It may not help to run direct to battery. My mobile in my RAM 6.7 Cummins picks up electrical noise generated from either the electric fuel pump or the manifold heater element.. Not sure which one is causing it yet. It's not really annoying but you can hear it when it cycles on/off.. My mobile is ran direct to one of the batteries and yea, i checked with two different mobiles and both radios pick it up..
Bigger cities, i.e. Los Angles basin will drive you nuts.. Rural areas like Palmdale, Lancaster, Mojave Desert etc is always quite... hReally depends where your at.. I'm sitting at Lake Isabelle today and it's fairly busy with boaters and campers.. They aren't chit chatting to shot the breeze but rather sharing fishing results, camping locations etc..
if you have a 3D Printer there are tons of free files for cable clips in all sizes available on-line. Print them with ABS fillimant for UV protection.. They print failry fast and the various options will suite any need..
FYI,, After running a 'report' this morning for current updates.. it does look like many of the Repeater Linking guys are turning off 'Access Request' for their repeater sites. Meaning they are not accepting request to join their repeater circus.. Also noting that many are toggling from 'Paid Access' to 'Permission Required or Open System'.. Some are even disabling their rogue repeater.
Southern and northern Calif is extremely busy with CB like Chatter on every channel. . Bay area is just as bad. North from Palmdale gets pretty quite and some of the repeaters are actually a pleasant to use. . One of my favorite repeaters on El Paso Mtn can talk from Acton to Lone Pine and Hesperia and Lone Pine about 175-180 miles. Los Angeles basin has it's share of 'Spanish speaking guys as well and yes they can talk like two little girls in a powder room.
get yourself a Nano VNA.. They're great for checking Coax, Antennas and other things.. Lots of various how to videos on Google.. https://www.amazon.com/AURSINC-NanoVNA-H-Vector-Network-Analyzer/dp/B07Z5VY7B6/ref=sr_1_1_sspa?crid=27K9G2O94D6NI&dib=eyJ2IjoiMSJ9._c0Hx-JK1n0L41oe77KD7fcLIRsFX4_XZT_H7ZxdIs8BCuulklYWSZi7bTrGHD8BF5z2nq9d8KApRHbUSVwUAgta_Ua95QfM8DPnc4-tA2DhuxMPbV3MIXo2Mx5sF585EG8W2sSQ6wvgY9C8-kgPsGcS3mn3b6tKW01ocBWjju-1rDEXX_kIkdR_YyEidg6hl9HR8HPx1PGcYOS141bEaHxJBpwGmQ8UPK5D1Dd7bYc.oIILvBvlLqcs08bDNYLGdvdRu9BbUXTzf5XOjxbRaKo&dib_tag=se&keywords=vna&qid=1725726595&sprefix=vna%2Caps%2C164&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1