Is there any maps out there that will give you the distance of how many watts will carry on the fm band.
Say up to a 100 watt transmitter. I hope to start up a station soon with about 5 watts and see how far that would travel. I know the terrain and buildings will be a factor.
Other question is what is a good antenna to mount in my back yard on a 40ft mast to get about 5 mile or less in coverage? I see the comet antenna 5/8 antenna is mentioned that is good. I'm looking for an antenna that will work good if possible in all directions.
The answers to the questions you pose are theoretical at best.... The ONLY real way to tell "how far a signal carrys".....is to actually check signal strength with a professionally-calibrated field strength meter at various distances from the transmitter... Something few of us Average Joes have - or can afford!!! The next best thing is just checking signal with a portable/car radio -- measuring "audio quality" in the same fashion as the field strength meter... GENERALLY SPEAKING.....you will have the best luck with your antenna IN THE CLEAR, AS HIGH ABOVE TREE/BUILDING LINE AS POSSIBLE!! Transmitter power can be deceptive....increasing power 10X results in a gain of 3db....In other words, a 20 watt transmitter will NOT "automatically" "go twice as far" as a 10 watt unit..... HAAT (Height Above Average Terrain) is also a factor in maximizing signal coverage...my antenna is ~40' UNDER a small grove of oaks and birches, and only about 8' off the ground... BUT....the entire antenna/tower structure is~ 700' above average terrain on the side of a hill....with 20 watts I "hit" my town with ~75% full-quieting coverage...IN STEREO!! Never used the Comet....but have read some decent reviews on it...I'm using a single-bay CP unit from Singapore (yeah, eBay....!!!) that does really well -- and is rugged enough to stand up to our Northeast winters!! End of the day....set up with MINIMUM transmitter power, MAXIMUM antenna height...and DON'T SKIMP on the feedline!!! A roll of Radio Shack CB coax just WON'T hold up!! Squeeze those nickels and get a length of LM400 with COMPRESSION-FITTED connectors -- try to match the connectors ON THE CABLE, without having to use "adapters" that can result in signal loss and/or SWR "bumps"... Good luck with your project!!
Thanks for the info I guess a ride in the car within a 5 mile radius will have to do and see how far 10 watts carry.
My antenna will be on a 30 foot mast with antenna on top so hoping to reach the 5 mile radius. I live here in the Northeast on the coast about 5 miles from Boston and just hoping to hit some of the local small town I think there is about 8 cities within the 5 mile radius I'd like to hit.
I need to ask another question where and what is a good low pass filter to use for the 88-108 mhz fm band for transmitting. Something that will handle 0-150 watts?
IMHO.....I wouldn't worry about a low pass filter if you're using less than 100 watts of power.... Years ago an FM station I was working for took a bad lightning hit....it fried a section of hard line AND the low-pass filter.... The filter was temporarily bypassed with a section of hard line (the output power WAS dropped to ~500 watts from 1500.....)until repairs could be made.... While not "strictly legal", it DID keep us on the air -- and no "birdies" or parasitic emissions were ever detected.... If you really want to pursue getting a low pass filter....keep an eye on used broadcast equipment sites...post a "Wanted" ad here: www.thebdr.net/hotlinks/forsale.html Keep in mind....whatever filter you find is likely to have flanges that will require REDUCERS in order to use them with, say, "N" connectors... In MANY cases the reducers can cost more than the FILTER!!! Good luck!
