RF Exposure Docuemnt

 

RF Exposure at Station K2ENF

Overview:

The purpose of this document is to satisfy the requirements of the FCC as regards RF exposure ¹ at the station and it’s documentation. All measurements and calculations are effective as of this document’s writing, 7/1/22, and are true to the best of my understanding.

K2ENF is an amateur radio station, which is located at 84 Wolcott Ave, Rochester, NY 14606. (43.17N / 77.70w) The address is a private home located in Located in the town of Gates, NY, which is physically to the west-northwest of Rochester’s downtown area.

Equipment at K2ENF:

K2ENF employs as it’s main transceiver , a Yaesu FT-991a,² which is capable of Am, FM, SSB, C4FM and CW. It has band coverage as follows:

Band	Modes	Max Power in PEP
160m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
80m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
60m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
40m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
30m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
20m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
17m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
12m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
10m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
6m	AM, FM,SSB,RTTY, and data modes	100watts PEP,TPO
2m	AM, FM,SSB,RTTY, and data modes	50w PEP,TPO
.7m	AM, FM,SSB,RTTY, and data modes	50w PEP,TPO

Other transmitters at K2ENF

K2ENF also employs three mobile units, and several portable units which are less powerful and therefore outside the scope of the RF exposure guidelines, and so are not a significant part of this examination. Mention is made for the sake of completeness, only.

Antennas at K2ENF:

The station normally employs three separate antennas for transmitting. ³

1. A VHF/UHF antenna (Tram) Being a fairly standard co linear design, it has 8dbi of gain at VHF frequencies, and 11,7dbi of gain at UHF frequencies. It is mounted on a 12ft metal pole which is in turn, ground mounted. This 12ft pole is fastened to the house by means of a custom mount, which reaches over the edge of the roof, to secure the mast. This places the antenna tip at 34~ ft Height above ground level. (HAG)

2. An IMAX-2000, which is designed and sold as a CB (11m) antenna, but is capable of being operated at 6m-17m. It is center turned at 10m. It is a fibreglass style vertical, in a colinear design. The advertised gain for this antenna at center tune is 5.2DBi. It is mounted on a 12ft metal pole which is in turn, ground mounted. This 12ft pole is fastened to the house by means of a custom mount, which reaches over the edge of the roof to secure the mast. This places the antenna tip at 38 ft Height above ground level. (HAG)

3. An 80m End-fed halfwave (EFHW) which covers all the HF bands the radio covers. It is normally used only for 80-20m, though occasionally is used for 10m and 6m…. the latter with the aid of an Antenna tuner. (ATU). At it’s highest point it is perhaps 45ft up. While the standard gain for such an antenna were it installed in a more or less straight line, is normally regarded as being 2 dBi, the unique installation which is required by the rather small space it’s installed in, compromises that normal figure greatly. *⁴

Important note: K2ENF has gone to some lengths to ensure that all antennas are located in an enclosed and gated back yard, and are essentially inaccessible to outsiders, absent a serious breech of trespassing laws. Thus the only exposure would be to those with legal access to the yard and who are therefore familiar with the station and it’s operation.

FCC requirements for evaluation of RF exposure ⁵

Band	Maximum TPO of FT-991a:	Evaluation required by the FCC if TPO exceeds:
160n	100w	500w
80m	100w	500w
75m	100w	500w
60m (assumed)6	100w	500w
40m	100w	500w
30m	100w	425w
20m	100w	225w
17m	100w	125w
15m	100w	100w
12m	100w	75w (evaluation required)
10m	100w	50w (evaluation required)
2m	50w	50w
.7m	50w	50w

Conclusion:

K2ENF is in compliance with the FCC’s RF exposure guidelines, without any modification to existing equipment, or of existing real estate fixtures. By the FCC’s definition, (By way of the listed document), there are only two operational bands where this evaluation is even required. Those being 10m and 12m. Given the antenna installations and the physically limited access, station K2ENF, at worst, poses a very limited RF exposure threat. Therefore, it should also be noted that this document goes well beyond the FCC’s stated requirements for reporting such exposure.

Even exclusive of matters like duty cycle for various modes…. And even assuming 100% duty cycle, the conclusion regarding the threat of RF exposure comes down to distance from the antennas used for these two bands the commission says should be evaluated. Since both the antennas employed in the required bands and power levels ( are well over 2m away from any living being, based on height above ground level alone), even if someone were to be standing directly below them, (Unlikely given they are both in a fenced in back yard) it is felt that in no case are emissions from K2ENF outside the boundaries of the FCC rules as regards RF exposure.

This document will be updated as required by equipment changes.

1(See the FCC's Rules and Regulations [47 C.F.R. 1.1307(b), 1.1310, 2.1091, 2.1093]. )

2See: https://www.yaesu.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=102&encProdID=490C4A71118AD0F4E825E89D821B73BB&DivisionID=65&isArchived=0&currTab=tab_Description&currDiv=DescriptionDiv&ExpandID=2077,Features

3 These are semi-permanent. Owing to the experimental nature of Amateur radio, other antennas may be employed on a temporary basis from time to time, but listed here are the ones that are a more permanent part of the station.

4 The antenna is a typical end fed, fed by a 49:1 transformer and lofted horizontally, (more or less) with a peak height of 45ft, at 132ft long, but due to the size of the property, it is almost a loop, running around the fence line of the back yard. It is fed at the 10foot level on the southwest corner of the back yard, and runs through several trees along the fence line around the edges of the property, and comes back up to nearly the feed point. Antenna modeling, not included here, has suggested that its configuration actually creates some loss of effective radiated power, instead of the usual 2.1 dBi gain. Also, because of the height above ground, (less than a half wavelength) it is further assumed most of the radiated power goes more or less straight up. (NVIS) It is thereby assumed to be less of an RF exposure hazard at ground level.

5(Source for FCC requirements: https://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/oet65b.pdf

6The figures for 60m are assumed, and added in a desire for completeness, because the specified FCC document makes no mention of the 60m band, and yet the station is capable of operating there.