Comms, how would one go about making that conversion? I have some of the same units - still functional with the original fifteen year old batteries, but I would like to keep them working...

Here is an Ebay source for both the strobe and conversion cap, you could contact the seller to see if they will sell just the cap:

NEW SDU-5/E Distress Strobe w/conversion cap for cr123

Pete

Thank you very much!

A conversion cap for using a pair of CR123 batteries
to power a SDU-5/E Distress Marker Strobe light can be found here

http://www.prc68.com/P/Prod.html#B

I have no experience with these - just Googled for it because the
question came up above.

They work great.

Any comments on how the PRC-90 Battery Adapter works?

No, but in my experience they have a good reputation, so I don't see why it wouldn't work. Military uses a lot of their stuff adapters for training and such, since they can use cheaper batteries for training.

Thanks Doug. I ordered the 90BAv3. I have an old PRC-90 and while it came with a functional battery on receive, I have no way of knowing how long it would last if I needed to transmit.

PRC90 is a pretty good basic emergency radio.

It transmits both voice and morse on 243.0 MHz (Int'l air distress & guard on every military UHF radio I've used) and also voice on 282.8 MHz (Joint/combined on-the-scene voice) aka SAR common. That combined with a PLB should provide pretty good comms; bring the outside world into range and then talk to it.

Just another hope-I-never-need-to-use-this piece of gear.

quite some time ago I purchased a brass cap fitting to convert my ACR Firefly (SDU5/e) from a mercury battery to CR123 this site. Works great.

Thanks for the info comms!! Very helpful to know. There's lots to consider but I agree, I don't want to use it in a way it's not intended for because it leaves more margin for error. I'm still on the fence about 1-way vs 2-way communication. Seems a combo of PLB and cell phone might be the best way to go.