With all the variations I've seen in Lat/Lon over the years, I've always figured if the Lat/Lon gets inside the perimeter fence, it's good enough for government work.
bp
<part15sbs{at}gmail{dot}com>
I always figured that using Google Earth for lat/lon and ground elevation is as accurate as I'm going to realistically get with any method that's available to me (yeah, I suppose I could pay a surveyor to go out there and get me better numbers, but that's not really going to happen). As long as I check a few points around the area and don't find any drastic (unexpected) differences in elevation, I figure it's pretty accurate.
Making a mistake in mounting height on the tower seems like a bigger concern to me... on smaller towers, I should be able to get within a few inches by counting tower sections, or even dropping a tape measure, but if you're up a few hundred feet, that can get a lot trickier.
On Mon, Dec 28, 2020 at 12:07 PM Ken Hohhof <[email protected]> wrote:
--IANAL but if I wanted to do an audit, I’d just check against Google Earth for lat/lon and ground elevation. That’s close enough nobody will care about the difference.
For azimuth, if you have the lat/lon of each end, you can calculate azimuth, assuming the antennas were aligned properly. If the RSSI is within a few dB of target, they were aligned properly. You can find azimuth by drawing a line on Google Earth, or using something like LinkPlanner.
I’d mostly be worried about xmt freq, channel width, and xmt power matching the license. It would be easy to miss the fact that frequency coordination showed you needed to dial back the xmt power, or to make a mistake and be on the wrong frequency. Those would be bad errors.
Tougher one to audit would be AGL. You coordinate the link, apply for your license, then tell the tower guys to mount the dish at 100 feet. But how do they determine 100 feet? Count tower sections? Foot markers on cable? Tape drop? Laser rangefinder? Maybe there’s a beacon light at the 100 feet so they put it at 90 or 110. Or there’s a nice abandoned mount at 120 feet so they put it there.
From: AF <[email protected]> On Behalf Of Steve Jones
Sent: Monday, December 28, 2020 11:44 AM
To: AnimalFarm Microwave Users Group <[email protected]>
Subject: Re: [AFMUG] FCC coordinate verification
hypothetical, If FCC was coming I would be freaking out. I just spend a lot of time nervous about all our licensed links and one day finding out we are just outside the margin, particularly on amsl. We use the smart aligner now to verify the coordinate, but I assume FCC has more accurate meter than me. Or I'm completely off and FCC equates to whoever FCC contract to come.
I can look at tolerance charts all day, but If I dont know what the tolerance is measured against, what value is it. Like if I want to get super accurate on weights I can go steal one of the ones in the jars and compare it to my weights
On Mon, Dec 28, 2020 at 11:02 AM Ken Hohhof <[email protected]> wrote:
When I had our frequency coordinator do an FAA application for us (licensed link on tower near airport) and mentioned the discussion here about 2C surveys, they acted like I was crazy. Are you sure this is required?
Steve, is this hypothetical, or is the FCC paying you a visit?
I know one time I discovered the commercial tower we were on had the lat/lon wrong on the ASR. For us to fix out license, they had to also fix the ASR. It was just a matter of filing a modification. I also seem to remember something about it wasn’t significant unless it was off by at least 1 second or something.
Honestly I just use the numbers from my Garmin 64st, same as for CPI data for CBRS. Given several minutes it will usually state accuracy within <10 feet. I check it against Google Earth and they usually match to better than that. Even the elevation AMSL usually matches. If there was a need for a survey I would think it would have to be for AMSL, there’s just no rational reason to need a surveyor to certify the lat/lon these days.
From: AF <[email protected]> On Behalf Of Steve Jones
Sent: Monday, December 28, 2020 10:41 AM
To: AnimalFarm Microwave Users Group <[email protected]>
Subject: Re: [AFMUG] FCC coordinate verification
im asking about if you get nailed by the FCC, not application
On Mon, Dec 28, 2020 at 10:13 AM Cameron Crum <[email protected]> wrote:
Typically if you are filing for FAA or FCC you have to supply coordinates from a 2C survey mimium. They assume a certified survey is good enough.
On Mon, Dec 28, 2020 at 10:02 AM Steve Jones <[email protected]> wrote:
Have any of you guys ever had the FCC verify your transmitter data?
What equipment do they use to verify elevation and coordinate?
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