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#1
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On 5/23/2011 5:10 PM, Wimpie wrote:
On 22 mayo, 20:04, 'Captain' Kirk wrote: I'm living in a wooded area and am trying to hit our club repeater reliably. It's cloudy now so I'm and getting a bit of ducting but I have a lot of trees, mostly poplars, in the direct path. I would have a line of sight if not for the trees as I'm up enough in altitude. I can cut the trees, they're mine, but finding the right ones is difficult and i don't want to waste the whole grove. I go from keying the repeater with no intelligible signal to not being able to hit it. Today I actually have an S meter reading due to the clouds. I am currently using a J-pole and will put up a Yagi soon but wonder if NVIS would work on 2m? I have only seen references to it being applied in HF. 'Captain' Kirk DeHaan N6SXR Hello, As you can see from the replies, we are in the speculation phase. If you would like to receive more specialized feedback, you should provide us with more details about the path, antenna height, nearby obstacles, vegetation in between, etc (maybe some pictures). As we are discussing 2 m wavelength, obstacles that may be optically in the path may introduce less attenuation then expected, but obstacles that are outside the optical path can still introduce attenuation. At 10m (33ft) from your antenna, the first Fresnel zone is about 9m (30 ft) wide. In addition, the tree attenuation at these frequencies is not that high. I think of 0.15 dB/m (I hope somebody can confirm this). It can be less due to diffraction (bending) of the waves around and over the trees. I am almost sure, removing some poplar treetops at 10m from your antenna or more will not change the situation from marginal to good (because of the relative low attenuation). Just to be curious, what type of poplar do you have at your site. With kind regards, Wim PA3DJS www.tetech.nl According to his lat/lon numbers, he is 19 miles from the repeater and its bearing is 185 degrees (ref true north) from him. The repeater is about 2000 feet above him (not including the tower height). He is in a valley that has little altitude variation until his signal reaches the mountain. This info is available from Google Earth using his numbers. All of this leads me to think that something else is wrong. I can hit a repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft tower. My antenna (half wave end-fed dipole) is on a 20 ft mast. I have tons of deciduous trees between me and the repeater but the signal is always solid with no noise on it (I don't have an S-meter) and I have never had a report of noise on my signal until I tried to carry on a conversation with 200 mw output power. Cheers, John |
#2
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On 24 mayo, 05:06, John KD5YI wrote:
On 5/23/2011 5:10 PM, Wimpie wrote: On 22 mayo, 20:04, 'Captain' Kirk wrote: I'm living in a wooded area and am trying to hit our club repeater reliably. *It's cloudy now so I'm and getting a bit of ducting but I have a lot of trees, mostly poplars, in the direct path. *I would have a line of sight if not for the trees as I'm up enough in altitude. *I can cut the trees, they're mine, but finding the right ones is difficult and i don't want to waste the whole grove. I go from keying the repeater with no intelligible signal to not being able to hit it. *Today I actually have an S meter reading due to the clouds. I am currently using a J-pole and will put up a Yagi soon but wonder if NVIS would work on 2m? *I have only seen references to it being applied in HF. 'Captain' Kirk DeHaan N6SXR Hello, As you can see from the replies, we are in the speculation phase. If you would like to receive more specialized feedback, you should provide us with more details about the path, antenna height, nearby obstacles, vegetation in between, etc (maybe some pictures). As we are discussing 2 m wavelength, obstacles that may be optically in the path may introduce less attenuation then expected, but obstacles that are outside the optical path can still introduce attenuation. At 10m (33ft) from your antenna, the first Fresnel zone is about 9m (30 ft) wide. In addition, the tree attenuation at these frequencies is not that high. I think of 0.15 dB/m (I hope somebody can confirm this). It can be less due to diffraction (bending) of the waves around and over the trees. I am almost sure, removing some poplar treetops at 10m from your antenna or more will not change the situation from marginal to good (because of the relative low attenuation). Just to be curious, what type of poplar do you have at your site. With kind regards, Wim PA3DJS www.tetech.nl According to