Posted: 10/10/2011 9:05:36 AM EDT
As a n00b to the HF world (ok HAM in general  ) I think something that would be a great topic and save a few headaches down the road is if you more seasoned guys tell what kind of reliable HF comms you have in your area. Now I do know enough to know some days 1k watts and a beam wont hit the side of a barn and on other days a wet string and 5w will get you around the world. Just as an example; from the center of Texas I can usually talk up to southern Kansas on 20m, or 80m NVIS in my area is getting me about a 300mile coverage. Also what do the seasons do to those bands? This comes from the numerous topics of guys wanting to talk across their state with FRS radios. Maybe if there were a reference that people could go back to and see what bands do in their area they may have a better Idea of what they want to do with Amateur radio.
As a disclaimer VHF and UHF radios (2m, 1.25m, 70cm the radios you buy at walmart and marine radios all fall into this category) are LOS or line of sight. So pretty much they will only go as far as you can see. Now if you are on top of a mountain this greatly improves the range (that's why repeaters are usually placed at higher elevations). HF is OTH or over the horizon meaning that it "bounces" back and forth between the atmosphere and ground. The time of day, season, and sun all have a play in how this is effected. For more information Look up AR-Jedi's articles or Google "propagation" Well let the bragging begin |
no braggin-I'm a  too
but I started out with hopes of accomplishing NVIS (10-500 miles) here at the farm, and I've done just that My HF rig is a Kenwood TS-50, a 100 watt Mobile/Base unit from days gone by. I purchased this unit for it's reputation of solid performance and ease of use. HF Radio Selection Thread I use a 75' "Random Wire" antenna fed by a LDG 4:1 Balun. The Antenna is strung about 8' in the air with a complimenting counterpoise running parallel on the top of the ground. The negative feed from the Balun is tied to a ground rod, and the counterpoise is connected there as well. The wire used is from Home Depot-bought on a 500' roll. 14ga IIRC. AFRCOM random wire thread As I look back into my QRZ log; I see that for me, in Upstate (Northwest) SC 80 Meters and 40 Meters work best for NVIS. It's worked all-over as well (Mexico, Spain, Italy, Slovenia, etc...) Last night I got to Kansas on 20 Meters..so go figure. As mentioned above, the variables multiply each time you blink. YMMV eta: speeling |
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Quoted:
As a n00b to the HF world (ok HAM in general ) I think something that would be a great topic and save a few headaches down the road is if you more seasoned guys tell what kind of reliable HF comms you have in your area. Now I do know enough to know some days 1k watts and a beam wont hit the side of a barn and on other days a wet string and 5w will get you around the world. Just as an example; from the center of Texas I can usually talk up to southern Kansas on 20m, or 80m NVIS in my area is getting me about a 300mile coverage. Also what do the seasons do to those bands? This comes from the numerous topics of guys wanting to talk across their state with FRS radios. Maybe if there were a reference that people could go back to and see what bands do in their area they may have a better Idea of what they want to do with Amateur radio.
As a disclaimer VHF and UHF radios (2m, 1.25m, 70cm the radios you buy at walmart and marine radios all fall into this category) are LOS or line of sight. So pretty much they will only go as far as you can see. Now if you are on top of a mountain this greatly improves the range (that's why repeaters are usually placed at higher elevations). HF is OTH or over the horizon meaning that it "bounces" back and forth between the atmosphere and ground. The time of day, season, and sun all have a play in how this is effected. For more information Look up AR-Jedi's articles or Google "propagation" Well let the bragging begin i can tell you that VHF is not LOS unless yout talking HT to HT. and its not LOS because of something you should have learned about called the "radio horizon" which is actually farther than the actual visual horizon. 180 miles is well over my visual horizon but i have talked that far more than once when propagation was up. |
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As a n00b to the HF world (ok HAM in general ) I think something that would be a great topic and save a few headaches down the road is if you more seasoned guys tell what kind of reliable HF comms you have in your area. Now I do know enough to know some days 1k watts and a beam wont hit the side of a barn and on other days a wet string and 5w will get you around the world. Just as an example; from the center of Texas I can usually talk up to southern Kansas on 20m, or 80m NVIS in my area is getting me about a 300mile coverage. Also what do the seasons do to those bands? This comes from the numerous topics of guys wanting to talk across their state with FRS radios. Maybe if there were a reference that people could go back to and see what bands do in their area they may have a better Idea of what they want to do with Amateur radio.
