Do I need an attenuator when I get close to the transmitter?

No, unless the emitter being tracked is located close to other transmitters which would overload the RF summer. The RF summer design is broad band and has a high dynamic range, but it is possible to overload it when the direction finder is close to high power broadcast stations. It is necessary to attenuate the signal at the antenna side of the RF summer, not between the summer and the receiver, so four attenuators must be used. On our current models, we provide a built in attenuator feature. The front panel has an ATTEN button that disables the preamplifiers in the RF summer thereby attenuating the signal by about 24 dB.