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Antenna cable length
13vadimka13 asked 2 years ago
Hello, everyone! Happy new year! My receiver: Starter Kit Simplertk2b v1.1. I want to short antenna cable from standart 5 m to 10 cm. My aims: land survey in RTK, PPK, PPP, static mode and accuracy 10 cm regarding ground control marks. Reason of shorting: antanna and board in one case, near 3 cm between its. Is it real? If yes, what minimal length it must be? What features in U-center I must change to adjust receiver for my accuracy aims? At this time, cable is surounding the board.
1 Answers
13vadimka13 answered 2 years ago
I shortened the cable to 20 cm ANN MB antenna. Nothing has changed, everything is working well
AlphabetaCan you explain what you did to shorten the cable and how did you rejoin it?
Thank you
13vadimka13I cut cable by cutting pliers, soldered its to board to pins in other side of SMA female connector. After that I pinned the cable to board by plastic screed
You can see photo: https://drive.google.com/drive/folders/1Wx7Wy2jK93JOrcMDV9kBAkA8kmzJP2j-?usp=sharing
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replied 2 years ago
I wouldn’t hack up an ANN-MB, find an L1/L2 with a TNC connector, and get a short pig-tail SMA-to-TNC. A Right-Angle SMA would fit into tighter spaces.
Something equivalent to:
https://www.amazon.com/pigtail-wireless-router-Quality-Shipping/dp/B01CWJ4SSQ
You don’t need to adjust the receiver, it is measuring the signal as it arrives at the phase-center of the antenna. The cable length skews time a little, not the position. For short cables don’t have super-high gain antennas (ie look for 10-20 dB rather than 30-40 dB)
replied 2 years ago
Clive1, Hello! Thank you for answer! In this U-blox manual for ANN-MB: https://www.u-blox.com/sites/default/files/products/documents/GNSS-Antennas_AppNote_%28UBX-15030289%29.pdf write that “The use of an active antenna is always advisable if the RF cable length between the receiver and
antenna exceeds about 10 cm. Care should be taken that the gain of the LNA inside the antenna does
not lead to an overload condition at the receiver. For receivers that also work with passive antennas
an antenna LNA gain of 15 dB is usually sufficient, even for cable lengths up to 5 m. There is no need
for the antenna LNA gain to exceed 26 dB for use with u-blox receivers (at the RF input). With shorter
cables and a gain above 35 dB, an overload condition might occur on some receivers.” As I understand it, I can shorten it to 10 cm. If there is an overload, will the receiver be damaged? If there’s a protection from overloading the signal?
replied 2 years ago
I won’t hack up ANN-MB, because I may to cut cable and establish new SMA.