As a disclaimer VHF and UHF radios (2m, 1.25m, 70cm the radios you buy at walmart and marine radios all fall into this category) are LOS or line of sight. So pretty much they will only go as far as you can see. Now if you are on top of a mountain this greatly improves the range (that's why repeaters are usually placed at higher elevations). HF is OTH or over the horizon meaning that it "bounces" back and forth between the atmosphere and ground. The time of day, season, and sun all have a play in how this is effected. For more information Look up AR-Jedi's articles or Google "propagation" Well let the bragging begin i can tell you that VHF is not LOS unless yout talking HT to HT. and its not LOS because of something you should have learned about called the "radio horizon" which is actually farther than the actual visual horizon. 180 miles is well over my visual horizon but i have talked that far more than once when propagation was up. I understand that a VHF SSB can cover hundreds of miles with the correct conditions. But if you have gone out and bought a SSB radio then you probably know that. In general VHF/UHF radios are LOS. I can use a 2m HT and a yagi to talk 35 miles which is past my visual horizon as well, however I don't plan on that as reliable comms with that radio. Example I can talk to a repeater 35mi away but I cant activate the IRLP node using my DTMF tones. That post and this thread is meant to be a generilization thread, you said yourself that the only way you talked 180miles was when propagation was up. |
| no, VHF FM can get you well over the visual horizon. thats what i was using to talk 180 miles. i can regularly talk 50+ miles with my IC-2800 and NR770 mounted in my truck. as i said, HT's might be LOS but mobiles and even base stations can get out much farther than LOS. i have yet to work 2m SSB even though my HF radio has it built in. with 2 5w HT's and a better antenna that the stock duck you should be getting 4 miles depending on terrain and buildings. with that same NR770 and my 5w HT a friend and i(he has the same antenna but different HT) talked appx 7 miles with no problems. with my FT-100 and a role up J pole i was able to talk 15-18 miles with the antenna mounted on one of those "command hooks" on the wall of my single story house with full signal. the general rule is 1mile per watt, give or take, depending on conditions and whats around you and the person your talking to. |
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VHF and UHF signals travel in a straight line. This is called line-of-sight propagation. This limits operating distance in many areas. Sometimes hills and buildings interfere with the signals. Even without obstructions, VHF and UHF signals won't travel much further than the horizon. In order to increase operating distances at these frequencies, ham operators started using devices called repeaters.
Link to ARRL pdf on VHF/UHF |
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Europe on 20-25 w PSK31... Italy, Spain, Switzerland, Azores, Canary Islands, Central and South America, all the way to the tip end of Argentina.
Phone, England, Ireland, all over Canada, coast to coast in the USA, Central and South America with 100 w SSB on 20, 17, and 15 meters. At night, on 75 meters, with 500-600 watts (Ameritron AL-811H) I've talked 1100-1200 mile radius around my QTH, depending on propagation. |
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VHF and UHF signals travel in a straight line. This is called line-of-sight propagation. This limits operating distance in many areas. Sometimes hills and buildings interfere with the signals. Even without obstructions, VHF and UHF signals won't travel much further than the horizon. In order to increase operating distances at these frequencies, ham operators started using devices called repeaters. Link to ARRL pdf on VHF/UHF that "much farther than the horizon" is just that, the radio horizon. thank you for proving my point. actually, to increase that distance all you have to do is move your antenna higher. |
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Europe on 20-25 w PSK31... Italy, Spain, Switzerland, Azores, Canary Islands, Central and South America, all the way to the tip end of Argentina. Phone, England, Ireland, all over Canada, coast to coast in the USA, Central and South America with 100 w SSB on 20, 17, and 15 meters. At night, on 75 meters, with 500-600 watts (Ameritron AL-811H) I've talked 1100-1200 mile radius around my QTH, depending on propagation. i only do SSB but even with voice i have talked all over Europe, not been so lucky inside the US though. of course im limited with time i can be on the radio and antenna space but for what i got, im impressed. |
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VHF and UHF signals travel in a straight line. This is called line-of-sight propagation. This limits operating distance in many areas. Sometimes hills and buildings interfere with the signals. Even without obstructions, VHF and UHF signals won't travel much further than the horizon. In order to increase operating distances at these frequencies, ham operators started using devices called repeaters. Link to ARRL pdf on VHF/UHF that "much farther than the horizon" is just that, the radio horizon. thank you for proving my point. actually, to increase that distance all you have to do is move your antenna higher. You just said that there is nothing between you and the bird that is LOS! Also my quote from the article said "won't travel much further than the horizon". So that is not OTH. One other thing, by moving your antenna higher you are increasing your LOS. thank you for proving my points. |
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your forgetting about the antenna the bird has. its not just about YOUR equipment. What about the antenna the bird has? If its a HT floating in space you can still talk to it as long as you have a clear line of sight. If VHF is OTH I guess we can get rid of all the useless 2m repeaters. I understand that VHF/UHF can be affected by atmospheric conditions. But VHF/UHF is not going to act the same as HF. If you want to remind me of my Tech exam I'll remind you of something called MUF maximum usable frequency and LUF lowest usable frequency. These are the variables that affect radio signal propagation. HF is HF because it bounces off the atmosphere back to earth. VHF/UHF is higher then the MUF this is what lets it travel through the atmosphere and to the satellites in space. There is no magic antenna on a satellite, look at pics of the AO51 you will see a small wire sticking out the top. not some 5/8 wave J-pole. it doesn't need much because it has LOS to the earth. |
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The whole LOS stuff is hooey. There are many things that factor into this equasion. I'll agree that if you were on fairly flat land you won't get much further than the "radio horizon" (which is typically 15% more than the physical horizon) but when you go to a real world situation the whole LOS edict goes right out the window. Here in AZ, I can talk from my work back into town about 15 miles. That seems easy huh? Then consider there is a mountain range between my work and town. LOS rule goes out the window. VHF/UHF can and will reflect off of mountains and buildings. There is also "knife edge" propogation to consider. People take the whole LOS thing too literally IMO.
