First, let me preface by emphasizing that the only way to really know is with a ground test. Go through a simulated flight and look at the real-time data (since the baro data isn't real in the simulation) and compare the results with and without the radio nearby. And importantly, do the testing with a setup that includes ematches connected you're planning to use, since those can act like antennas.

But with that said, I would be surprised if there were any interference. I fly with a Beeline transmitter literally in side-by-side with the Raven, with not a blip in the telemetry. This setup with a Parrot altimeter would put a big signal into the baro measurement for every transmission.

So has anyone ever done any testing with a DC20 or DC30 next to the raven with ematches attached? I'm thinking about making an AV bay with both devices next to eachother but wanted to check and see if it has been done before I conduct some testing of my own. Mike noted that if the altimeter has a ground plane then it is less susceptible to interference; Adrian, does the Raven have a ground plane and might this help to control it better with the transmitter nearby?

I have flown a Raven and a DC20 in the same bay several times but only to record data and not to deploy the parachute. Seems to record just fine but slightly scared if pyro charges are attached.

I found a copy of Mike's article:
http://www.apogeerockets.com/education/downloads/GPS_Recovery.pdf

This seems to give the impression that the premature deployment is most likely in barometric altimeters but since the Raven uses the accel during the boost phase this might also help the case.

Even if someone else has flown them together it is still best to ground test in flight configuration. Just hook up th ematches without the charges. Let it sit there for a while. I learned the hard way at mayhem. Had my charges go off on my rr2c mini while on pad. I did do a ground test but did not have them in the avbay the same way as I was for flight. Granted this was not with the garmin but with the telemetrum. Easily solved in my case by twisting wires on the advise of Bdale and Keith.

So has anyone ever done any testing with a DC20 or DC30 next to the raven with ematches attached? I'm thinking about making an AV bay with both devices next to eachother but wanted to check and see if it has been done before I conduct some testing of my own. Mike noted that if the altimeter has a ground plane then it is less susceptible to interference; Adrian, does the Raven have a ground plane and might this help to control it better with the transmitter nearby?

I have flown a Raven and a DC20 in the same bay several times but only to record data and not to deploy the parachute. Seems to record just fine but slightly scared if pyro charges are attached.

I found a copy of Mike's article:
http://www.apogeerockets.com/education/downloads/GPS_Recovery.pdf

This seems to give the impression that the premature deployment is most likely in barometric altimeters but since the Raven uses the accel during the boost phase this might also help the case.

Yes, the Raven has a ground plane. If you can't see any blips in the recorded data from the transmitter during ground tests, then it won't be affected in flight, either.