It’s no secret that today’s environment is RF-heavy. Between cell phone traffic and various signals from the surrounding area, it’s a wonder that there is any space at all left for wireless audio to work in. Or, we might find free space, but the strength of our signal might be inconsistent or noisy.
It is tempting to amplify our RF on the receiving antenna side when we are not getting the desired signal. Instead, we need to look at balancing our signal to noise (S/N) ratio. We want our desired signal to be significantly stronger than background noise or interference but not so strong that it overloads the receiver. One way to control gain in congested RF environments is through an LPDA antenna (Log Periodic Dipole Array), also known as a shark fin, batwing or paddle antenna, such as our active/passive ALP690. LPDA antennas usually cover a wide range of frequencies yet have a directional pattern enabling us to reduce the impact of off-axis RF sources. LPDAs passively boost on-axis signals as well, which may also overload receiver inputs and/or bring up the RF noise floor. The ALP690 has a built-in amplifier with selectable gain and filtering so it can be set to boost or reduce the signal strength according to the gain structure needs of the system, largely dependent on the length and type of coax cable being used for the antenna run.
The ALP690 antenna is powered by DC bias inserted on the coaxial cable connected to the 50 ohm BNC jack. This power can be supplied by a Venue Series or DSQD receiver, an active multicoupler or an inline BIAST. When no bias is applied, the ALP690 automatically switches via relays to function as a passive antenna, so that the antenna can be used for receivers as well as IFB or IEM transmission applications. Please note that when powered, this antenna can only be used for receivers.