[BC] RFI near Empire State Building

[R A Meuser]

Bob

I would not dispute your technical comments, but what I posted was an 
estimate that if you look at the numbers has over a 100% fudge 
factor. Of course it would be difficult to make an accurate wideband 
voltage measurement which would probably be meaningless as it relates 
to what an vehicular RFID would see anyway. Free space loss has any 
one UHF source is a low of about 400 millivolts to a high of over 2 
volts, depending on the station and the direction. A number of 
locations where cars are having problems such as around Madison 
Square garden are a good free space path. The article seems to 
reference a number of incidents on 35th street between Lexington and 
Madison, pretty clear shots. We do not know the actual data, only 
what the Daily News printed, but I would bet there are no problems on 
33rd or 34th between 5th and 6th or 5th and 6th between 33rd and 34th streets.

Regarding antennas, as I am sure you recall, the CBS DTV antenna was 
described at the time as a science project intended to get HDTV on 
air for the 1998 winter Olympics. We all know that did not 
happen.   The antenna was placed in the existing CBS aperture on the 
tower. At the time there was a fully circular UHF antenna on top of 
the tower. No other station had any interest in that antenna until 
after 911 and even then it took quite some time to get everything 
organized. There was an equally poorly situated master DTV antenna on WTC.

A number of us got a good laugh when we saw the drawing for the MOAPA 
and were wondering what whomever thought it would actually be built 
was smoking.

After Feb 2009, the DTV master will be shut down so that major 
revisions to the pattern can be made.



Bob Tarsio wrote:
>Robert:
>It is difficult to predict with calculated data what the actual field
>intensity at street level will be. We are talking about one of the most
>diverse reflective and absorptive environments known to RF transmission.
>With high fields from reflections it is quite possible that the field
>intensities are much less than predicted for smooth earth at street level.
>This is a real problem in and around Manhattan particularly for that CBS DTV
>antenna due its poor circularity. Side mounting on that tower was a poor
>alternative to top mounting which was not possible at the time CBS did that
>project. The tower was reinforced a couple of years ago to support the
>present configuration but with the 1950 era Stainless tower it was not
>possible to support the original proposal for a top mounted panel antenna
>affectionately known at the time as MOAPA or mother of all panel antennas.
>Just so you don't think I am making off hand comments about Empire I wrote
>the specifications for all three of the FM antennas and combiner systems
>presently in use at Empire. I was project manager for the VHF combiner and
>the larger of the two ERI FM combiners systems projects in use there too. I
>have made extensive RF safety measurements in and around the building being
>retained by Helmsley Spear, CBS, ABC, Skyline Tower Service, ERI, and Con
>Edison. I also worked as a field engineer for Silliman & Silliman during the
>early RFR measurements that were made in the building as far back as 1987. I
>am routinely retained as the RF safety engineer of record for any
>maintenance performed on the outside of the building requiring station
>shutdowns. I can tell you this from my experience up there, predicted field
>intensities invariably differ from measured results usually on the low side
>but not always. Re radiation absorption and antenna performance all play a
>role in this phenomenon. Every antenna project since the mid 1980s has
>always worked toward the goal of reducing downward radiation when possible.
>The exception was the new mini master FM antenna which is a single bay
>antenna. But even this antenna did reduce somewhat the total downward
>contribution in that it replaced three separate single bay antennas. Two of
>those antennas one an RCA and the other an MCI panel were located lower on
>the tower. The elimination of those antennas offered slightly less FM RF in
>the downward direction by virtue of the fact that all three FM stations
>previously using separate antennas are now utilizing the same single bay
>antenna at a greater distance from where people are in and around the
>observatories.
>I am not saying that there aren't higher than usually expected field
>strengths around Empire. I only take issue for using predicted data for
>anything other than an academic exercise.
>Bob Tarsio