NOAA NYC Shutdown Interference USCG 16

[rr60]

Public information statement
national weather service new york ny
345 pm edt fri oct 4 2013

noaa weather radio new york city remains out of service...

The noaa weather radio transmitter that serves the new york city
metropolitan area has been causing radio frequency interference on
the u.s. Coast guard channel 16 transmitter for international
distress...safety and calling since late july.

The new york city transmitter broadcasts on a frequency of 162.550
mhz and the u.s.coast guard transmitter broadcasts on a frequency of
156.800 mhz. Other transmitters...in very close proximity to the nyc
transmitter broadcast on a frequency of 168.3 mhz.

The national weather service is working with several u.s. Government
agencies to isolate and resolve this technical problem. We have
installed a filter on the nyc transmitter...which reduced...but did
not eliminate this problem. We worked with another federal agency
and oversaw the installation of another filter...on a transmitter
broadcasting over 168.3 mhz...which did not further reduce the radio
frequency interference.

We continue to work with the u.s. Coast guard to resolve this
problem and apologize for the interruption of our routine weather
broadcasts.


...noaa weather radio will be placed in operation to broadcast
short fuse life threatening weather watches and warnings...

Note that the nyc transmitter will be placed in operation for the
issuance of short fuse life threatening weather watches and
warnings...such as tornado...severe thunderstorm and flash flood
watches and warnings...to ensure dissemination through the emergency
alert system...which is carried by the broadcast media.

Thanks for your patience and for listening to noaa weather radio.

We will periodically provide you with updates on the status of the
new york city noaa weather radio transmitter via these public
information statements.

 

[902]

This has been an ongoing situation that some local folks in NE NJ and NYC have been deeply concerned about. Apparently there is a mixing product ("Intermod") where 162.55 factors into the equation.

This should go without saying, but hopefully there is a ferrite circulator and harmonic filter installed on each transmitter. Being a realist, we don't always see those obvious solutions implemented.

The mix could be happening anywhere, considering how much of an RF-dense environment Manhattan is.

Wonder why it wasn't moved to Alpine, Fort Lee, Creedmooe, Court Plaza, Nassau, or wherever (the whole lot of us could probably name three dozen more "just as good" sites), instead of being completely shut down, but the answer to that may be like the old Tootsie Pop owl commercial: the world may never know.

The system didn't seem to have battery backups when it was working, either.

 

[rapidcharger]

Interesting. Is there not another open frequency the weather broadcast can move to?

 

[902]

Interesting. Is there not another open frequency the weather broadcast can move to?

KWO35 has been on the air on 162.55 since I was a kid (and very likely pre-dates me, but my friend and familiar voice from when the meteorologists were at the mic is now SK, so I don't have anyone to ask about history anymore).

What I find difficult to believe is that an agency spectrum manager could not work with IRAC to come up with another non-offended frequency, or that the site could not be moved (my NYC friends tell me it's into a combiner on the Conde' Nast building now and no longer on the "RCA building" [yeah, I know...] and it STILL has no backup power...). The general rule of radio is last in has to accommodate all of the existing systems, so in anywhere but bizzaro world, the well-established NWS frequency would be a fixture to work around (in other words, everybody knows it's there, so why would it need to change, and why was it not accounted for in a comprehensive intermod analysis?).

From an armchair vantage point, it looks a lot like the higher-ups have fallen into a "nothing we can do" mentality by letting it go this long. In the mean time, there is transmitter in Hardystown (162.5) that "kinda" covers the hole, if you wrap some aluminum foil around the antenna. That's an embarrassment.

 

[rr60]

WHOIS 168.30?? I find nothing and hear nothing.

 

[rfburns]

Looks like 2x 162.55=325.1 minus 1y 168.3 equals 156.8. If that's the case, one would think it wouldn't be that difficult to eliminate with some ferrite and band reject filters. If it does go into a combiner maybe the combiner needs to be redesigned. If they've been working on it since July, you would think they know where the mix is occurring. Always difficult to figure out interference when you don't have all the facts. Hopefully someone here will ferret out some more info than what's in the public information statement.

 

[jaymatt1978]

An obvious question (yes someone has to ask) why cant NOAA NYC transmitter just change frequencies\?

 

[sfd119]

Probably because that would require a mass reprogramming of Weather radios. Most are setup on CHx with the FIPS code.

 

[902]

An obvious question (yes someone has to ask) why cant NOAA NYC transmitter just change frequencies\?

What SFD119 said, and not only that, the different frequency would affect the overlaps in coverage for whichever frequency was selected.

I have to toss out a "back in the day" here, but back in the day, the early 70s, the region only had three NOAA transmitters covering NJ. There was KWO35 in NYC on 162.55, KHB38 on 162.400 MHz in Atlantic City, and KIH28 in Philadelphia on 162.475 MHz. That's it. As hazardous weather awareness was adopted by the emergency management community and the NWS added other features through SAME, four more frequencies were allocated. These were for fill-ins that were placed in peripheral coverage areas that were unreliably covered by those original stations, sometimes by rural electrical co-ops, or local governments. There are similar geometric issues everywhere else in the country. Moving one affects the others and might cut their range due to contention.

