Hello dear CalGnome client,

I am trying to get in touch with you because I have identified a problem with the CalGnome program which I would like to fix soonest.

At this time, based on my notes about your order of the CalGnome and my fulfilment, I cannot see whether or not you are using a LX7/8/9nnn with built-in FLARM as source for the FLARM data stream feeding the CalGnome.

If that is NOT the case, then you may disregard this article altogether.

If, however, you run such a configuration in your plane (or plan to run such a configuration after a future instrument panel rebuilt), your CalGnome will/would not be able to work as designed.


LX7/8/9nnn devices are not 100% compatible with original FLARM devices; they do not emulate the FLARM data stream completely. One NMEA data sentence is omitted. Instead, the LX sends proprietary data sentences. The CalGnome firmware is - was - dependent on that specific data sentence, as the flight altitude was derived from that very sentence.

Four years ago, when the CalGnome development was in its final stage, LX-Red-Boxes and various other LX FLARM data sources were 100% compatible with the original FLARM, and they still are (Well, there is sort of a grey area with RedBoxes, some of them are 100% conform to the FLARM standard, others are not.  I do not know of any discriminator to decide that). This is why - apparently with too much naïvety - I assumed the newer LX7/8/9nnn devices to comply to that FLARM standard as well. As I learned recently - sadly so late -, they are not.
So far the bad news.

Now the good news :
Meanwhile, I have changed and updated the CalGnome firmware in such a way, that the program is not anymore dependent on that sentence. Altitude is now derived from other sentences in the data stream. The only "backlash" is, altitude precision is now in meters, not in feet as before. I am sure this does not hamper the usability of the CalGnome.

This is why I ask you to return the CalGnome to me. I would like to update the firmware of your CalGnome and return it to you - as soon as possible and at no extra cost. I suggest you get in contact with me first, so that we can arrange for a smooth update process, as I am not always at home and ready to react.

Some answers to obvious questions :

  • CalGnomes delivered later than Nov 8th 2018 do not require the update. Their firmware is up-to-date.
  • The update does not restrict the use of the Calgnome to LX devices. The CalGnome will continue to work with other FLARM data sources seemlessly.
  • Devices which are BEHIND the CalGnome in the FLARM data stream are not impeded by the update.

I sincerely apologize for the hassle this creates.


Horst Rupp


Version 8 ---- Copyright © 2008 - 2020  Horst Rupp