his lat/lon numbers, he is 19 miles from the repeater and its bearing is 185 degrees (ref true north) from him. *The repeater is about 2000 feet above him (not including the tower height). *He is in a valley that has little altitude variation until his signal reaches the mountain. This info is available from Google Earth using his numbers. All of this leads me to think that something else is wrong. *I can hit a repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft tower. My antenna (half wave end-fed dipole) is on a 20 ft mast. I have tons of deciduous trees between me and the repeater but the signal is always solid with no noise on it (I don't have an S-meter) and I have never had a report of noise on my signal until I tried to carry on a conversation with 200 mw output power. Cheers, John Hello John, With Google maps, results (distance and bearing) are similar (based on the data given by Kirk). If the trees south of his antenna are the problem (I am not convinced), he needs to cut lots of them. They are about 150m from his antenna, and at that distance first Fresnel zone width is about 30m (100ft). It seems flat when looking to the activities in the valley. I hope somebody can make a path profile and loss simulation to see what is the real obstacle. With kind regards, Wim PA3DJS |
#3
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Wimpie said the following on 5/24/2011 6:47 AM:
On 24 mayo, 05:06, John wrote: On 5/23/2011 5:10 PM, Wimpie wrote: On 22 mayo, 20:04, 'Captain' Kirk wrote: I'm living in a wooded area and am trying to hit our club repeater reliably. It's cloudy now so I'm and getting a bit of ducting but I have a lot of trees, mostly poplars, in the direct path. I would have a line of sight if not for the trees as I'm up enough in altitude. I can cut the trees, they're mine, but finding the right ones is difficult and i don't want to waste the whole grove. I go from keying the repeater with no intelligible signal to not being able to hit it. Today I actually have an S meter reading due to the clouds. I am currently using a J-pole and will put up a Yagi soon but wonder if NVIS would work on 2m? I have only seen references to it being applied in HF. 'Captain' Kirk DeHaan N6SXR Hello, As you can see from the replies, we are in the speculation phase. If you would like to receive more specialized feedback, you should provide us with more details about the path, antenna height, nearby obstacles, vegetation in between, etc (maybe some pictures). As we are discussing 2 m wavelength, obstacles that may be optically in the path may introduce less attenuation then expected, but obstacles that are outside the optical path can still introduce attenuation. At 10m (33ft) from your antenna, the first Fresnel zone is about 9m (30 ft) wide. In addition, the tree attenuation at these frequencies is not that high. I think of 0.15 dB/m (I hope somebody can confirm this). It can be less due to diffraction (bending) of the waves around and over the trees. I am almost sure, removing some poplar treetops at 10m from your antenna or more will not change the situation from marginal to good (because of the relative low attenuation). Just to be curious, what type of poplar do you have at your site. With kind regards, Wim PA3DJS www.tetech.nl According to his lat/lon numbers, he is 19 miles from the repeater and its bearing is 185 degrees (ref true north) from him. The repeater is about 2000 feet above him (not including the tower height). He is in a valley that has little altitude variation until his signal reaches the mountain. This info is available from Google Earth using his numbers. All of this leads me to think that something else is wrong. I can hit a repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft tower. My antenna (half wave end-fed dipole) is on a 20 ft mast. I have tons of deciduous trees between me and the repeater but the signal is always solid with no noise on it (I don't have an S-meter) and I have never had a report of noise on my signal until I tried to carry on a conversation with 200 mw output power. Cheers, John Hello John, With Google maps, results (distance and bearing) are similar (based on the data given by Kirk). If the trees south of his antenna are the problem (I am not convinced), he needs to cut lots of them. They are about 150m from his antenna, and at that distance first Fresnel zone width is about 30m (100ft). I was up on my neighbors property along the path to the repeater and the quantity of trees is a lot more than I had remembered. Since this is tree growing/logging country it is not feasible for me to be cutting huge amounts of trees. The deciduous can go but there are to many conifers on both properties to cut just for signal. You are correct on the distance to the grove and it is the, I believe, the only impediment. It seems flat when looking to the activities in the valley. I hope somebody can make a path profile and loss simulation to see what is the real obstacle. I download the Radio Mobile SW that someone suggested but am still trying to figure out how to use it. With kind regards, Wim PA3DJS -- 'Captain' Kirk DeHaan N6SXR "Beam me up Scotty, there's no intelligent life here" |
