Mar 21, 2014

Ham grab-box

At least part of the attraction of ham radio for me is the "shit done gone sideways" resilience of it. It's a (relatively) grid-independent way to communicate over a variety of distances when all else fails. I haven't looked into the longer-distance stuff yet - 10m and lower bands - but it will happen as time, funding, and space allow.

There are plenty of hams out there who build elaborate (and large) emergency communications boxes, that take up half the volume of their van and allow them to talk to God on simplex. Bully for them, but it's not something I'm interested in just yet.

A co-worker is a weather geek and goes stormchasing every spring and summer - without radio communications. While it's certainly possible to get a lot of the info via scanner, weather radio, and now smart phones, being able to tap directly into and participate in the SKYWarn 'nets is huge - especially if a storm starts taking down cell towers.

I'm planning to go chasing with him this year when our schedules line up, and wanted a VHF/UHF kit I could easily move from car to car. Beyond that, I wanted to be able to operate (at least briefly) without an external power source.

I already had a Yaesu FT-90R, Tram 1185 magnetic mount antenna, and a Vault VC-12 dry box. The next step? Adding a battery, some kind of external power, and shoehorning it all together. The VC-12 has internal dimensions of 11.75"W x 8.5"L x 4"D.

I did some digging for batteries, and ended up buying a 10Ah SLA via Gruber Power Services. It should be enough to run the radio for a couple hours of receive with minimal transmitting, can be installed in any direction, and most importantly will fit in the case.

But how to charge the battery? There is a West Mountain PG40 Powergate, which is a UPS circuit for 12V applications. It is, unfortunately, quite expensive ($140ish) and large. Reading through some forum posts, I found mention of the KI0BK Low-loss Powergate, which is much less expensive ($50), about half the size, and generally simpler. Done. Ordered. Add a cigar-plug cord and... steady power plus auto-swap to the battery if power is lost.

A fair number of hams will insist that an emergency box needs to be able to take power from an AC outlet... and I don't entirely disagree. But it wasn't in the cards for this particular setup; it would have added weight and complexity to the situation and seen very little use.

Next, how to connect the antenna? The radio is small but still cozy in the box. Much easier if the antenna just plugs in to the side of the case... so add a short patch cord and a bulkhead fitting, a bit of work with a 5/8" drill, and voila!

But that heavy battery ... that'll slide around if I'm not careful. So... I'll add a small L-bracket or two and some velcro, and I think that'll be set.

And the obligatory pictures:

 I've got a bit of work left to do - I need to fab a bracket for the radio, a mic hanger, and get the battery strapped down. I'm sort of considering swapping the FT-90 for the FT-7800 I also have, which has a detachable faceplate and is a bit easier to navigate through (and program), but is slightly larger. We shall see.


Old NFO said...

Nice creative solution to the problem Zer! :-)

Wolfman said...

For AC plug power, why not just include a 12V DC power pack? I've got one that's 1x2x2 1/2 and weighs abt two ounces, just a black box that the standard car accessory plugs into. That'd be easy enough to keep in the box, I think.

Laura said...

this is a really neat idea. hoping you get some good chases in this summer...and hoping y'all come out the other side without any damage to vehicle or persons.

ZerCool said...

Wolfman - mostly because of current draw. At idle it'd probably work fine, but at full power the FT-90 is drawing about 9A/12VDC - far more than a normal wall-wart can put out.

Wally said...

Love the setup, esp the portability given with the grab-n-go box.

Once I split ways with the pickup, that will leave me a FT90 to consider using for one of these.