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Thanks, Jerry.? ?Our County had spent > $100,000 on our group to provide 14 go-boxes with Public Service Motorolla truked?radios as well as far less expensive ham radios....because the hurricane shelters are steel reinforced concrete buildings (schools) and the police handhelds simply won't get out. ..? With hundreds of people cooped p in a shelter....the police Need To Reach Backup if there is a disturbance...hence our ham radio group.

We were terrified of destroying one of those radios because large storage batteries can ALWAYS be misconnected with ring connectors to their bolt-terminals....and hence this project.? ?We built a couple of dozen AT LEAST when mosfets were still easily obtainable.? ?Now it is harder to find.? ? You want to arrange for very low series resistance because it means much much less heat dissipation.? ? ? When the mosfets get hot, their series resistance goes up -- BAD CYCLE!!

I have this on my 7300 and still a spare or two sitting around, so one will go on the sBitx.? ? We have them on every key radio in our Emergency Operations Center.? ?People under STRESS will make mistakes.? ? You could probabaly?build the same circuit with an N channel....if yu are willing to break the ground wire, which we didn't want to do.

This is something that can be built MUCH EASIER with SMD's which?are much more readily available.? ?But I don't have that ability to fool with.? ?Others could do it much more easily than I.

Gordon

On Mon, Sep 5, 2022 at 12:53 PM Jerry Gaffke via <jgaffke=[email protected]> wrote:

Correction for the final sentence:
?If the user does NOT fuse the battery with a fast blow fuse
of the appropriate current rating, then a reversed battery can destroy the rig.


On Mon, Sep 5, 2022 at 09:20 AM, Jerry Gaffke wrote:

If the user does fuse the battery with a fast blow fuse
of the appropriate current rating, then a reversed battery can destroy the rig.