#4
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On Tue, 24 May 2011 08:17:46 -0700, 'Captain' Kirk DeHaan
wrote: I download the Radio Mobile SW that someone suggested but am still trying to figure out how to use it. Radio-Mobile will give you the expected coverage area and signal strengths from your location. However, it's a tricky program to master and will require some patience and practice. There are tutorials. For example: http://www.pizon.org/radio-mobile-tutorial/index.html http://www.bcwireless.net/moin.cgi/RadioMobile/Tutorial http://radiomobile.pe1mew.nl/ etc. Also check YouTube for various video tutorials. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#5
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On 5/24/2011 8:47 AM, Wimpie wrote:
On 24 mayo, 05:06, John wrote: On 5/23/2011 5:10 PM, Wimpie wrote: On 22 mayo, 20:04, 'Captain' Kirk wrote: I'm living in a wooded area and am trying to hit our club repeater reliably. It's cloudy now so I'm and getting a bit of ducting but I have a lot of trees, mostly poplars, in the direct path. I would have a line of sight if not for the trees as I'm up enough in altitude. I can cut the trees, they're mine, but finding the right ones is difficult and i don't want to waste the whole grove. I go from keying the repeater with no intelligible signal to not being able to hit it. Today I actually have an S meter reading due to the clouds. I am currently using a J-pole and will put up a Yagi soon but wonder if NVIS would work on 2m? I have only seen references to it being applied in HF. 'Captain' Kirk DeHaan N6SXR Hello, As you can see from the replies, we are in the speculation phase. If you would like to receive more specialized feedback, you should provide us with more details about the path, antenna height, nearby obstacles, vegetation in between, etc (maybe some pictures). As we are discussing 2 m wavelength, obstacles that may be optically in the path may introduce less attenuation then expected, but obstacles that are outside the optical path can still introduce attenuation. At 10m (33ft) from your antenna, the first Fresnel zone is about 9m (30 ft) wide. In addition, the tree attenuation at these frequencies is not that high. I think of 0.15 dB/m (I hope somebody can confirm this). It can be less due to diffraction (bending) of the waves around and over the trees. I am almost sure, removing some poplar treetops at 10m from your antenna or more will not change the situation from marginal to good (because of the relative low attenuation). Just to be curious, what type of poplar do you have at your site. With kind regards, Wim PA3DJS www.tetech.nl According to his lat/lon numbers, he is 19 miles from the repeater and its bearing is 185 degrees (ref true north) from him. The repeater is about 2000 feet above him (not including the tower height). He is in a valley that has little altitude variation until his signal reaches the mountain. This info is available from Google Earth using his numbers. All of this leads me to think that something else is wrong. I can hit a repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft tower. My antenna (half wave end-fed dipole) is on a 20 ft mast. I have tons of deciduous trees between me and the repeater but the signal is always solid with no noise on it (I don't have an S-meter) and I have never had a report of noise on my signal until I tried to carry on a conversation with 200 mw output power. Cheers, John Hello John, With Google maps, results (distance and bearing) are similar (based on the data given by Kirk). If the trees south of his antenna are the problem (I am not convinced), he needs to cut lots of them. They are about 150m from his antenna, and at that distance first Fresnel zone width is about 30m (100ft). It seems flat when looking to the activities in the valley. I hope somebody can make a path profile and loss simulation to see what is the real obstacle. With kind regards, Wim PA3DJS Well, I have applied some numbers today and I am changing my mind that the trees are not the problem. If my numbers are correct: The repeater, 19 miles away, is 1900 feet above his elevation. At that distance, the antenna will appear be about 240 feet lower than actual due to earth curvature. That makes the antenna appear to be about 0.954 degrees above the horizon. That is equivalent to 60 feet at 3600 feet. In other words, 60 foot trees closer in will be completely in the way. The hurtful part of this is that his antenna at 45 feet will have a lowest angle of radiation (take-off angle) of .7 degrees, right into the near trees. The next lobe above that is at 2.2 degrees. Between those two lobes is a null. In short, I think his antenna is in a null. I think the only answer for his present situation is to raise the antenna another 10 feet. What do you think? 73, John |
