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Author Topic:   Receiver Testing with NOAA Weather Radio Broadcasts
jimh posted 03-27-2013 10:53 AM ET (US)   Profile for jimh   Send Email to jimh  
I have written about testing VHF Marine Band radio receivers by using weather radio broadcasts. I thought I would use my own method to test a radio I had on the bench, and also test my antenna installation. Here are some observations:

On WX-1, 162.550-MHz, I got a tremendous signal from KEC63, the NOAA station that is literally just down the street from me. The distance is about three miles. This is not a good signal to use for testing receiver sensitivity, but it does have value. It is such a strong signal that it helps to test receiver rejection of strong adjacent channel signals. Some receivers might be completely overloaded by the signal level from a local transmitter like KEC63. That other stations can be received in the presence of this very strong signal is a good indication the receiver has good overload and intermodulation performance.

On WX-2, 162.400-MHz, I got a decent signal from KHB97 in Sandusky, Ohio, about 80-miles away from me. Their coverage is shown by

http://www.nws.noaa.gov/nwr/Maps/PHP/site.php?State=OH&Site=KHB97

and some reception in my area is indicated as possible (by the green segment in SW Oakland County). This signal was heard with some heterodyne artifacts, which are probably from a competing signal from Sarnia, VJV492. This Canadian station is lower power (42-watts) and is not in the main lobe of my directional antenna as shown in

http://www.michiguide.com/weather/nwr/xjv492.html

but I can hear it beating with KHB97.

On WX-3, 162.475-MHz, I got a very strong signal from VAZ533 in Windsor, Ontario, a path of about 27-miles. Their coverage is shown in

http://www.michiguide.com/weather/nwr/vaz533.html

and they are right in the main lobe of my antenna.

On WX-9, 161.775, I heard the continuous marine broadcast from Environment Canada. This is actually on VHF Marine Band Channel 83B. The service is transmitted simultaneously by several stations. I believe I was listening to the transmitter in Leamington, Ontario, call sign VBE-2. These stations do not individually identify themselves. VBE-2 is a path of 42-miles. I could not find any coverage map for VBE-2.

To summarize:

WX-1: 3-miles
WX-2: 80-miles
WX-3: 27-miles
WX-9: 42-miles

These results seem consistent with an antenna and radio that are operating normally.

jimh posted 03-27-2013 11:02 AM ET (US)     Profile for jimh  Send Email to jimh     
I also observed that the radio receiver was able to receive my local NOAA weather radio signal without the antenna being directly connected. While the radio could not receive the local station with no antenna connected, as the transmission line for the antenna was brought near the radio's antenna connector, the receiver began to receive the local station as the two connectors were brought in close proximity. This is a good indication of how a receiver might be able to receive strong signals when there was actually no direct connection to the antenna due to some discontinuity in the transmission line or the connectors. The local NOAA weather station could be copied with the antenna transmission line connector just held close to the radio antenna connector, without any direct contact. It is this sort of good sensitivity in a radio that often fools people into thinking the radio is able to receive but not transmit. A modern VHF Marine Band radio has such excellent sensitivity it can receive very weak signals, like those provided by antennas that are not quite connected.
jimh posted 03-27-2013 11:08 AM ET (US)     Profile for jimh  Send Email to jimh     
My test results above also show the antenna was exhibiting the expected directional pattern. The only stations received were all in the main lobe of the antenna pattern, which is oriented to the SE (in order to maximize reception of ships in the Detroit River for the AIS receiver that is usually connected to this directional antenna). I would normally expect to receive other NOAA weather radio stations from other directions, but the excellent pattern of the antenna has suppressed their signals.
jimh posted 03-31-2013 10:30 AM ET (US)     Profile for jimh  Send Email to jimh     
Checking the weather signals today, I am also copying WNG647 broadcasting on WX-5 or 162.450-MHz. The transmitter is located in Adrian, Michigan. The coverage map and other information is shown at

http://www.michiguide.com/weather/nwr/wng647.html

and indicates the path is about 59-miles. The signal is not in the main lobe of my directional antenna, and the received signal was noisy and on the edge of squelching out. However, it was decent copy.

jimh posted 04-01-2013 09:34 AM ET (US)     Profile for jimh  Send Email to jimh     
For use with GOOGLE EARTH there is a keyhole mark-up language (KML) file of data about NOAA weather broadcast transmitter locations that can be helpful in finding the various NOAA stations. You can obtain the file from

https://maps.google.com/maps/ms?ie=UTF8&oe=UTF8&msa=0& msid=204022826143008654763.000489582352df53aad1e

Use the hyper-link marked "KML" to save the file on your local computer. From the saved file you can import the data to your saved places for Google Earth.

