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Ham radio transmit max power

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Old 06-13-2018, 12:17 PM
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Default Ham radio transmit max power

I want to mount a ham radio on the top rack by the front and rear door meet, the right side will be 144/440 MHZ max 50 watts, the left side 7.0 - 28Mhz 100Watts
Question what is the max transmitter power I can use without doing damage to the cars computers
also how far should I have the ham antenna from the car antenna (gps&radio)
2018 Jeep Cherokee Latitude

Last edited by lew_jean; 06-15-2018 at 08:42 AM. Reason: clarification
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Old 06-13-2018, 02:58 PM
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Is there a question here?
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Old 06-13-2018, 03:32 PM
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I heard a pig use a radio once, but had to turn it off. Too much squealing.
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Old 06-14-2018, 10:06 PM
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If you have to ask, something is wrong. Do you realize you must have an FCC license to run a ham radio? You should have learned your power limits in order to pass the license test.
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Old 06-16-2018, 12:38 PM
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He's asking about the interaction with the vehicle computer. Has anybody ever heard of this being an issue?
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Old 06-16-2018, 02:29 PM
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Originally Posted by Jimbo Slice View Post
He's asking about the interaction with the vehicle computer. Has anybody ever heard of this being an issue?
He's edited the original post at least twice after folks responded. First iteration was "I want to mount a ham radio on the top rack by the front and rear door meet." This explains the first two responses.

Second iteration had that, plus a question about the maximum power output for amateur radio. That is the reason for BRM's response.

Now we have:
Originally Posted by lew_jean View Post
I want to mount a ham radio on the top rack by the front and rear door meet, the right side will be 144/440 MHZ max 50 watts, the left side 7.0 - 28Mhz 100Watts
Question what is the max transmitter power I can use without doing damage to the cars computers
also how far should I have the ham antenna from the car antenna (gps&radio)
2018 Jeep Cherokee Latitude
This is much, much better.
Unfortunately I can't answer it since I know nothing about the KLs
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Old 06-16-2018, 06:44 PM
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Originally Posted by lew_jean View Post
Question what is the max transmitter power I can use without doing damage to the cars computers

Best guess (I'm a radio engineer) is any legal amount should be good as long as you follow proper installation practices and use quality connectors and coax. Use a double-shielded coax. Never cut corners on coax, connectors, or antennas. This is the most critical component of your system.

Let me give you an example from my dim, distant past when I worked in a two-way radio shop. We had a customer come in needing repairs on his car phone (this was very early in the cellphone days, and the older IMTS car phones were still around.)

While the boss was doodling in the innards of the IMTS transmitter (needed a tune-up), I got to chatting with the customer. He was a ham operator, and was in the habit of running higher power than was legal. He told me about putting a new 1500 watt linear (10 meter) in his truck, which was a Toyota extended cab. He had 4 car batteries in series behind his set in the 'extended' area, just to power his linear. The first time he fired it up, he killed his engine due to RF overloading his computer. He replaced all his coax with double-shielded and didn't have any more problems.


Originally Posted by lew_jean View Post
also how far should I have the ham antenna from the car antenna (gps&radio)
2018 Jeep Cherokee Latitude
As far as possible. While you have lots of frequency separation, you are also pumping out lots of power, and you may get enough coupling into the receive antenna to desense either receiver, possibly even ruin them. The GPS signal is pretty weak, and it's a wideband receiver, so it's pretty easy to overload it.
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Old 06-18-2018, 02:25 PM
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thank you for your comments

I will be doing the install later on this year when the temp is cooler

73'
Lew
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Old 06-18-2018, 08:09 PM
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Originally Posted by lew_jean View Post
I will be doing the install later on this year when the temp is cooler
You are wise, grasshopper!

We hit 100 today. I passed on running down an electrical problem in my truck.
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