HHS-OASH-2026-0397-4393
https://www.regulations.gov/comment/HHS-OASH-2026-0397-4393

Re: HHS-OASH-2026-0397 - Supplemental explanation of occupational RF site exhibit
Prior comment tracking number: mv5-i6d1-04w6

Please consider this supplemental comment with my prior submission identified above. It explains the accompanying "HHS RF site illustration" exhibit, which depicts the University of Illinois/Willard Airport (CMI) radar and communications site in the Champaign-Urbana area of Illinois. I recall the 17-ft platform configuration as approximately 1990-2000; the exact tower-elevation date is unknown. The drawing shows ATCBI-5 after its replacement of ATCBI-3 during that period. It explains the site and simultaneous-source assessment questions.

HOW TO USE THE EXHIBIT

The accompanying PDF contains Figure 1, equipment and power tables, source context and limitations. Read the numbered work areas together with the figure: radar platform (1), northeast and southeast radio platforms (2 and 3), and equipment shelter (4). Orange identifies the ASR radar and cyan the directional beacon; radio envelopes surround the ground-radio platforms.

Figure 1 shows the source patterns together in a schematic simultaneous-source view. It does not establish that every radio channel transmitted at once during a historical task, or that the antenna was stationary and energized.

HOW IT WAS CREATED AND WHAT IT USES

The exhibit was prepared with three-dimensional computer graphics using my equipment and work-location recollections, stated equipment parameters, schematic site geometry and published technical information. It is not an FAA-produced model, a surveyed site plan or a measurement-based electromagnetic simulation.

I recall that ATCBI-3 was replaced by ATCBI-5 while the tower remained in its 17-ft configuration; I do not remember the replacement date. I also recall frequent simulcasting, GRT transmitter output of 10 W per transmitter, and transmission-line loss as high as 2 dB. Exact channel-specific losses and historical simulcast combinations remain unresolved.

Power labels distinguish peak and pulse-averaged transmitter output from power reaching a worker. GRT output is 10 W (40 dBm); 2 dB line loss leaves 38 dBm (6.31 W) at the antenna.

Radio envelopes are schematic. Channel-specific line losses are unknown; no frequency-dependent loss curve is assigned. The still image does not reconstruct controller-pilot exchanges or historical keying; aircraft emissions are not depicted. The five-channel simulcast grouping is an example. Broad coverage surfaces, fading layers and reflection overlays are illustrative. Dimensions and antenna-center heights remain schematic. NTIA Report 13-490, Table C-1, provides generic ASR-8 context; the illustration uses a 1.35 degrees horizontal beamwidth, while NTIA lists 2.3 degrees for a generic ASR-8. The site-specific beamwidth remains unverified.

WHAT IT DEMONSTRATES

VHF, UHF and microwave radiation is invisible. I challenge HHS reviewers to imagine themselves at the numbered work areas in Figure 1, with their own bodies among the operating sources. The body encounters the combined environment. Near fields can be strong and uneven; their strength requires task-specific assessment. Ask what reaches the body during repeated maintenance, what shielding provides, and what measurements and health monitoring are needed. The colors make the unseen environment imaginable; they do not quantify bodily exposure.

WHAT IT CANNOT DEMONSTRATE

The exhibit does not determine my personal RF exposure, establish a limit exceedance, prove disease causation or certify a safe location. Envelope size, color, brightness and overlap are not calibrated field strength, absorbed energy or dose. The 300-ft radar drawing cutoff is not a near-field boundary or the stated 60-nautical-mile service range. The shelter remains a spatial reference, not a realistic view from 60 miles away. Reflection overlays do not solve the indoor field or quantify reflected power. Close-range fields, cabinet leakage, shielding changes, interference and building transmission require separate assessment. Possible equipment-generated X-rays are a distinct ionizing-radiation question and are not modeled here.

I ask HHS to use this exhibit as an explanatory aid supporting task-specific assessment, accessible exposure records and meaningful communication of findings to workers and physicians. FAA assessments and occupational-health decisions should account for actual energized maintenance conditions and simultaneous sources. Current and retired technicians should be included in the research and follow-up needed to resolve those questions.