I found that in some cases the location of the transmitter is not quite exactly shown, but it is generally close enough to be useful in estimating the distance to the station from you receiver for the purpose of assessing the path length.

jimh posted 04-09-2013 01:34 PM ET (US)     Profile for jimh  Send Email to jimh     
Checking the weather signals today, I found I was receiving WNG698 on 162.500-MHz on WX-6, located Grafton, Ohio. The coverage map of this station falls far short of my location:

http://www.nws.noaa.gov/nwr/Maps/PHP/site.php?State=OH&Site=WNG698

but the signal was good copy, although subject to some fading. The path is 105-miles.

Here are two recordings of the signals received. First, a decent signal from KHB97 on the path of 80-miles:

http://continuouswave.com/whaler/movies/KHB97.mp4

At the end of the above recording you can hear the hetrodyne of the other station underneath the main signal.

Next, a noisy signal with some fading from WNG698 on the path of 105-miles:

http://continuouswave.com/whaler/movies/WNG698.mp4

Also this afternoon, I heard KXI-94 from Angola, Indianna on WX-4 or 162.425. This was very spotty copy with some deep fading. The path is 104 miles and is off the side of the main lobe of the antenna. Their coverage map shows little signal coming this way.

The DX Comprehensive Summary

WX-1, 162.550-MHz: 3-miles, KEC63, Southfield Michigan
WX-2, 162.400-MHz: 80-miles, KHB97, Belleview, Ohio
WX-3, 162.475-MHz: 27-miles, VAZ533, Windsor, Ontario
WX-4, 162.425-Mhz: 104-miles, KXI94, Angola, Indiana
WX-5, 162.450-MHz: 59-miles, WNG647, Adrian, Michigan
WX-6, 162.500-MHz: 105-miles, WNG698, Grafton, Ohio
WX-9, 161.775-MHz: 42-miles, VBE2, Leamington, Ontario

jimh posted 04-30-2013 11:02 AM ET (US)     Profile for jimh  Send Email to jimh     
While tuning the weather band this morning, I caught the station identification of KZZ47 from Carey, Ohio, on WX-7 or 162.525-Mhz. Their coverage map

http://www.nws.noaa.gov/nwr/Maps/PHP/site.php?State=OH&Site=KZZ47

shows no signal anticipated at all in my location. Their signal was very weak, and only readable is short increments when the signal rose out of the noise for a few seconds. The path to KZZ47 from my location is about 110-miles, and most of it over land. Perhaps more noteworthy is the receiver was able to detect and demodulate this extremely weak signal while listening only 25-kHz away from the local KEC63 signal, which is extraordinarily strong at my location. This is further evidence of very good receiver design. There was no evidence of cross-modulation of KZZ47's signal by KEC63's signal, and I would anticipate the difference in signal level must be about 70-dB or more.

An excellent source of information about a particular weather radio station is the website

http://radiostationnet.com/weather/

RADIOSTATIONNET.COM have collected the exact transmitter location for NOAA Weather Radio stations and their transmitter power.

jimh posted 04-30-2013 11:47 AM ET (US)     Profile for jimh  Send Email to jimh     
The received signal level from KEC63 should be -21.3dBM, based on

Transmitter Power = 1,000-watts = +60dBm
Transmitter Line Loss = -1dB
Transmitter Antenna Gain = +6dB
Receive Antenna Gain = +5dB
Receive Line Loss = -1dB
Path Loss = -90.3dB

The received signal from KZZ47 should be around -97.7dBm, based on

Transmitter Power = 300-watts = +54.7dBm
Transmitter Line Loss = -1dB
Transmitter Antena Gain = +6dB
Receive Antenna Gain = +5dB
Receive Line Loss = -1dB
Path Loss = -162.4dB

The difference in signal levels is 76.4dB. That is an extremely large difference in signals for a spacing of only 0.025-Mhz, and indicates good receiver design.

