Hence the higher frequencies for FM radio. He built the first station in 1939, but FM did not become really popular until the 1960s.
#RADI OBAND TUNER IMAGE TV#
By 1949, a million people owned TV sets, and by 1951 there were 10 million TVs in America.įM radio was invented by Edwin Armstrong in order to make high-fidelity (and static-free) music broadcasting possible. Television stations were pretty much non-existent until 1946 or so, which is when the FCC allocated commercial broadcast bands for TV. (The predecessor to the FCC was established by Congress in 1927.) In the 1920s, radio and electronic capabilities were fairly limited, hence the relatively low frequencies for AM radio. The first radio broadcasts occurred in 1906 or so, and frequency allocation for AM radio occurred during the 1920s. Why is AM radio in a band at 550 kilohertz to 1,700 kilohertz, while FM radio is in a band at 88 to 108 megahertz? It is all completely arbitrary, and a lot of it has to do with history.ĪM radio has been around a lot longer than FM radio. This renowned analyzer is easy-to-use, highly versatile, and allows you to connect to your personal computer. That’s why they developed the RigExpert antenna analyzer.
#RADI OBAND TUNER IMAGE INSTALL#
Whichever dipole you finally choose, install it as high as possible. Simply throw it up in the air and let the tuner worry about providing a low SWR for the transceiver. With a ladder line dipole, no pruning is necessary. Wire antennas fed with coaxial cable must be carefully trimmed to render the lowest SWR on each operating band. They enjoy the luxury of turning on the radio and jumping right on the air-without squinting at an antenna tuner’s SWR meter and twisting several knobs.Įven with all the hassles, you can’t beat a ladder-line fed dipole when it comes to sheer lack of complexity. After a year or two of playing tug o’ war with the wind, ladder line will often break.īesides, many hams don’t relish the idea of fiddling with an antenna tuner every time they change bands or frequencies. And ladder line doesn’t tolerate repeated flexing as well as coaxial cable. Unlike coax, you can’t bend and shape ladder line to accommodate your installation. You must keep it clear of large pieces of metal (a few inches at least). Ladder line isn’t as easy to install as coax. So why doesn’t everyone use the ladder line approach? The reason has much to do with convenience. Even so, this antenna is almost guaranteed to work well on several bands, despite the need to retune. You may discover that you cannot achieve an acceptable SWR on some bands, no matter how much you adjust the tuner. (You’ll definitely need to readjust it when you change bands.) (Anything below 2:1 is fine.) You’ll probably find that you need to readjust the tuner when you change frequencies. Just apply a signal at a low power level to the tuner and adjust the tuner controls until you achieve the lowest SWR reading. Ladder line offers extremely low RF loss on HF frequencies, even when the SWR is relatively high. Shorter versions will also work, but you may not be able to load them on every band. A 130-foot dipole of this type should be usable on almost every HF band. You can make this antenna yourself, or buy it premade if you’re short on time. Use regular coaxial cable between the antenna tuner and your radio. Feed the ladder line into your house, taking care to keep it from coming in contact with metal, and connect it to your tuner. You won’t be trimming or adding wire to this dipole.įeed the dipole in the center with 450- ohm ladder line (available from most ham dealers), and buy an antenna tuner with a balanced output.
Don’t worry about the total length of the antenna. These are going to be the two halves of your dipole antenna. Simply cut two equal lengths of stranded copper wire. You can also enjoy multiband performance without traps, coils, fans or other schemes.
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