Hmm. I know this may hurt to hear, but sometimes the most expensive part of any truck is the antenna - because you have to replace them every time you leave a terminal, ATM - or deliver thru any low overhang...it's worse than fuel - you get scraped both ways, at the pump and inside at the counter...
SIGH...
Thanks for sharing that photo - it definitely helps...
You're doing fine - it's the best with what you have to work with and that's because of problems from more of an external (companies around you) issue.
What you have is the ideal location, just not survivable - and yes loading location of the antenna makes the biggest difference between a dummy load versus a real antenna.
Ok, do we have options on what kind of antenna - or are we kinda sorta' stuck with the Browning?
Outback bar? Forget it, it doesn't fit your needs...IT might but there are reasons against it right now mostly due to clearance...
Because you'd have to "adjust" height by raising and lowering the bar - so that Outback style may provide some relief - but then its really close clearance and tight spacing and if you haul heavy - you have to SLIDE your tandems as well as your hitch to make this road worthy - so that makes the front side (the rear of the cab) a clearance issue.
You have a good setup now, just sorry that the Browning is the one you GO-TO for the radio ... that's what makes this a hard effort And anyone whom has had a truck life like I did being a company boy / Gopher - you worked with what you had, which in most cases wasn't much.
It's like living in a dinghy and being parked in a trucks stop next to ocean liners...one cruises the highway - while the other bobs along with the waves...you had fewer options but you did make it work. You're dealing with a Cadillac and that can get costly when repairs have to be made...
Ok, here's (after doing the dishes) what I've come up with, I'm going to leave this with you because to make this work, the choices are up to you...
You may already know these things in this list, but I can't proceed without knowing what you can do or are willing to change - because right now at this moment - you're already at the ideal settings you can do and make it survivable.
One - Weight:
The lighter the antenna - the better off you are in an install on a single hole - like roofs. The mass of the antenna affects how much torque the whipping action will place on the mount - and the material around it.
Two - Wind Loading:
Ok, got a light antenna(s) - but if they are long - they catch a lot of wind. This adds in another type of force like torque but I call it shear - against the mount - and material around it.
Three - Antenna Load height:
We already know that height matters as well as placement for image and directionality - so higher the better but 13' 6" is pretty much the norm I have to work with and think about...so if Top load is possible - use it, but how far up? Again, 13' 6" is standard.
This doesn't always work for loading grains and weighing - they don't care what you use - they just want you to haul it - so again something to think about in regards to quality versus quantity - because you're going to go thru stuff faster due to their unwillingness to provide clearance - you may not have much of a choice but to keep it cheap when you deal with these farms.
A SECONDARY effect to Load height - goes to the First one - Weight. Top loads are top heavy - affecting balance which requires two things - good mounting practice and proper heavy duty spring / shock mount to handle the torque from that unbalanced antenna load whipping around up top after you hit something - damping using heavy springs and thicker mounts and bracket scenarios help with reducing torque effects.
Four - Antenna location:
Although Cowl mounts provide the best overall image and omnidirectionality - they are not the most durable nor voted Most Likely To Succeed - Succeed? Yes, but at making a mess out of your truck and roof. You may be stuck using the Mirror mounts for the longer CB antennas and use the upper cowl/roof mounts for scanner, satellite or Bluetooth communications.
So if you're looking for someone to agree I do, but unless you're willing to invest more into reinforcing the rooflines antenna mount - you will have to suffer a lower level of performance when it comes to granaries' that are archaic and haven't upgraded since the Wagon Wheel got replaced with Radial tires...
You have two things against you, rear panel flaring fariing clearance (rear of cab to front of trailer) and height clearance from the loading docks that don't care what you own - just haul it.
Otherwise you have everything else figured out - it's just complex because of the needs of the few that outweigh the abilities of the many that don't have to deal with the stuff you have to.
If by chance, you come across someone that has a good setup - like you want - grab a photo and share it here so we can help you put together something better like what you see others are doing.
:+> Andy <+: