e Chicago to Grand Rapids over Lake Michigan in the summer) possible.
Aurora
The Aurora Borealis as low frequencies can wipe out radio propagation. At higher frequencies it can actually help. I've made many contacts with Russians at 14 mHz "over the pole", and the Aurora on their signals was obvious...it throws the signal out of phase, and it sounds "watery" or like they are talking underwater.
At 27 mHz, the signal can get "bounced" off the Northern Aurora, and end up send the signal back South 1,000-2,000 miles. The signals sound less watery, but with the "bouncing" there is a slight delay echo, and sometimes you can hear your own last sylable of your own transmission in the delay echo. Aurora is less common than the other forms of propagation, but low power stations can easily have a Chicago-California-Florida round-table discussion where all three stations can easily hear one another---almost impossible with other forms of propagation at 27 mHz.
Really, the best way to improve your signal strength LEGALLY (and keep you from getting a hefty fine from running illegal power) is to improve your antenna ststem. a 102' whip does a lot better than a short mag mount on a mobile.
If you run a base station, there are literally a hundred different antennas with "gain"...many you can build yourself cheaply from wire that will GREATLY improve your signal LEGALLY.
I built a 6 element quad with wire and gray PVC tubing and hung it at 70'...the gain was astranomical. The cost = less than $100
With ALL of the forms of propagation above you DO NOT NEED ILLEGAL POWER! I have easily communicated with other stations at half the power people have in their garage door openers (.050 mW).
Let me know if I can help.
68ROX
K5TEN
