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Author Topic: NOAA weather radio station KWO35 RFI issues with Coast Guard?  (Read 26005 times)
KE2KB
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Posts: 127




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« on: August 21, 2013, 07:17:37 AM »

Hi;
Living in NJ, the NOAA station I get the strongest signal on (and the only one my SAME receiver will receive with supplied whip) is KWO35 at Upton NY. For the past 6 weeks or so, that station has been mostly off the air. When I checked the other day on NOAA site, I learned that the problem is that their station is causing interference with the Coast Guard. That leaves me with a few questions.
Why was this not a problem until recently? By any chance did the Coast Guard purchase some new radios that are less selective (and therefore less expensive)?
Did the CG recently begin using a new band?
Is there really something wrong with the NOAA transmitter which causes it to emit spurious signals that are stronger or at a different frequency than in the past?

While this is being resolved, I have no SAME service, unless I connect my Ringo Ranger to the ext antenna jack on the receiver. That is really not an issue though, as it is usually obvious when severe weather is approaching, and I can use my VX-150 to receive one of several NOAA stations. I always receive the station on Hamburg Mountain in western NJ, and frequently the Allentown PA station. With the Upton station being off the air, I sometimes receive the Philly or Delaware station on 162.550. Scanning for what NOAA stations I can receive is also a good indicator as to whether or not the 2m band is open.

Anyone have more info on this?

Thanks

KE2KB
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K1CJS
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« Reply #1 on: August 22, 2013, 06:09:19 AM »

The KWO35 transmitter is atop the GE building at 30 Rockefeller Center in NYC.  It is not in Upton, rather it is controlled/programmed from there.  There have been long standing reports of problems with that transmitter, it is only the latest that claims interference with the Coast Guard.  When it will be back on the air permanently is a question that only time will tell since troubleshooting and remedying the problems have been ongoing.
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KE2KB
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Posts: 127




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« Reply #2 on: August 22, 2013, 05:10:57 PM »

Thanks for the info. I read the station info wrong, thinking Upton was the Xmitter location and NYC was the origin of the broadcast. That made me wonder why the station was so strong here in Eastern NJ.
As of 20:10 on 8/22 the station is up, but it has been on and off all day.

KE2KB
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AA4HA
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« Reply #3 on: August 23, 2013, 04:39:13 AM »

As of 20:10 on 8/22 the station is up, but it has been on and off all day.

It sounds like they are actively working on the problem. Usually it is not "that" hard to figure out what that type of problem is with a transmitter.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
K1CJS
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« Reply #4 on: August 25, 2013, 05:43:53 AM »

Yes, but sometimes one 'fix' will produce another problem, especially in areas that have numerous transmitters, and that may be the case here.  It was mentioned in the article I saw that they were actively working on the problems and hoped to have them solved in short order--if they could finally get rid of the intermod problems that seemed to be popping back up when they solved other problems plaguing that transmitter--and still keep it's area as wide as it was.
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KD0REQ
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« Reply #5 on: August 27, 2013, 12:19:49 PM »

there are probably only a couple of feedlines up to a zillion antennas, and they have to go through a forest of diplexers -- which is the case with the Shoreview Tower Farm here in the twin cities.  had an interesting ham club presentation on the "Fox tower" a few months back.  everything interleaves into one big hardline, basically, and you have to tune the system with any changes. (the other tower is co-operated by KSTP and WCCO.)

don't want that job.  as a young'un in TV, a favorite story of our transmitter engineer was the new transmitter for PBS in the building, and the day they burned through the diplexer on their hardline between audio and video stages because it was not exactly adjusted right for that unit.
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WA2CLP
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« Reply #6 on: September 07, 2013, 07:21:36 AM »

I've tried to get some more specifics from NOAA but they don't have much info. This problem sounds like a job for one of the local Ham Radio Clubs to solve. The NOAA broadcast from Sussex NJ area on 162.50 Mhz states there's a problem with Marine channel 60 however I don't see any listing for such a channel. Anyone have more info?
Dan WA2CLP
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N4NLQ
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« Reply #7 on: September 09, 2013, 02:19:40 PM »

Marine channel 60 is listed as a 4.6 mHz split channel in one chart I found.                       