OP, reliable HF comms locally can be challenging. Night time NVIS on 40 or 80m is your best bet but you will have a zone from where your ground wave stops and the reflected NVIS signal starts that you won't be able to contact no matter how much power you run. My plan would be to run 10m during the day with beams and power. Night ops on 40 or 80m NVIS and power if required. Winter is best for the lower bands 40 80 160m as we are further from the sun and it's effect. Higher bands in the summer eg:17 15 12 10m. |
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The whole LOS stuff is hooey. There are many things that factor into this equasion. I'll agree that if you were on fairly flat land you won't get much further than the "radio horizon" (which is typically 15% more than the physical horizon) but when you go to a real world situation the whole LOS edict goes right out the window. Here in AZ, I can talk from my work back into town about 15 miles. That seems easy huh? Then consider there is a mountain range between my work and town. LOS rule goes out the window. VHF/UHF can and will reflect off of mountains and buildings. There is also "knife edge" propogation to consider. People take the whole LOS thing too literally IMO. OP, reliable HF comms locally can be challenging. Night time NVIS on 40 or 80m is your best bet but you will have a zone from where your ground wave stops and the reflected NVIS signal starts that you won't be able to contact no matter how much power you run. My plan would be to run 10m during the day with beams and power. Night ops on 40 or 80m NVIS and power if required. Winter is best for the lower bands 40 80 160m as we are further from the sun and it's effect. Higher bands in the summer eg:17 15 12 10m. Thanks KB7DX. So as a honest question why is it being taught as LOS? My home town is in a mountain valley and we depend on repeaters in the area to get "out" of the valley. If you talk through a mountain and I can not talk through a mountain how can that be a property of the band? I'm not saying that VHF/UHF is as LOS as a laser beam (sorry if it came out that way) but that it is not a OTH band. |
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To get back to the OP's original question...
Ordinarily NVIS comm's is pretty reliable, meaning 8 times out of 10 you can make contact. However it is far less so for hams because we are forced to make large jumps between HF frequencies. With 100W and a low dipole you can reliably make contacts from between 100 and 500 miles away but it depends on how close maximum usable frequency (MUF) is the the ham band you are using, the closer the better but not below the band. So even NVIS, supposedly very reliable, can be a crapshoot for hams. In my particular case it's open every once in a while on 40 and once in a great while on 80 in the summer, in winter very reliably on 80 in 4 hours after sundown in the evening and 160M other than that. As for DX reliability if you are a digital user it is easy to figure that out. Just hit the PSK31 spots on each band and see what stations are up. In 5 minutes you can see 30 or 40 call signs and determine where that band will be open for you for any mode, digital, CW or voice. My east coast low dipole regularly works DX into Europe during east coast grayline hours and, to a lesser extent, stations west to the Mississippi. It also for some reason works 20 well into northern South America. 30 sometimes works, 40 is a total crapshoot for me. |
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Quoted: To get back to the OP's original question... Ordinarily NVIS comm's is pretty reliable, meaning 8 times out of 10 you can make contact. However it is far less so for hams because we are forced to make large jumps between HF frequencies. With 100W and a low dipole you can reliably make contacts from between 100 and 500 miles away but it depends on how close maximum usable frequency (MUF) is the the ham band you are using, the closer the better but not below the band. So even NVIS, supposedly very reliable, can be a crapshoot for hams. In my particular case it's open every once in a while on 40 and once in a great while on 80 in the summer, in winter very reliably on 80 in 4 hours after sundown in the evening and 160M other than that. As for DX reliability if you are a digital user it is easy to figure that out. Just hit the PSK31 spots on each band and see what stations are up. In 5 minutes you can see 30 or 40 call signs and determine where that band will be open for you for any mode, digital, CW or voice. My east coast low dipole regularly works DX into Europe during east coast grayline hours and, to a lesser extent, stations west to the Mississippi. It also for some reason works 20 well into northern South America. 30 sometimes works, 40 is a total crapshoot for me. To add to this info: For reliable NVIS, one needs to have a basic understanding of the Maximum Useable Frequency, MUF, and the critical frequency. This is pretty good info: https://www.txarmymars.org/downloads/NVIS-Theory-and-Practice.pdf and this is a good little cheat-sheet: https://www.txarmymars.org/downloads/SolarWeatherCheatSheet.pdf |
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For 40 m and 80 m, most ham's antennas are already NVIS... it's hard to get an 80 m antenna up 1/2 wavelength above the ground. That would be 120' or more. And few get their 40 m antenna up 1/2 wavelength... somewhat over 60'.
So, if your antenna is 35' via a pushup pole... well, it's NVIS. 
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