 click for larger image (28KB)  click for larger image (52KB)  click for larger image (44KB) |
To improve receive performance, an Angle Linear RF Assembly is installed between the duplexer and the receiver (Thanks to Chip, N6CA for providing the assembly). This assembly consists of two quarter wavelength cavity filters followed by a PHEMT preamplifier. The photos to the left show different views of the RF assembly. The two cavities provide the supplementary filtering required prior to the preamplifier. The PHEMT preamplifer improves overall receiver sensitivity by providing a low noise, high gain stage prior to the receiver. Performance characteristics of the RF assembly are shown below. |
 click for larger image (40KB) |
This set of plots shows the close-in characteristics of the pair of cavity filters. Insertion loss and input return loss are plotted versus frequency. Note that the insertion loss for the filters is approximately 1.1 dB and that the return loss is a minimum of 19 dB over the entire repeater receive band. |
 click for larger image (32KB) |
This plot shows the out-of-band rejection of the filters, with particular attention paid to the rejection at the repeater transmit frequency (44.5 dB). |
 click for larger image (16KB) |
Shown are wideband plots of gain and noise figure for the PHEMT preamplifier. the receiver operating frequency, the noise figure is approximately 0.7 dB with a gain of 14 dB. |
 click for larger image (16KB) |
These plots show the combined close-in gain, noise figure and filtering performance of the RF Panel. |