[FOLLOW UP] iPhone 18 Pro Max Antenna Gain: Not an Apples to Apples Comparison

About two weeks ago, I published a blog piece on the iPhone 18 Pro Max antenna configuration disparities between the Apple C2 modem equipped international model and the Qualcomm X80 modem equipped US model, which is now a notable outlier in the latest Apple iPhone lineup.  I had not researched nor written any cellphone regulatory filing analysis in several years, but once the news was confirmed about the iPhone 18 Pro Max variant split between Apple and Qualcomm modems, I had a feeling that there could be some interesting RF differences lurking inside beyond just the two distinct cellular basebands.

Yes, once I started digging into the two separate FCC OET (Office of Engineering and Technology) filings for the international and US models, the antenna design dissimilarities became apparent almost immediately -- most notably the band n41 antenna configuration graph that I generated and used as an example in the previous article and have reproduced for reference below:

In the text of that earlier article, I alluded to similar discrepancies in other bands, such as low band n71, so a numerical and graphical follow up in that regard seems only natural.  And as we will see in the conclusion, those two bands were not selectively examined by coincidence.

In that low band n71 realm, the Qualcomm X80 model actually possesses a 0.10 dB (2 percent) greater peak antenna gain, though as the percent conversion shows, this difference is negligible.  What truly is notable, however, is the antenna gain consistency (or lack thereof) across the two iPhone 18 Pro Max models.  Each model incorporates two low band antennas, and focusing specifically on their lesser antennas, respectively, the Apple C2 model has a 1.80 dB (51 percent) antenna gain advantage.  That is significant, and it also is reflected in the average antenna gain figures, favoring the Apple C2 variant by 0.85 dB (22 percent) -- exactly the same average gain disparity displayed in the band n41 analysis.  See my n71 antenna graph:

This raises an interesting possibility.  Hearkening back to the 2010s period of a 3GPP GSM/W-CDMA and 3GPP2 CDMA2000 technology schism when Apple produced multiple distinct iPhone models for AT&T and T-Mobile versus those for Verizon and Sprint, could Apple at some point in its iPhone 18 Pro Max design and manufacturing phase have intended to supply T-Mobile with the Apple C2 modem equipped variant?  After all, mid band n41 and low band n71 are deployed extensively and almost exclusively in the US by T-Mobile.

Honestly, I doubt the theory holds much credibility -- just some circumstantial evidence, correlation not necessarily leading to causation.  Nonetheless, it is an interesting thought exercise, since the iPhone 18 Pro Max with Apple C2 modem that ended up as solely an international model appears in some ways to have had its antenna configuration optimized for T-Mobile in the US.

Source: FCC OET

iPhone 18 Pro Max Antenna Gain: Not an Apples to Apples Comparison

Yeah, I know that it has been a few years since I posted my last FCC OET (Office of Engineering and Technology) regulatory filing analysis, but when the news came down recently that the US variant iPhone 18 Pro Max (model A3473, FCC ID BCG-E9187A) would continue to utilize the Qualcomm X80 modem while the international variant (model A3716, FCC ID BCG-E9195A) would incorporate the new Apple C2 modem, my Spidey sense told me that a comparison between their two FCC OET filings might divulge some interesting data.  And, indeed, that proved to be true.

The executive summary is that the Qualcomm X80 based US variant and Apple C2 based international variant are not at parity with one another in their antenna configurations.  Generally speaking, the Apple modem international model is at an advantage, the Qualcomm modem US model at a disadvantage.

To illustrate, I examined the band n41 antenna configuration data from the two separate FCC OET filings and created the following graph:

Analyzing these mid band antenna gain numbers, the Apple modem is given a maximum antenna gain that is 1.30 dB (35 percent) greater than that of the Qualcomm modem.  Every band n41 antenna in the Apple modem equipped international variant has higher gain than that of the corresponding antenna in the Qualcomm modem equipped US variant, leading to an average antenna gain advantage of 0.85 dB (22 percent).  Spot checking other 5G NR bands, such as mid band n7 and low band n71, showed similar results favoring the antenna gains provided to the Apple C2 modem.

Before anyone jumps to conclusions that one modem is superior to the other, the differences in antenna gains have nothing directly to do with the Qualcomm and/or Apple modems.  Rather, the gain differences reflect two separate antenna hardware designs.  

Furthermore, do not assume that Apple is or is not stacking the deck in favor of its own modem silicon.  Some or all of the antenna design and performance disparity could come down to improved physical hardware layout from the Apple C2 modem integration and 5G NR mmWave absence in the international model.  The unfortunate takeaway, however, is that this creates an impediment to a true apples to apples modem comparison -- or Apple to Qualcomm modem comparison in this instance.  Any statistical or empirical differences in wireless performance (transmission and reception) out in the real world could boil down to the modems, the antennas, or both.

Oh, and for reference, I also checked antenna gains across multiple bands in the smaller iPhone 18 Pro US (model A3472, FCC ID BCG-E9186A) and international (model A3713, FCC ID BCG-E9192A) variants, both of which use the Apple C2 modem.  The important point of comparison is that their respective antenna gains are the same.  Only the iPhone 18 Pro Max is the outlier in this regard.

Source: FCC OET