#6
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On 4 jun, 23:26, John S wrote:
On 5/24/2011 8:47 AM, Wimpie wrote: On 24 mayo, 05:06, John *wrote: On 5/23/2011 5:10 PM, Wimpie wrote: On 22 mayo, 20:04, 'Captain' Kirk wrote: I'm living in a wooded area and am trying to hit our club repeater reliably. *It's cloudy now so I'm and getting a bit of ducting but I have a lot of trees, mostly poplars, in the direct path. *I would have a line of sight if not for the trees as I'm up enough in altitude. *I can cut the trees, they're mine, but finding the right ones is difficult and i don't want to waste the whole grove. I go from keying the repeater with no intelligible signal to not being able to hit it. *Today I actually have an S meter reading due to the clouds. I am currently using a J-pole and will put up a Yagi soon but wonder if NVIS would work on 2m? *I have only seen references to it being applied in HF. 'Captain' Kirk DeHaan N6SXR Hello, As you can see from the replies, we are in the speculation phase. If you would like to receive more specialized feedback, you should provide us with more details about the path, antenna height, nearby obstacles, vegetation in between, etc (maybe some pictures). As we are discussing 2 m wavelength, obstacles that may be optically in the path may introduce less attenuation then expected, but obstacles that are outside the optical path can still introduce attenuation. At 10m (33ft) from your antenna, the first Fresnel zone is about 9m (30 ft) wide. In addition, the tree attenuation at these frequencies is not that high. I think of 0.15 dB/m (I hope somebody can confirm this). It can be less due to diffraction (bending) of the waves around and over the trees. I am almost sure, removing some poplar treetops at 10m from your antenna or more will not change the situation from marginal to good (because of the relative low attenuation). Just to be curious, what type of poplar do you have at your site. With kind regards, Wim PA3DJS www.tetech.nl According to his lat/lon numbers, he is 19 miles from the repeater and its bearing is 185 degrees (ref true north) from him. *The repeater is about 2000 feet above him (not including the tower height). *He is in a valley that has little altitude variation until his signal reaches the mountain. This info is available from Google Earth using his numbers. All of this leads me to think that something else is wrong. *I can hit a repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft tower. My antenna (half wave end-fed dipole) is on a 20 ft mast. I have tons of deciduous trees between me and the repeater but the signal is always solid with no noise on it (I don't have an S-meter) and I have never had a report of noise on my signal until I tried to carry on a conversation with 200 mw output power. Cheers, John Hello John, With Google maps, results (distance and bearing) are similar (based on the data given by Kirk). If the trees south of his antenna are the problem (I am not convinced), he needs to cut lots of them. *They are about 150m from his antenna, and at that distance first Fresnel zone width is about 30m (100ft). It seems flat when looking to the activities in the valley. I hope somebody can make a path profile and loss simulation to see what is the real obstacle. With kind regards, Wim PA3DJS Well, I have applied some numbers today and I am changing my mind that the trees are not the problem. If my numbers are correct: The repeater, 19 miles away, is 1900 feet above his elevation. At that distance, the antenna will appear be about 240 feet lower than actual due to earth curvature. That makes the antenna appear to be about 0.954 degrees above the horizon. That is equivalent to 60 feet at 3600 feet. In other words, 60 foot trees closer in will be completely in the way. The hurtful part of this is that his antenna at 45 feet will have a lowest angle of radiation (take-off angle) of .7 degrees, right into the near trees. The next lobe above that is at 2.2 degrees. Between those two lobes is a null. In short, I think his antenna is in a null. I think the only answer for his present situation is to raise the antenna another 10 feet. What do you think? 