 

[wtp]

more math

168.3-162.55=5.75

162.55-5.75=156.8

 

[dlwtrunked]

This has been an ongoing situation that some local folks in NE NJ and NYC have been deeply concerned about. Apparently there is a mixing product ("Intermod") where 162.55 factors into the equation.
QUOTE]

The equation is 2*162.55-168.3=156.8.

If the mix is being done external to either 162.55 or 168.3, which can happen, nothing can be done at either the 162.55 or 168.3 equipment.

 

[ChrisP]

WHOIS 168.30?? I find nothing and hear nothing.

It is the FBI, their channel H3.

- Chris

 

[jak122]

NOAA Channel Seven (162.550)

I have been experiencing the same problem here in Juneau, Alaska with the local NOAA weather station bursting through my three RS Pro-197s and two Realistic Pro-2006s on a regular and repeated basis.
These receivers are fed from discone antennas and have no pre-amps.

The problem has seemingly subsided a bit, however it persists randomly from time to time. I have adjusted squelch and attenuation controls to minimize this to the extreme, but it still happens.

Interestingly enough, the fine front ends of the Motorola two-way radios I use at work had the same problem.
It has died off somewhat, but still rears its ugly head now and then.

hmmmmm

 

[techman210]

It depends on physically, where the mix is occurring. If it is completely external, then there may not be much that can be done, other than good engineering (already has been mentioned, any may not be done) or dropping the TX power of one or more of the transmitters by 3dB or more and see if the problem disappears, or drastically diminishes.

if it is overload mixing in the 156.8 radio, then detuning the radio and inserting a GOOD high intercept point preamp may help. Since the mix is on-channel, traditional methods like cavity or crystal filters are not effective.

Unfortunately, in my experience, we see fewer and fewer qualified government techs in the field. Most new recruits from the military, and even private industry are box/module replacement experts and when handed an iso-tee and a spectrum analyzer with a tracking generator they become perplexed, and have no training or experience in solving mixing problems.

I have seen techs absolutely befuddled when a hilltop radio tests at 0.2uv sensitivity with a sig gen, and they wonder why the sensitivity goes to pot when they hook-up the antenna. They will say things like "the antenna is good, it tested at 1.2:1" while neglecting things like proper RX filtering, noise floor and the lack of additional circulators and tx/rx filtering beyond what their notch duplexer provides.

 

[902]

Unfortunately, in my experience, we see fewer and fewer qualified government techs in the field. Most new recruits from the military, and even private industry are box/module replacement experts and when handed an iso-tee and a spectrum analyzer with a tracking generator they become perplexed, and have no training or experience in solving mixing problems.

There are two kinds of radiomen. Gray and dead. This particular trend started about 20 years ago when one LMR manufacturer effectively eliminated component-level troubleshooting support, turning technicians into RRR guys (reset, reseat, replace... i.e., "boardswappers"). Got a base station? Better get the FRU (field replacement units... extra boards) kit for it. Eventually, it became a self-fulfilling prophecy because replacing a board and watching the red LED go green, or the computer diagnostic say "PASS" is cheaper than component-level technician labor, time and materials costs. And one doesn't need SMT rework technology.

It's gotten worse with an IT mentality, as complex communications systems are handed to CIOs to manage. A recent interview I had after 3 decades in professional radio asked me about computer networks. Yes, these systems use networks for transport and control now. But, really. Nothing about antennas, ERP calculations, intermod, site management, end-to-end tests, system optimization, nothing. And, after a while, it does not appear they want the gray, almost dead guy with decades of experience, anyway.

The NOAA thing is probably a help desk ticket somewhere in Washington that's waiting to be escalated.

 

[N1SQB]

I have been experiencing the same problem here in Juneau, Alaska with the local NOAA weather station bursting through my three RS Pro-197s and two Realistic Pro-2006s on a regular and repeated basis.
These receivers are fed from discone antennas and have no pre-amps.

The problem has seemingly subsided a bit, however it persists randomly from time to time. I have adjusted squelch and attenuation controls to minimize this to the extreme, but it still happens.

Interestingly enough, the fine front ends of the Motorola two-way radios I use at work had the same problem.
It has died off somewhat, but still rears its ugly head now and then.

hmmmmm

Jak, have you considered getting a notch filter for that frequency?
Check these guys out! I've dealt with them before. They can even tune a filter for the offending frequency.
http://www.parelectronics.com/scanner.php

Manny

 

[902]

If the mix is happening somewhere near by, but not under his control, the filter won't help. It would only help if the mix is happening in his front-end. If his work radios were getting it, too, there's probably rectification at a non-linear junction (rusty tower hardware? aluminum oxide? incompatible dissimilar metals?) somewhere.