The only shielding issues you'd need to worry about are metallic objects and carbon fiber. Everything else we use is radio transparent.

Thanks, Warren - I'll proceed with the plan as drafted.

One point to add, keep the GPS transmitter as far as possible from the deployment electronics. Quite a few altimeters are sensitive to RF and have a tendency to fire their charges when the transmitter is turned on.

In my tests with Mike Konshak on the DC20, we found the older Missileworks RRC2 had an issue since it had no ground plane. The PF MAWD in mine seemed to be OK. Discussions with Adrian suggest the Raven is OK as well.

However, it's very cheap insurance to just line the inside of your avbay with aluminum or copper tape and make a little faraday cage. Mike had no issues after that.

-Ken

Thanks, guys - I'd seen reference to that premature ejection problem in scanning old posts - in fact,, a reference to carbon fiber shielding is some of those posts prompted my question about the encapsulating foam.

Good idea, Ken - even though I have 40"+ separating nose cone (dog collar) and av-bay, it is cheap insurance. I'll put that in the construction plan.

As I've flown multiple rockets with each and a DC-30 or DC-40.

I've yet to stuff the dog collar and the altimeter in the nosecone though...

I've used a DC-20 adjacent to RRC2 Mini's and a Raven and not had ill effects. I did test it though before hand.

Edward

I had my rocket eject on the pad this weekend, Nov 3. Not quite Konshak style, it was vertical on the pad before I armed the altimeters, and it sat there happily for at least 15 minutes waiting for two other flights, one of which involved a CATO motor still burning when it hit the ground. We were all walking back from making sure there was no further fire when BLAM, my rocket pukes its nose and main onto the ground.

I was flying Raven2 and an RRC2-mini.

I had my DC-30 collar about 12 inches away from my altimeters, although I did have pair of wires from the Raven that were quite a bit closer than that. The RRC2-mini was on its own battery, no shared ground. The Raven had some interesting data, but never fired its charges. RRC2-mini was definitely the culprit, I was able to set it off on the bench this afternoon.

TEST TEST TEST, and then shield anyway with Garmin collars. 3 watts is a pretty good bit of transmit power. I'm just glad I learned this (had only read about it before) lesson while it was still on the pad. Would have been pretty bad news if the exact same thing had happened 10 feet off the pad, then all my stuff would have crashed and the 6-second burn K375 would have had a pretty good chance to start a major fire. As it is I only have a beat up nose cone tip and a bruised ego, since I was quite aware of the problem but decided that my collar was "far enough" away from the electronics bay.

I'll be back sometime in the winter, with shielding and sans Missileworks.

-Bryan

Did you have your electronics shielded?

Edward

Really easy to shield, aluminum foil on the bulk plate or bulk plates between the DC and the altimeters. You also want to make sure all wires are twisted to try to prevent any wires from becoming an antenna. I saw someone have the same problem, moved wires around and no more problem. It is hard to believe just managing your wires and keeping them neat and organized and preventing wires from becoming antennas can help prevent this from happening.

When I flew I had everything shielded, and wrapped the ejection charge wires in aluminum foil. I would do this before you drop the altimeter - backups are good to have.

Edward

One thing I've done in almost all my dual altimeter birds is to build a common power bus (usually two or more 9V batteries in parallel) and to tie the grounds from both altimeters together. I don't use a common power switch, but all electronics shares the same ground and Vcc.

I wonder whether using shielded twisted pair wire would be a good thing on the e-matches with the shield bonded to the common ground.