Advice on an A/B switch

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DJ11DLN

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Thinking of installing a TRX-2 in my car and feeding it with a Larsen NMO-150/450/800. I have this antenna on my pickup and it works very well. I also use it with my FD radios for VHF-Hi and 800 MHz. But if I mount the main unit under the back seat, which is the current plan, I won't be able to just disconnect it from the scanner and plug it into my H-T's when I need the extra range, as I do presently with my handheld scanners. So I am wondering if there is an A/B switch with enough isolation to keep my scanner from getting fried if I TX through it? Did a search and didn't find anything, might not have been worded properly, apologies if this has already been addressed.
 

chief21

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Most true A/B coax switches provide 50-60 dB of isolation, which should be more than enough to protect your scanner from damage when transmitting on your relatively low-power HT. Be sure to use an actual coax A/B switch and not some home-brewed double-pole electrical switch.

John
 

cmdrwill

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Most true A/B coax switches provide 50-60 dB of isolation, which should be more than enough to protect your scanner from damage when transmitting on your relatively low-power HT. Be sure to use an actual coax A/B switch and not some home-brewed double-pole electrical switch.

John
And NOT some hammy junk coax switch.
 

DJ11DLN

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And NOT some hammy junk coax switch.
Can you recommend a brand/model? I appreciate the replies (and no chief21 I wasn't going to try to "engineer" something on my own, LOL), but I'm looking for recommendations. If either of you know of a brand and model of switch that would protect against, say 25W output (just in case I should at some future point install a mobile in the car), I'd be interested to know what I should install. Or if you think this is just a bad idea and I shouldn't try to do it, I'll take a straight answer either way. Thanks.

EDIT: After using the 50-60 db figure to do a little Googling, I think I will just put a loop in the coax with a connector, all of which I can shove under the seat, and pull out to connect directly to the H-T if needed. I was hoping for an easier solution but this one seems safest. Thanks for your interest.
 
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DJ11DLN

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Why not just add another antenna? A 2m quarter-wave or small dual-band seems easier than switching coax connections frequently.

John
That definitely would be best solution. I was just hoping to avoid more holes in the roof. This is a POV in case I hadn't made that clear. So a second antenna is on the table and the switch idea is dead...but I'll have to think about it. It's not as if I have to have the extra range every day, just when we get a run into some of the fringe areas where a mobile does fine but an H-T with a duck struggles. The external antenna on my pickup makes a huge difference in those circumstances and this being an SUV with the roof a little closer to the ground but having a larger ground plane I'd expect similar performance. Thanks for the advice.
 
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