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something happened..


cbrown038
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Hey guys,

 

Im pretty new and have a question.  I installed a 50X in my pickup truck about a week ago. I also have a BTech V1 which I set up around the same time. After a little research and fiddling with them, Igot them both on a local repeater.. transmitting and receiving

 

Then, I was under my hood straightening up some of the wiring and cleaning things up, but immediately after, my mobil unit (50X) isn't transmitting. I can hear repeater traffic, but can no longer transmit.  I didn't change anything on the radio..

 

??  any ideas what may have happened?

 

TIA

 

Chris

 

WRKI386

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The radio is mounted under steering column and hard wired to the battery. Im using a nagoya UT 72 magmount on rooftop of my truck.  

 

Im noticing that when I try to transmit, the mic gain meter seems to jump all over the place, even when Im keeping a very monotone voice...

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I checked all the connections and they are secure.  Im obviously learning here, but the radio will transmit fine on GMRS channels, but not on the assigned repeater channel..  Does this indicate a setting is incorrect since it still transmits on GMRS simplex only, or could it be the radio is bad?

 

Also, the mag mount antenna plugs straight into the radio.. is it grounded properly just by plugging straight into the radio? I saw a description that said the UT 72 needs a ground plane.. which i assume is when the magnetic base is secure on the rooftop.. if not, how do you achieve a proper ground plane?

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Get a NanoVNA v2, a dummy load and test every segment of cable in the system, measure for impedance, if any given segment of cable is not 50 ohms (or close to it ) then its time to buy better cable, test every connector as well. I learned this the hard way, so now I only buy USA made Harbor Industries RG400, with MILSPEC silver plated N-connectors or Mini-UHF (since all my gear is Motorola) for short patches, and for mobile operation. Quality RG400 (or RG142 if you plan on permanent install) cables that are properly made will have impedance well within 1 Ohm of 50 ohms, at any frequency in the UHF range, will vary slightly depending on the length of the cable) 

 

You can measure adapters with a dummy load and NanoVNA... Measure the dummy load impedance directly, then place the adapter between NanoVNA and the dummy load, if the impedance changes by more than 1 Ohm, time to buy a better adapter. I recommend silver plated, and/or trimetal adapters only, nothing with chrome. And before I forget, don't expect PL259 to hold 50 Ohm impedance above 300 Mhz, they are severely lacking above 200 Mhz, so my advice, ditch the PL259 stuff, and go with N.... otherwise, the impedance mismatch will thwart any chances of having a decent system.

 

G.

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