73, John Hello John, This link: http://www.tetech.nl/divers/Kirk_Repeater_USA_1.png shows the path profiles with and without trees (from Radio Mobile, VE2DBE). I will keep it there for some weeks. I used 30m (98ft) high trees (so they are easy to see). The trees cover some additional part of the first fresnel zone, but the average canopy will be lower and the absorption loss is not that high at 146 MHz. So yes, there is influence from the trees, but not that much I think. If you want to get some increase in signal, you need to remove lots of them, and he don't want to do that. Note that the first trees are 160m away from his antenna (info from google earth, based on data provided by Kirk). With kind regards, Wim PA3DJS www.tetech.nl |
#7
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On 6/4/2011 6:20 PM, Wimpie wrote:
On 4 jun, 23:26, John wrote: On 5/24/2011 8:47 AM, Wimpie wrote: Well, I have applied some numbers today and I am changing my mind that the trees are not the problem. If my numbers are correct: The repeater, 19 miles away, is 1900 feet above his elevation. At that distance, the antenna will appear be about 240 feet lower than actual due to earth curvature. That makes the antenna appear to be about 0.954 degrees above the horizon. That is equivalent to 60 feet at 3600 feet. In other words, 60 foot trees closer in will be completely in the way. The hurtful part of this is that his antenna at 45 feet will have a lowest angle of radiation (take-off angle) of .7 degrees, right into the near trees. The next lobe above that is at 2.2 degrees. Between those two lobes is a null. In short, I think his antenna is in a null. I think the only answer for his present situation is to raise the antenna another 10 feet. What do you think? 73, John Hello John, This link: http://www.tetech.nl/divers/Kirk_Repeater_USA_1.png shows the path profiles with and without trees (from Radio Mobile, VE2DBE). I will keep it there for some weeks. I used 30m (98ft) high trees (so they are easy to see). The trees cover some additional part of the first fresnel zone, but the average canopy will be lower and the absorption loss is not that high at 146 MHz. So yes, there is influence from the trees, but not that much I think. If you want to get some increase in signal, you need to remove lots of them, and he don't want to do that. Note that the first trees are 160m away from his antenna (info from google earth, based on data provided by Kirk). With kind regards, Wim PA3DJS www.tetech.nl In that case, perhaps it is due to his antenna being at a height that puts the target into a null. Along with low repeater output power, I suppose that could cause it. Thanks, Wim. 73, John - KD5YI |
#8
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On 6/5/2011 10:59 AM, John S wrote:
On 6/4/2011 6:20 PM, Wimpie wrote: On 4 jun, 23:26, John wrote: On 5/24/2011 8:47 AM, Wimpie wrote: Well, I have applied some numbers today and I am changing my mind that the trees are not the problem. If my numbers are correct: The repeater, 19 miles away, is 1900 feet above his elevation. At that distance, the antenna will appear be about 240 feet lower than actual due to earth curvature. That makes the antenna appear to be about 0.954 degrees above the horizon. That is equivalent to 60 feet at 3600 feet. In other words, 60 foot trees closer in will be completely in the way. The hurtful part of this is that his antenna at 45 feet will have a lowest angle of radiation (take-off angle) of .7 degrees, right into the near trees. The next lobe above that is at 2.2 degrees. Between those two lobes is a null. In short, I think his antenna is in a null. I think the only answer for his present situation is to raise the antenna another 10 feet. What do you think? 73, John Hello John, This link: http://www.tetech.nl/divers/Kirk_Repeater_USA_1.png shows the path profiles with and without trees (from Radio Mobile, VE2DBE). I will keep it there for some weeks. I used 30m (98ft) high trees (so they are easy to see). The trees cover some additional part of the first fresnel zone, but the average canopy will be lower and the absorption loss is not that high at 146 MHz. So yes, there is influence from the trees, but not that much I think. If you want to get some increase in signal, you need to remove lots of them, and he don't want to do that. Note that the first trees are 160m away from his antenna (info from google earth, based on data provided by Kirk). With kind regards, Wim PA3DJS www.tetech.nl In that case, perhaps it is due to his antenna being at a height that puts the target into a null. Along with low repeater output power, I suppose that could cause it. Thanks, Wim. 73, John - KD5YI Okay. I take that back. I just ran a simulation with EZNEC and it shows twice as much uV available at the receiver than Radio Mobile, so my conclusion is that a pattern null is not involved. I'm stumped. 73, John |
