8th January 2009 DEEP Impact / EPOXI is down linking a very strong signal from its 8434.1203MHz transmitter as can be seen below;
The TWTA draws 54 Watts during transmission, with an RF output averaging 42.6 dBm (18.2 W). The LGA is composed of two coupled hemispherical microstrip patches radiating in opposite directions, +Y and –Y, providing a near-omnidirectional antenna pattern. Each of the two elements includes a receive patch and a transmit patch. The receive patches and the transmit patches are each connected via 3-dB couplers. The LGA system has a receive gain and transmit gain of approximately 3 dBi in the +Y and the –Y directions. The HGA is a 1-m-diameter parabolic dish antenna providing 35.6 dBic gain and 2.36° beamwidth at 8.435 GHz for the downlink, and at least 34.25 dB and a 2.76° beamwidth at 7.179 GHz for the uplink.
This is the block diagram of the telecommunications subsystem onboard EPOXI;
An excellent technical document on EPOXI telecommunications can be found here