Receiver Testing with NOAA Weather Radio Broadcasts
Posted: Fri Jun 01, 2018 10:09 am
Note: this article is an updated version of one that appeared in the old forum. I am reposting it to the new forum so that further updates can be appended to it. The tests described below took place in March and April of 2013--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. The radio is an older ICOM M402. The antenna is a three-element yagi mounted about 20-feet above ground and pointed southeast toward the Detroit River. The antenna is a directional antenna and has some gain, perhaps 5 dBd, but all of the paths to NOAA stations are over mostly urban terrain. On a boat at sea, the paths will be mostly over water, and a good receiver and antenna should be able to obtain similar reception at similar distances. 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/coverage/site2.php?State=OH&Site=KHB97
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
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.
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.
Checking the weather signals a few days later, 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.
Here is a link to a Google Maps plot of 1,013 NOAA Weather Radio transmitter sites:
NOAA Weather Radio Transmitter Sites
https://www.google.com/maps/d/viewer?mid=100vLnERm-RPnR6kpEG1EEyfq9ys&usp=sharing
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 your receiver for the purpose of assessing the path length.
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. The radio is an older ICOM M402. The antenna is a three-element yagi mounted about 20-feet above ground and pointed southeast toward the Detroit River. The antenna is a directional antenna and has some gain, perhaps 5 dBd, but all of the paths to NOAA stations are over mostly urban terrain. On a boat at sea, the paths will be mostly over water, and a good receiver and antenna should be able to obtain similar reception at similar distances. 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/coverage/site2.php?State=OH&Site=KHB97
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
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.
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.
Checking the weather signals a few days later, 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.
Here is a link to a Google Maps plot of 1,013 NOAA Weather Radio transmitter sites:
NOAA Weather Radio Transmitter Sites
https://www.google.com/maps/d/viewer?mid=100vLnERm-RPnR6kpEG1EEyfq9ys&usp=sharing
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 your receiver for the purpose of assessing the path length.