Ron Lee wrote:
Ron Natalie wrote:

John R. Copeland wrote:
Antenna replaced? If it's broken, maybe.
Nothing in the upgrade itself would require that.
And if the cable works OK before the upgrade, it'll work OK afterward.

While the WAAS satellites use the same (L1) frequencies as the
others..rumor has it that the existing antennas Garmin sold with
the 530/430 have a hard time seeing low enough on the horizon to
meet the C146a specs.

I find that hard to believe. Do you know the elevation angle
requirement? I will check how low it picks up soon.

Ron,

As you know, the MOPS has gone through several revs, but my copy of
DO-229A specifies 10.-deg. They've released 229D and I believe it
hadn't changed between C and D, but the mask angle is now 5.-deg.

As an aside, remember the issues with some of the early 129 boxes? As I
recall, there was no specific requirement for any particular mask
angle. 7.5-deg (then 5.0-deg in a later version) was the recommended
value. Basically, as long as the rcvr. manuf. could prove that
Integrity was being maintained, it didn't really matter what mask angle
was chosen...

But it did/does. Effects such as local multipath come into play at the
low angles.

When examining the Availbility/Integrity tradespace, those on the
conservative side would rather take the Availability hit in order to
maintain Integrity. Conservative in this context meaning 'safe' as
opposed to Right Wing

Ron Lee

Regards,
Jon