# Postcard RTK: Fix instability at speed **URL:** \ **Category:** GPS/GNSS\ **Created:** [May 25, 2026, 6:34pm UTC](https://community.sparkfun.com/t/postcard-rtk-fix-instability-at-speed/68838 "2026-05-25T18:34:56Z")\ **Posts on this page:** 1\ **Showing post:** 22
**Author:** ![bamarcant](https://yyz1.discourse-cdn.com/sparkfun/user_avatar/community.sparkfun.com/bamarcant/32/9152_2.png) [@bamarcant](https://community.sparkfun.com/u/bamarcant)\ **Post date:** [July 8, 2026, 5:37pm UTC](https://community.sparkfun.com/t/postcard-rtk-fix-instability-at-speed/68838/22 "2026-07-08T17:37:24Z")
Yea,the solution is to have a dedicated port for corrections, you could use a[module](https://www.sparkfun.com/sparkfun-bluesmirf-v2-jst.html) on the third port… As for the dynamics, I also confirm that the fix is lost during even slight changes of direction… > [@PaulZC](#): > > …it does not have a dynamic model setting… (IMHO) Quectel did not implement a motion variile because the [kisilicon](https://community.sparkfun.com/t/sparkfun-gnss-flex-phat-lg290p-some-of-the-ppp-features-not-supported/66349/7) chip ([LG290P](https://kisilicon.com/productinfo/111312.html)) was not designed to process hight motion dynamics;(_perhaps deliberately by the creator so as not to allow for military purposes_). Regards --- _[View the full topic](https://community.sparkfun.com/t/postcard-rtk-fix-instability-at-speed/68838)._