# U Blox M8 not Working with Custom Constellation as Supposed **URL:** \ **Category:** Skydel Discussion\ **Created:** [June 14, 2022, 2:08pm UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665 "2022-06-14T14:08:24Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![mohdyaser](https://yyz2.discourse-cdn.com/flex030/user_avatar/learn.safran-navigation-timing.com/mohdyaser/32/422_2.png) [@mohdyaser](https://learn.safran-navigation-timing.com/u/mohdyaser)\ **Post date:** [June 14, 2022, 2:08pm UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665/1 "2022-06-14T14:08:24Z")
In the last weeks been trying to [Create LEO Constellation using this guide](https://www.orolia.com/document/creating-leo-constellations-with-skydel/?utm_source=hs-email&utm_medium=email&utm_campaign=skydel-community&utm_content=app-note&_hsenc=p2ANqtz-_UTumsZCqmQEx4oS7GpjyA4PLu-wykG64ZGxoMQ92GfQMuzs3z_zX6v8oAs6ZEDmz92_-8) The constellation finally looks fine (Check screenshot 1) , but the UBlox M8 receiver is unable to determine the position(Check screenshot 2); However in the mentioned guide, the receiver was able to lock to the four custom satellites and determine the position. Were you using a different generation? Am I doing something wrong? Please note when I use a GPS C/A signal the receiver and U Center works perfectly. ![screenshot 1](https://canada1.discourse-cdn.com/flex030/uploads/orolia/original/1X/e55d63436622190fba3e9e4ddf19483614cb1e61.jpeg) ![screenshot 2](https://canada1.discourse-cdn.com/flex030/uploads/orolia/original/1X/19efee98dcee98bb017243bb2cf5826e21f7f219.jpeg) Edit 1: I modified the simulation a bit and I got different results. I changed the Central Frequency from 2000 MHz (as written in the guide) to 1575.42 MHz (as GPS L1 C/A) and increased the gain to 60 dBm. The receiver was showing data, but it looks arbitrary to me, and still it was not able to determine the position (check the gif) ![receivers_not_working_properly](https://canada1.discourse-cdn.com/flex030/uploads/orolia/original/1X/65d70d88ebdc489113c2919cff22a6272739c3d0.gif) ---
**Author:** ![Grace](https://avatars.discourse-cdn.com/v4/letter/g/f17d59/32.png) [@Grace](https://learn.safran-navigation-timing.com/u/Grace)\ **Post date:** [June 15, 2022, 3:16pm UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665/2 "2022-06-15T15:16:37Z")
HI @mohdyaser, In fact in the first method (using the advanced jamming feature), there is no navigation message and ephemeris data in the generated IQ signals which are transmitted by the LEO satellites. So technically, the receiver cannot obtain a PVT and track a position. But you can still track LEO satellite information like you did in the video you post. If you want to get a PVT with the receiver, please follow the second method using the GALILEO constellation. With this approach, we just decrease the attitude of the satellites to put them in LEO orbit. The Ublox receiver may have certain doppler limitations, which could prevent it from having a PVT. But Skydel will always calculate them well. We understand that the application note was not very clear on certain points. But we updated it recently, I will email the PDF version to you. Regards ---
**Author:** ![mohdyaser](https://yyz2.discourse-cdn.com/flex030/user_avatar/learn.safran-navigation-timing.com/mohdyaser/32/422_2.png) [@mohdyaser](https://learn.safran-navigation-timing.com/u/mohdyaser)\ **Post date:** [June 16, 2022, 8:21am UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665/3 "2022-06-16T08:21:23Z")
Thank you @Grace I used the jamming method as it didn’t require custom signal unlike the second, and I couldn’t find any documentation or guide about custom signals. I would appreciate if you can refer me to any useful document. Also, if I use the Galileo constellation as LEO, can I increase the number of satellites to around 100 to simulate a real LEO constellation, or I’m gonna stuck with the Galileo satellites only? ---
**Author:** ![Grace](https://avatars.discourse-cdn.com/v4/letter/g/f17d59/32.png) [@Grace](https://learn.safran-navigation-timing.com/u/Grace)\ **Post date:** [June 16, 2022, 1:28pm UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665/4 "2022-06-16T13:28:09Z")
HI @mohdyaser, You make a good point about it. Yes, the number of satellites will unfortunately be limited to the number of GALILEO satellites. I emailed you the technical note for Custom Signal as well. Regards ---
**Author:** ![mohdyaser](https://yyz2.discourse-cdn.com/flex030/user_avatar/learn.safran-navigation-timing.com/mohdyaser/32/422_2.png) [@mohdyaser](https://learn.safran-navigation-timing.com/u/mohdyaser)\ **Post date:** [June 16, 2022, 2:47pm UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665/5 "2022-06-16T14:47:33Z")
Hi @Grace So isn’t there any workaround to have more LEO satellites? Also I didn’t receive your email, can you please confirm it was sent correctly. Thanks for your support!! ---
**Author:** ![Grace](https://avatars.discourse-cdn.com/v4/letter/g/f17d59/32.png) [@Grace](https://learn.safran-navigation-timing.com/u/Grace)\ **Post date:** [June 16, 2022, 3:22pm UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665/6 "2022-06-16T15:22:14Z")
> [@mohdyaser](#): > > So isn’t there any workaround to have more LEO satellites? You can use BeiDou constellation instead of Galileo. We have increased the number of PRNs to 63 for BeiDou constellation to comply with the ICD. This option will be available in a few weeks for the next Skydel release, but currently the maximum PRN is 35. I sent it back to you. Please let me know if you well received it. ---
**Author:** ![mohdyaser](https://yyz2.discourse-cdn.com/flex030/user_avatar/learn.safran-navigation-timing.com/mohdyaser/32/422_2.png) [@mohdyaser](https://learn.safran-navigation-timing.com/u/mohdyaser)\ **Post date:** [June 17, 2022, 10:01am UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665/7 "2022-06-17T10:01:54Z")
Hello @Grace I see… However, is it possible to use the two constellations together as LEO? because galileo and beidou would offer around 100 satellites which is exactly what we need. Also yes, I received the email! ---
**Author:** ![Grace](https://avatars.discourse-cdn.com/v4/letter/g/f17d59/32.png) [@Grace](https://learn.safran-navigation-timing.com/u/Grace)\ **Post date:** [June 17, 2022, 2:48pm UTC](https://learn.safran-navigation-timing.com/t/u-blox-m8-not-working-with-custom-constellation-as-supposed/665/8 "2022-06-17T14:48:18Z")
Hi @mohdyaser , Yes it’s possible. Regards