Another happy Part 15 Broadcaster! Be sure to share your stories – happy or sad – with Part15.us!
Our latest contributor writes:
After reading as much as possible about part 15 radio, I took the plunge…
Another happy Part 15 Broadcaster! Be sure to share your stories – happy or sad – with Part15.us!
Our latest contributor writes:
After reading as much as possible about part 15 radio, I took the plunge…
I purchased a Gizmo FCC compliant 100mw AM transmitter and went on the air. I get good range (1.75-2 miles radius easy despite lots of trees and a low height above average terrain), I am legal, and having lots of fun.
Despite articles describing the importance of height, I put my antenna in the attic along with the transmitter as I felt that I could make any needed adjustements there, and this has proven to be a good decision.
I was going to get a copper pipe to make an antenna, when I noticed my old uhf yagi antenna in the corner of the attic, so I just turned it to a vertical position, and let that be my (5′ more or less) antenna.
Then I bought a round trash bucket at wal mart, wound a few hundred feet of wire around it to make a loading coil, used a few twists for tuning taps, and attached it to my upright yagi. I based this loosely on some articles I had read.
Then reading more about grounding, I found an article about elevated radials (from 1938!), so I strung about 8- 50′ elevated copper wires as elevated ground radials ( in the attic of course), used a TWO FOOT LEAD, and let that be my ground.
To check my radiated power, I applied an amperage rated LED to the coil, and later a multimeter to check current, and then used ohm’s law to calculate approximate radiated power: It seemed compliant, at no more than 100mw… Editor’s note – The regs actually specify 100mw power into the final stage, but this app looks good!
Considerations: you need to fiddle with the antenna and ground to get distance. Just a slight difference in connections (use the tuning taps), will make all the difference.
The level of sound into the transmitter makes a difference in range– despite reports advising otherwise, I find running my computer driven audio feed into the transmitter on the high side of volume gives more range even if it leads to a little over compression w/in 150 feet of the transmitter. Editor’s note – YES – modulation intensity is a big factor in AM broadcasting.
And you must have a sensitive radio on the receiving end (good car radio w/ antenna). Lots of fun-not lots of $$$
That 1938 story I referenced regarding elevated ground radials was really from 1937 article imbedded in an article at www.commtechrf.com/ambroadcast.htm.
By the way, I neglected to mention my capacitance hat, made out of a paper plate wrapped in aluminum foil and then mashed between my vertical uhf tv antenna turned part 15 am antenna, and the roof.
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