Well, i’m coming late to this dance, a shame, because I love these toys.
The cobra 29LTD has been the big truckers gold standard for decades. It’s a very good radio, and it’s durable. I actually have 3, and one is a 29 Ltd night watch like yours, but the night watch part of it is inconsistent across the face. They had a lot of trouble with that when they came out with it, but it doesn’t affect the performance of the radio at all.
If you got it for free, it might be worth taking it to a truckstop radio shop and just asking them to check it. Sometimes they’ll do it for free, sometimes it’s $15 or $20, but it’s money well spent because it will put you dead on track for what you have to do to build a good system.
On my personal trucks, 96 F250 diesel four-wheel-drive, 97 Ranger, and an 87 Ranger, I mounted the radios between the sun shades above the mirror. The roof is a double sheet metal with a space between them above the headliner, if you’ve got a headliner.
I usually make a relatively square 1/8” aluminum plate, not wider than the CB bracket, and I screw it to the inner sheet metal panel with some self taping screws in each corner. You can hang a Virginia ham off it. I put the CB bracket on it with a couple small nuts and bolts before I mount it to the ceiling.
To locate it, I push it as far forward as it will go with the antenna wire and the power wire attached. When it’s up there, you don’t want it tilting upwards, you want it to sit level so you can see it. I love that location because it’s just a quick flick of the eyes to see the knobs and what’s going on, and I personally believe it’s infinitely more accessible to adjust things or change channels.
I put my mic clip on the right side of the radio, and I can take the mic on and off without even taking my eyes off the road.
The final benefit is that the speaker is pointing down right next to your ear
The 102 inch whip with a 6 inch barrel spring is apparently exactly 1/4 wavelength, and for a mobile unit, it puts out the cleanest signal and has the best receive length.
Shorter antennas usually have some of the element wrapped or they have a coil installed at the bottom or the top to give it the proper electronic whatever to send out the best signal possible from a shorter antenna. Default, since they’re shorter, you don’t get the same output or receipt.
For mounting location, you have to think a little bit about what you’re going to use it for. Over the years I’ve used mine for pretty much two things. If I’m someplace where I’m unfamiliar and I’m looking for something, you can call out and say, does anybody know where such as such is. That’s not as necessary these days with smart phones. My other use was just chatting with whoever was driving down the road when I was on long trips. It keeps you crisp and it keeps you awake. I talk to drivers or the truckers or whomever, and they’re usually willing to chat for the exact same reason.
Since I need it to perform best on long highway trips, I ended up mounting it on the driver side bedside, between the rear wheel well and the tail light. I mounted the ball about halfway from the bottom to the top. With the 102 inch with the 6 inch barrel spring, that leaves about 7 feet of the antenna clear above the bed. It’s far enough away from the cab that the interference from the cab is greatly reduced, as opposed to mounting it close to the cab or on the toolbox.
When I mount the ball, I tilt the antenna inward just about an inch, and I tilt it forward about an inch or inch and a half, so at rest it’s tilting a little bit towards the passenger seat in the front. When you go down the road with a whip, it will bend backwards, which will give you best performance.
I usually also mount a plastic plate on the top of the bed that reaches out enough to touch the antenna, horizontally. If it’s plastic, I drill a couple holes in it, and I run a small zip tie around the antenna. Having that second secure location above the main mount really keeps the antenna standing straight. I always use a very thin zip tie so if I hit a tree branch or such, the zip tie just pops and the antenna lays over, no damage.
If you have to go someplace with a low overhead, you can simply loop a bungee cord around the antenna and hook it to one of the holes in the bed. You can still broadcast while you’re doing that, but the signal will be weaker, but that way you don’t damage the antenna or knock a sprinkler head off in a parking garage
I mount mine on the driver side so that when I’m driving down narrow streets or I have to park, the antenna is furthest from the curb so it’s not banging into tree branches, signs and such.
It’s my understanding, the ideal cable length between the radio and the antenna is 18 feet which is 1/2 wavelength. That’s usually longer than you need, but you’re not supposed to coil up the extra. You’re supposed to lay it back-and-forth irregularly or do a single run up and back rather than coil it. If you coil it, it can act like a transformer loop, and affect the signal.
97 extended cab. I have code 3 lights and other accessories, hence the switch panel. That switch panel also helps the radio sit flat and easy to see. cobra 29LTD nightwatch
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97 mounted before sides
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87 antennae location
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F250 antennae location
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That F250 has a fiberglass cap, so the only interference is from the bed, not the cap
I know you said you did yours already, but if you’re like me, you’ll change it around from time to time. I’ve used a similar set up on trucks for 40 or more years, and they always work pretty well.
The 97 has double antennas that are mounted just behind the cab at the level of the door handle, with 6 foot sticks. They’re too close together, so I only have one of them connected. From that location, about 4 feet of the antenna is clear of the truck cab.
87, fewer features, so fewer switches.
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Hope it helps