Ship station   Coast station
  156.025         160.625

The same chart, supposedly current, however said it is not used in the U.S.  Another chart I found, dated Sept. 2013, listed it as a required operating capability for vessels over 300 tons.  Confusing?

But at any rate, yes  there is a Marine channel 60.

Allan
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KE2KB
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« Reply #8 on: November 16, 2013, 04:36:37 PM »

Had a thought;
Could it be the CG's radios, and not the NOAA transmitter?
Did the CG recently purchase new radios, or change to a new frequency?

KE2KB
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KF7CG
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« Reply #9 on: November 18, 2013, 10:50:45 AM »

Depending on the sensitivity and desense resistance of the Coast Guard receiver this one might not be so easy to kill off. The Coast Gurard transmit 3rd harmonic mixed with the second harmonic of the NOA station is close enough in frequency to possible cause receiver desense depending on how open the front and of the CG receiver is.

KF7CG
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K1CJS
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« Reply #10 on: November 19, 2013, 06:26:45 AM »

Depending on the sensitivity and desense resistance of the Coast Guard receiver this one might not be so easy to kill off. The Coast Gurard transmit 3rd harmonic mixed with the second harmonic of the NOA station is close enough in frequency to possible cause receiver desense depending on how open the front and of the CG receiver is.

That's part of what I meant in reply 4.  Various measures tried in mitigation of the problem could result in more problems.
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KE2KB
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« Reply #11 on: March 05, 2014, 08:42:11 AM »

Update:
I just read that the KWO35 radio transmitter is being relocated within the next 6 months. The article (in Wikipedia) says the current location of the transmitter is atop the Met Life building in Manhattan. I wonder how far the transmitter must be relocated in order to eliminate the interference problem.
I wonder whether anyone thought of changing the broadcast frequency of KWO35. There are several other frequencies that are not used by any nearby stations.For example, 162.525Mhz. From my location in Teaneck NJ, using my VX-150 with a Ringo Ranger ARX-2B on the roof I usually do not received a station on that frequency. Depending on band conditions, I can receive NOAA stations from as far away as south Jersey/Philly/Delaware, Harrisburg PA, and occasionally even Burlington VT (or is it Montpelier?). With KWO35 being our of service, I receive the Harrisburg station on that frequency.

KE2KB
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KF7CG
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« Reply #12 on: March 05, 2014, 11:10:04 AM »

If it is desensing from intermod, 25 KHz may not be a big enough frequency shift. On all bands and services, intermod has become a larger and larger problem as the bandwidth of receiver front-ends have increased.

The older narrow band single band front-ends were more intermod resistant.

KF7CG
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KD0PBO
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Posts: 67




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« Reply #13 on: March 07, 2014, 10:20:53 PM »

Maybe they received reports or heard first hand, interference on some of the "emergency call" frequencies within the marine traffic band. Its not far from the VHF section for NOAA so it could be a possibility.

Near coastal cities with a lot of commercial marine traffic and being a constant 24/7 possible source of interference, I could see why that would pose a greater problem to both the GC and the safety of boat traffic.

Just a thought though..


Semper Paratus & 73
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W8JI
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« Reply #14 on: March 08, 2014, 10:24:35 AM »

M
  156.025         160.625

The same chart, supposedly current, however said it is not used in the U.S.  Another chart I found, dated Sept. 2013, listed it as a required operating capability for vessels over 300 tons.  Confusing?


160.625 minus 156.025 is 4.6. This means all possible intermod products start at 4.6 below the lowest and above the highest and extend outwards. You have to ignore the two base frequencies. This is NOT a likely cause, because the TX on 156.025 would be dark when the RX was on. So everyone is looking at the wrong thing.


There has to be other transmitters or spurious signals involved, it cannot be harmonics or mixing of harmonics of the two base frequencies.
 
While this is the wrong thing to look at, IM products would be 4.6 and multiple of 4.6 minus or plus either carrier and you have to ignore the carriers:

starting at -7th order
142.225
146.825
151.425
156.025 1st carrier ignore in IM
160.625 2nd carrier ignore in IM
165.225
169.825
174.425
finished at +7th order

Again, it is technically impossible for two simplex systems to IM each other.  It has to either be spurious or other transmitters involved.


fund ignore impossible
165.225
169.825
174.425
142.225
146.825
152.425
156.025
 

 
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