Differences

This shows you the differences between two versions of the page.

--- 1296mhzfeed [2026/05/17 23:07] – [1296 MHz Feed] dsheen
+++ 1296mhzfeed [2026/08/22 14:42] (current) – [Control Interface] dsheen
@@ Line 13: / Line 13: @@
 The 1296 MHz feed borrows version 2 of the [[https://github.mit.edu/w1xm/Antenna_Base_Switching_Board|W1XM Control Board Design]] by Noah Haefner (K9EA). This board provides regulated 12 V power for the LNA, as well as opto-coupled control of the LNA power and TX/RX relay coil.
-Currently, we have replaced R6 and R11 with 510 Ohm resistors to make the board controllable by the 3.3 V GPIO pins of the Ettus USRP X300 SDR. Measurements indicate that this modification causes the RX_EN pin to draw around 2 mA from the Ettus's GPIO, which is within the safe 5 mA limit specified by Ettus. The board itself provides opto-isolation and has FETs which switch the higher currents for powering the LNA and relay coil.
+R6 and R11 were initially replaced with 510 Ohm resistors to make the board controllable by the 3.3 V GPIO pins of the Ettus USRP X300 SDR. These have since been put in series with a 10k resistor (currently jumping the feed connector) since it is running on 26V again.
+Like the rest of W1XM, the default state of the LNA protection relay at the feed is the transmit state (in which the LNA input is isolated from the feed). To be able to receive, the bigdish sequencer MUST be in the receive state. this can be achieved by logging in through the UI program provided with the client library [[https://github.mit.edu/w1xm/BigDish_Sequencing/tree/main/client|status_window.py]]
-Similar to how the board is used for the rest of W1XM, the relay is configured such that it is in the transmit path by default (when unpowered). Putting 3.3 V across the RX_EN_P and RX_EN_N pair switches the relay into the RX path and turns on the LNA. This configuration decreases the probability of accidentally having the LNA in the RF path when transmitting and destroying the LNA.