#9
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John KD5YI said the following on 5/23/2011 8:06 PM:
On 5/23/2011 5:10 PM, Wimpie wrote: On 22 mayo, 20:04, 'Captain' Kirk wrote: I'm living in a wooded area and am trying to hit our club repeater reliably. It's cloudy now so I'm and getting a bit of ducting but I have a lot of trees, mostly poplars, in the direct path. I would have a line of sight if not for the trees as I'm up enough in altitude. I can cut the trees, they're mine, but finding the right ones is difficult and i don't want to waste the whole grove. I go from keying the repeater with no intelligible signal to not being able to hit it. Today I actually have an S meter reading due to the clouds. I am currently using a J-pole and will put up a Yagi soon but wonder if NVIS would work on 2m? I have only seen references to it being applied in HF. 'Captain' Kirk DeHaan N6SXR Hello, As you can see from the replies, we are in the speculation phase. If you would like to receive more specialized feedback, you should provide us with more details about the path, antenna height, nearby obstacles, vegetation in between, etc (maybe some pictures). As we are discussing 2 m wavelength, obstacles that may be optically in the path may introduce less attenuation then expected, but obstacles that are outside the optical path can still introduce attenuation. At 10m (33ft) from your antenna, the first Fresnel zone is about 9m (30 ft) wide. In addition, the tree attenuation at these frequencies is not that high. I think of 0.15 dB/m (I hope somebody can confirm this). It can be less due to diffraction (bending) of the waves around and over the trees. I am almost sure, removing some poplar treetops at 10m from your antenna or more will not change the situation from marginal to good (because of the relative low attenuation). Just to be curious, what type of poplar do you have at your site. With kind regards, Wim PA3DJS www.tetech.nl According to his lat/lon numbers, he is 19 miles from the repeater and its bearing is 185 degrees (ref true north) from him. The repeater is about 2000 feet above him (not including the tower height). He is in a valley that has little altitude variation until his signal reaches the mountain. This info is available from Google Earth using his numbers. All of this leads me to think that something else is wrong. I can hit a repeater 20 miles from me with 5 Watts and its antenna is on a 300 ft tower. My antenna (half wave end-fed dipole) is on a 20 ft mast. There may well be something wrong with the antenna. I don't have an SWR meter handy but will try and borrow one from a club member. The J-pole was beat around quite a bit over the years but since the radio has a limiting circuit if the SWR is too far out of whack I am assuming it is fairly close. It will transmit of full power. I'm using 75' of professionally assembled RG8X which is required to get from the radio to the antenna. I have tons of deciduous trees between me and the repeater but the signal is always solid with no noise on it (I don't have an S-meter) and I have never had a report of noise on my signal until I tried to carry on a conversation with 200 mw output power. Not to make light, one of these poplars is tons in itself. They are easily 70' tall and 24" diameter. I truly appreciate all the help from everyone. Cheers, John -- 'Captain' Kirk DeHaan N6SXR "Beam me up Scotty, there's no intelligent life here" |
#10
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On Tue, 24 May 2011 08:24:09 -0700, 'Captain' Kirk DeHaan
wrote: There may well be something wrong with the antenna. I don't have an SWR meter handy but will try and borrow one from a club member. The J-pole was beat around quite a bit over the years but since the radio has a limiting circuit if the SWR is too far out of whack I am assuming it is fairly close. It will transmit of full power. The American Legion J-pole is rather critical, especially the dual band flavor. The vertical section of electrical wire between the coax connector and the part where it's wound around the driven element is the tuning adjustment. Move it slightly and it's mistuned. You'll need a VSWR meter to re-tune it. I'm using 75' of professionally assembled RG8X which is required to get from the radio to the antenna. RX-8x is 4.5dB loss per 100ft. Half your power is being lost in the coax. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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