I guess that is one advantage of not having a box in the panel 
I have written to uAvionix and asked about their products, since that is my “box”, will let you know once they reply.
Here are some GPS simulators:
https://www.orolia.com/products-services/gnss-simulation/gpsgnss-simulators
I guess one could find some cheaper-not-so-legal version on eBay as long as it is run in a shielded chamber.
Peter wrote:
Unless it is still made or supported (i.e. Garmin or Avidyne) then good luck with that…
It doesn’t necessarily mean mean you’re safe. You remember the story of Diamond and their support for early (years 2006 and 2007) G1000 equipped aircrafts. It has been few years from last firmware update for these devices (version 9.x while actual version is 15.x) and you can easily find yourself in situation that 20 years passed and you’re affected with this bug.
Yes it is a great piece of luck that the two cases (that I know about) of avionics which
were produced by companies which
Perhaps a Venn diagram would have worked better 
In the case of Diamond it would have been a huge problem if instead of the G1000 they had chosen e.g. an Avidyne product (containing a GPS; back then no Avidyne panel mount box did, AFAIK) because even though Avidyne would have fixed the bug promptly, Diamond might have not played ball on the firmware update. Desperate owners might have used some reverse engineering methods; some of the G1000 functionality can be expanded with “keys” from interesting sources, but they are expensive.
I wonder, what about Aspen? They have no OEM installations AFAIK so can be user-upgraded (well, by an avionics shop in most cases).
I couldn’t call this a ‘bug’ as the Navstar system was designed with this in mind.
Given the original design and development limitations imposed at the time, this was an excellent tradeoff for the purposes intended.
Also, they wanted to shut GPS down and replace it, but the public wouldn’t let them…
So, we’re all just lucky they let us use it, until our nav systems stop working.
Hope it goes well Peter. One more chapter to your amazing AC ownership book.
Who needs dark hair anyway? Grey is all the rage for kids now…
The bug is not the system per se (where I agree it has been a rational design choice at that time not to waste too many bits to differentiate two bites that are hard to confuse in the first place).
The Bug is how some manufacturers used that info in an unsafe way in their software for purposes it has never been intended to use (e.g. checking the validity of a nav data base). Using information for different purposes or in different ways as it was intended is one of the most common pitfalls in software engineering – it seems that Garmin is doing a much better job than Avidyne in that respect (but can also be pure luck that Garmin is not affected).
I don’t understand how this stupid bug got in. Any programmer who knows what a 0 or 1 is will know the biggest unsigned number which can be represented with 10 (ten) of these, and it is 1023, and since a GPS gives you UTC date+time, why not just use that for database or whatever expiry purposes?
I wonder if perhaps the problem is with a bought-in module. For example the KLN boxes from King use a module they got from a specialist GPS receiver module manufacturer.
I agree it is not a GPS bug at all. It is a cockup at the receiver end.