Note: For the path loss of KEC63 I used a free-space model because the path is literally line-of-sight; I can indeed see the antenna. For the path loss of KZZ47 I used a model for loss of 40log(d) because the path is over the radio horizon and mostly an all-terrain path. These are reasonable assumptions.

jimh posted 11-15-2013 02:00 PM ET (US)     Profile for jimh  Send Email to jimh     
When I decommissioned my boat for the winter this year, I removed the boat's VHF Marine Band radio, a Standard-Horizon GX1500S. I did this not so much because I was worried about the radio sitting in the boat all winter, but rather to have the radio available on my bench for other uses. A few days ago I connected the GX1500S to my roof-mounted three-element vertically-polarized Yagi antenna, pointed at the Detroit River. This is the same antenna used in reporting to you all the signals I received as noted earlier in this thread of articles. I tuned around on the Weather Broadcast band with the GX1500S, and the results were very disappointing. Only three channels produced any sort of reception. This came as a surprise, as I had recalled receiving many more stations, as I noted in the previous entries here. Summarizing those results:

WX DX Summary

WX-1, 162.550-MHz: 3-miles, KEC63, Southfield Michigan
WX-2, 162.400-MHz: 80-miles, KHB97, Belleview, Ohio
WX-3, 162.475-MHz: 27-miles, VAZ533, Windsor, Ontario
WX-4, 162.425-Mhz: 104-miles, KXI94, Angola, Indiana
WX-5, 162.450-MHz: 59-miles, WNG647, Adrian, Michigan
WX-6, 162.500-MHz: 105-miles, WNG698, Grafton, Ohio
WX-7, 162.525-Mhz; 110-miles, KZZ47, Cary Ohio
WX-9, 161.775-MHz: 42-miles, VBE2, Leamington, Ontario

With the GX1500S only hearing a few stations, I began to wonder about its sensitivity. To make a test, I connected both the GX1500S and the earlier radio used, to the same antenna, using a very good quality antenna switch with excellent isolation to switch the antenna between the two radios. With this test set-up I could make instantaneous comparisons between the received signals from the various weather stations.

I was soon relieved to find that the GX1500S was working just fine, that is, it received any station the other receiver could hear, and, judging by ear the signal-to-noise ratio, the GX1500S might have a small advantage.

I see that I never did identify the other radio. It is an ICOM M402. This radio is probably ten years old. However, I don't have any doubts about its receiver sensitivity, as it was doing a great job pulling in all those NOAA and Canadian broadcasts.

The limited number of stations I could hear in this recent test is probably due to a general decline in the propagation conditions caused by the weather and other variables in propagation. In checking at various times in the last day or two, I have heard some weaker stations come and go.

I have observed that both radios seem to be limited in their receive on WX-8, 161.650-MHz. Both radios pick up an unmodulated weak carrier on that frequency. It may be some sort of localized interference.

jimh posted 09-29-2014 08:13 AM ET (US)     Profile for jimh  Send Email to jimh     
In some random use of my VHF Marine Band radio while connected to my rooftop antenna, I discovered that a considerable variation in received signals was caused by interference from a nearby DVD/CD player. When the DVD/CD player was powered on, it created noise interference in the VHF Marine Band radio receiver, and the sensitivity of the radio was degraded. This is a good example of how local noise sources can affect receiver sensitivity.

In testing a VHF Marine Band radio, it is prudent to begin by powering off all other electronic devices that are close by. Turn on each other electronic device, one at a time, and note if there is any increase in noise or reduced sensitivity in the VHF Marine Band radio receiver. It would not be surprising to find that other modern marine electronic devices, such as color screen chart plotters or high-power SONARs, might be generating some radio frequency noise that could affect radio receivers.

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