As the R&O is public, users of the band have been commenting on it. It appears that they may not share the opinion that it is a "win for Amateur Radio." 73, Dick Norton, N6AA Some extracted comments follow: The EIRP limit was not part of the original proposal, and it’s of concern to operators on that band. The main arguments seem to be as follows: EIRP increases with antenna gain, and that gain keeps Amateur signals away from vehicles. Current Amateur state of the art EIRPs well above the proposed limit have caused no interference problems to date. Other services with higher limits near that frequency range are considered so unlikely to cause interference that they are very loosely regulated. Amateur signals are typically very narrow-band and should have no impact on wide-band radars even if they were detected, which is unlikely. The EIRP limit will kill Amateur innovation and progress on this b <band.n6aa@arrl.org>and. With a 1m dish this EIRP implies a 1mw transmit power limit. This is currently 20 db less than amateur state-of-the-art. It would seem to preclude any EME use of the band, estimates being that an EIRP of +100dbm is required For all practical purpose, this rolls the clock backwards to what was done a decade or so ago. Even a diode multiplier with a two foot dish (52 dBi) could exceed the limit. Today's 100 mW with a one foot dish (46 dBi, 66 dB EIRP) is way over. I agree that it would shut down 'normal' ham use ... can we argue that EIRP ignores the fact that we tend to use pencil beams (high gain, sharp dishes) and narrow bandwidths from remote (mountain top, not near a highway) locations? Our typical use should not pose any threat to wide band swept automotive radars. I run a 1m dish. Many others up here are using 1’ to 2’ dishes with 100mw or +72dbm EIRP. Sergei RW3BP and Al W5LUA are pursuing EME. A number of use are using converted E-Band Gigabeam (or similar) units. This FCC licensed fixed service operates in 71-76 and 81-86 GHz range, bracketing us. These units are more than 10 year old technology and have a bit more than +20 dBm transmit power and antenna gains a bit more than 51 dB, so an EIRP of about 70-75 dBm. I think the FCC rules are 55 dBW (maybe more) for that service. Because they use pencil beam antennas and because of the high path loss at these frequencies, they are very lightly regulated.... they all use the same single channel frequency and rely on antenna bearing and the high path loss to avoid interference... that's the FCC rationale for the light licensing (they simply pay a fee and check a database to make sure that their beam is not directly into another licensed unit a few km away. So, if we were limited to, say, +30 dBm, we would have headroom for some tech growth. BTW, I believe the auto radars are using similar transmit power levels. For up looking (EME and satellite) operations, a higher transmit power could be permitted as it is aimed away from the horizon and the road. The automotive folks used the reverse argument to avoid claims of interference with radio astronomy. The R&O's 'simplification' is to not have a rule about distance from the road, which I agree is hard to enforce. I think a better argument would be that equal EIRPs are not appropriate for services that use similar transmit powers but use widely differing antenna gain/beamwidth. With a narrow transmit beam, a moving vehicle will pass thru the beam quickly, if at all (the beam probably goes over the vehicle if from a mountaintop). The result is a very brief, very narrow band (few kHz or less) interference (if at all, with the high path loss), which should not affect the radar (which sweeps across GHz of spectrum) operation. Meanwhile, other vehicles nearby on the road are multiple interferers over wide spectrum at much shorter range. If the radars can (and must) tolerate each other over longer periods at closer range, they can tolerate a rare, extremely short and weak interruption. Further, for EME, higher EIRPs are needed, using both higher transmit power and higher gain, but they are looking up, so again the effect at road level is negligible. I believe the sharp beam means that in most cases the car is well out of our main beam, but even if they pass thru the beam, it's just a transient blip. The radar is sweeping across GHz of spectrum, and maybe hits out few kHz of signal on one or two sweeps. That CW signal does not fit the expected return signal from a radar target, which will have a varying frequency (same rate if the cars are same speed, slightly different rate if different speeds, but not a CW return). In the FFT spectrum that the FMCW radar is processing, one bin will flicker once, nothing like the return form a target, so should not trigger a false alarm. We will look like a one-time noise pulse at one freq. No reliable signal processing algorithm should respond to that. On Mon, Jun 26, 2017 at 11:34 AM, Christopher Imlay <w3kd.arrl@gmail.com> wrote:
Greetings. President Roderick has asked that I circulate to ODV the following, which I sent to the Executive Committee earlier today.
FCC has adopted a new procedure of circulating to the public draft Reports and Orders ahead of the time that they are considered at an upcoming FCC open meeting. In my view this is a great idea of Ajit Pai's and it is about time they threw a little sunshine on their actions.
FCC has released a DRAFT report and order, to be considered at its July 13 Open Meeting, to address the allocation status of the 76-81 GHz band. The 50-page draft report and order is attached, but the relevant portions are paragraphs 13-18 on pages 8 through 11.
Bottom line: Amateur Radio fared quite well here. On the upside, Amateurs retained an allocation in the entirety of 76-81 GHz; the FCC is removing the 19-year-old suspension of the use of 76-77 GHz by Amateurs (imposed in order to protect first generation vehicular radars ) so as to allow us access to that band once again; and this Order cements the Amateur allocation in the United States for many years to come.
On the downside, the small primary allocation that Amateurs had at 77-77.5 GHz has been reduced to secondary status to match the remainder of the 76-81 GHz segment , but the secondary status that we have had for many years in the remainder of the band has not been a limiting factor due to the high level of frequency re-use possible as the result of propagation limitations and other factors . Also, to have a consistent power level among the various services sharing this segment , FCC has imposed a power limit of 55 dBm EIRP (which translates in the proposed rules to 316 watts EIRP). The proposal that Robert Bosch, LLC made was that there was ample compatibility between vehicular radars and Amateur Radio and that no power limit was necessary for Amateur Radio , but several automotive manufacturers asked that Amateur Radio be ousted from the band. Delphi Automotive asked for a power limit . An n individual amateur indicated that some Amateur operations in the band were currently at between 66-71 dBm. I have not checked with the ARRL laboratory staff about the impact of a 316-watt EIRP limit on Amateur "hilltopping" but will do so shortly.
This was resolved reasonably favorably to Amateur Radio largely because of the coordinated support between Bosch and ARRL. I consider it a win for Amateur Radio overall.
73, Chris W3KD -- Christopher D. Imlay Booth, Freret & Imlay, LLC 14356 Cape May Road Silver Spring, Maryland 20904-6011 (301) 384-5525 telephone (301) 384-6384 facsimile W3KD@ARRL.ORG
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