Use of Nagoya UT-72g with roof rack

[WRWM519]

I am new to GMRS, and recently acquired Nagoya antennas (771g and UT-72g) for improving reception on my HT. My question has to do with potential interference using the rooftop 72g on my station wagon which has a roof rack I use for kayaks and such. 

Should I anticipate that having the metal rack surrounding the antenna would absorb RF and attenuate reception?

Thanks in advance.

[Over2U]

Following…

[KAF6045]

On 3/20/2023 at 10:30 AM, WRWM519 said:

Should I anticipate that having the metal rack surrounding the antenna would absorb RF and attenuate reception?

Short of building a model in some antenna evaluation software (or putting the unit on a test range), anything goes.

My expectation is that it will "wobble" the horizontal pattern some, reducing it in some directions while extending it in others. There is a reason so many truckers used phased duals (left&right mirror mounts) for CB -- the pattern tends to extend in the direction of greatest metal mass, so with a big trailer behind, much of the signal went to the rear and the rest forward. The phased pair could help direct a bit more to the sides for a circular pattern (even free ways aren't completely straight).

[WRHS218]

I used that antenna on my Toyota SUV that has a heavy duty rack for over a year. I have a NMO mounted through the roof that I used for 2m. I have since replaced the 2m antenna with a GMRS antenna and use it instead of the Nagoya.  I now use the 72G on my wife's Honda with no roof rack and see no difference in TX or RX. Same radio, same antenna. I understand this is anecdotal and of course, YMMV.