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The Other Antenna
Maybe you've decided to use the 2.4 or 5.8GHz ISM bands to pass data back and forth to the transmitter site. If so I'm going to assume you're putting together a rugged system, and for that reason you would probably want to at least consider Andrew as your antenna maker. For the 2.4GHz band you could chose the 19T-2440F-1; it's only 15" in diameter and generates 19dBi of gain (make sure you adjust your transmitter TPO accordingly). For the 5.8GHz band one option would be the 23T-5800F-1.
Application 3: Remote broadcasting
Even with the recent proliferation of IP codecs there are still plenty of reasons to talk about the good old-fashioned 450MHz RPU systems.
Most man-made electrical noise is vertically polarized, as it turns out, and most users in the 450MHz RPU band use vertical polarity since it's just easier. However, if you want to minimize noise pickup and interference from other users, one of the best ways is to use horizontal polarity in your RPU system. Fortunately Marti makes a horizontal, omni-directional antenna that can be used as the base station antenna: the HA450. This antenna comes with 1, 2, 4 or 8 bays. Even at 450MHz the HA450-8 is big: the aperture is 14.5 feet. At the same time, it develops 8.5dB of gain over a dipole. On the transmit end you have lots of choices as well for an antenna, but at least consider the Marti YC series because it develops 10dB of gain, and can be physically oriented in either polarity.
Wireless microphones are a big part of many stations' remote broadcasts. What better way to mingle in the crowd? There isn't much you can do about the transmit antenna, since it hangs off the bottom of the handheld mic or is otherwise integrated. All you can really do to optimize performance of a wireless mic system is to increase the antenna gain on the receive antenna. (Avoid using the little antennas that come with the system when you buy it — that is if you want to get out more than about 50'.) Here you have quite a few options. Lectrosonics makes the ALP series. For example, the ALP620 covers the entire 450 to 850MHz band, with a gain over a dipole of 4dB. (Remember that the front-to-side and front-to-back ratios are high on a LPDA such as this; that helps mitigate interference and multi-path effects). Output impedance is 50 ohms. Some stations like to set up wireless systems so their jocks can go way, way out in the crowd, or maybe do spontaneous man-on-the-street segments in front of the station or at some other regular spot. In this event you may want to permanently install an antenna that points at that spot. Consider then something like the Kathrein/Scala CL1469B. This is a fairly large log-periodic antenna, made to be outdoors all of the time. It develops 8dB of gain over a dipole; 50 or 75 ohm versions are both available.
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Also in the March Issue
- The "And More" of Automation
- FCC Enforcement Items to Watch
- Testing AM Antennas
- New Products
- Field Report: Cloud Microphones Cloudlifter CL-1
- New Products at the 2014 NAB Show
- Side by Side: IP Codecs