My BMW R1150 GSAA at Deals' Gap

Powered by Squarespace

Entries in Maxrad ASP7795 antenna (1)


Power-output level "hack" for the ICOM F21GM GMRS Radio

As mentioned previously, I have an ICOM GMRS "handy-talkie" mounted in the Jesse top-box on the R1150GS Adventure. It's cabled to the AutoCom intercom and draws bike power (12 VDC) through a battery eliminator product CBE-210 from Batteries America.

On a whim, I checked to make sure I had the radio set to transmit at the highest possible power (4 watts) since I have it cabled to a permanently mounted Antenna Specialists/PCTEL ASP7795 3dB gain UHF antenna on the top of the Jesse top-box. The ICOM user guide provides a procedure that requires you to push a sequence of buttons and listen for a series of beeps to confirm that the setting change was made. Well, no luck. It seemed to be stuck permanently on the low (1 Watt) output level.

ICOM F21GM GMRS RadioI removed the radio from the bike where it would be easier to work on and in the process, found that using the ICOM-supplied BP-222N Ni-Cd battery pack instead of the battery eliminator, I had no problem adjusting the output power between the 3 levels using the procedure described in the user guide. WTF?

There must be some way the radio can tell the difference between one battery pack and another.

Here's the radio and the CBE-210 battery eliminator:

And here's the radio with the BP-222N Ni-Cd battery pack:

They look pretty much the same on the inside, don't they?

I figured it had something to do with that small spot of exposed metal in the middle of the battery back and that small "push button" switch on the radio itself, but wasn't sure - yet.

Now, here's yet a 3rd picture. This time, it's the radio with ICOM's alkaline battery pack that allows AA batteries (6) to be used for power.

Note the lack of the exposed metal patch on the battery pack. Hmmm, getting warmer.

Since there's no way that alkaline pack would support 4 watt transmit for very long, I surmised that the metal patch (or lack of it) had some influence on the telling the radio it could be programmed to mid or high power settings.

I did some quick checks with my trusty multi-meter and determined that there was continuity between the metal patch and the Negative connection on the Ni-Cd battery pack from ICOM. Ah-ha! The CBE-210 from Batteries America "looks" the same, but there's no similar continuity. Bummer!

I bet the fine folks at Batteries America didn't know the F21GM uses this connection (other ICOM radios sold to the amateur radio community don't so it doesn't matter - IC-V82 and IC-U82 models in particular).

More testing with the meter revealed that the Negative battery connection was actually connected directly to the metal chassis within the radio when the battery was snapped in place. I also determined that what I originally thought was a "push button" switch on the radio was actually just a spring-loaded contact designed to press (and keep pressing) against that metal patch on the battery.

The Hack:

I determined that that little spring-loaded contact just needed to be kept "in contact" with the Negative/ground provided by the battery. Since that Negative connection was actually connected to the radio's chassis I figured a small piece of aluminum foil folded a few times for extra thickness and placed over the contact would do the trick.

The picture above shows the foil before I added a small piece of clear packing tape over it to keep it in place. Miles later, the radio's still happily transmitting at the 4 Watt (highest) level and I'm a happy camper. Problem solved.

Ed Gray's made the same modification to his radio and also continues to be happy with the results.