I have been checking out today the receiver I intend to use for the NB transponder. This uses an EME quality preamp (ca 0.5dB noise figure) at the feed with coax feed to the downconverter at the back of the dish. The feed is a simple 22mm copper pipe squeezed down at one end to fit inside a WG16/WR90 waveguide flange.
I have two preamps available, from DU3BC and F1OPA. They perform very similarly on EME, but I wanted to check first their gain response at 10.706GHz, since they both use internal bandpass filters. The results are given below. The DU3BC has slightly higher gain and was selected for initial tests.
The downconverter is an old WDG002 design, which has a two stage preamp (tuned for 10368) and a pipe cap type image filter (tuned to 10488). Performance at 10706 is degraded compared to 10488, mainly due to the attenuation of the image filter at 10706. LO injection is at 2586MHz from an LMX2326 synthesiser, locked to 10MHz.
Even though it is operating well above 10488, good signals were received from the 10706 beacon at an IF frequency of 362MHz - screen capture from HDSDR is attached.