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#1
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On Fri, 19 Dec 2014 16:38:58 +0000, Channel Jumper
wrote: If you transmit a dead carrier and you don't say anything you are in fact violating the Part 97! As long as you identify yourself at the end of the transmission (and every 10 minutes), and not interfering with anyone, methinks it's legal. There's no lower limit on the speed of a CW transmission. Let's do the math for the MINIMUM Morse code speed: http://www.w8ji.com/cw_bandwidth_described.htm 1 / (0.002 WPM * 0.83 baud/wpm) = 602 seconds (10 mins) So, if I were experimenting with ultra narrow band long range Morse code or data transmission, that requires that I send very slowly, my MINIMUM speed would be 0.002 words per minute before one needs to identify. Disclaimer: I am not an attorney. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#2
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![]() "Channel Jumper" wrote in message ... Sorry Jeff, but you just shot yourself in the foot! If you transmit a dead carrier and you don't say anything you are in fact violating the Part 97! All you people did was reaffirm what I had already said. The sad fact is that we give out licenses like lolly pops at a barber shop with no real instruction involved and once a person gets a license they automatically think that they don't need to know the rules or anything that they learned to pass the exam to get the license. Had we had real Elmer's when we gave out those licenses, we wouldn't have 90% of the garbage we hear today on the HF radio! As far as amplifiers goes, yes I can see someone using a amplifier on 160 meters in the summertime, but the rest of the time, all they are doing is broadcasting - not really serving any purpose. If the OP bought a commercial OCFD in the first place - he wouldn't have these problems. The people that made comments about their OCFD out performing a center cut dipole for X frequency doesn't understand how a OCFD works. If you have a 80m OCFD and you use it on 10 meters, it acts like a 8 wavelength long 10m dipole. You actually get a realization of GAIN from the OCFD when you use it on 40 or 20 or 10m... Unfortunately in my book to realize gain you must give up something in one direction to improve your signal in another. So the term GAIN really isn't relevant here. Instead of using the term GAIN I should say improvement, because improvement would be a more relative term. Yes, I got my ham license out of the same Cracker Jack box that I got my First Class Phone license out of around 1972. The OCF I have is home built, but the blaun was bought. It does not take too much to add about 40 feet of wire to one side and 80 feet to the other side. The testing I did was on 80 meters around 2 or 3 in the afteroon. The band was almost dead, Not a signal within 50 khz of either side of where I was testing. I did ID and ask if the frequency was in useseveral times during the test. Ham radio is partly for testing and experminenting. That is what I was doing for about the 10 minuits total. You can look in the books and theory and everything else, but unless you put up several antennas and compair them in the same area like I have , it is all just a guess. The ground, trees,and atmosphere are almost impossiable to modle on a computer for every location. The OCF I was compairing was to an 80 meter dipole on 80 meters only, not other bands. Without being able to rotate an anenna, you have to take what you get as far as where the main lobe of the signal goes. Most of the ones that complain about amplifiers not being needed are the ones that don't have one,but wish they did. I seldom run one,but at times it does make a big differance in making good contacts and not. Same as with a beam. People with poor antennas say they can work all they can hear,but they do not realise they are not hearing much either. I don't knock people with poor antennas. At one time I did not have a very good antenna system either. Lived on a small lot without any trees and the best I could do was a dipole up about 20 feet. Still had fun with what I had. The name is real and the call is KU4PT, unlike some that post on here witout a real name or showing a call. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com |
#3
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On 12/19/2014 2:33 AM, Jeff wrote:
By changing the length of the coax you can make the antenna appear as being resonant or non resonant, even though the antenna may or may not be a perfect 50 ohm load. Incorrect, changing the length of the feeder will not change the SWR beyond any extra loss in the cable. It will change the phase of the mismatch that is all; (rotate around a constant VSWR circle on a Smith Chart). Jeff Incorrect. The basic VSWR meter measures the voltage, not the power. And if the SWR is other than 1:1, this voltage will change depending on the distance to the mismatch. Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms). But a shorted 1/4 wavelength coax shows an open (infinite impedance). Somewhere in between (I'm not going to bother to figure out exactly where because it's not that important) it will show an effective 50 ohm impedance. Coax length is unimportant when you have a 1:1 SWR, but if you don't, the coax will act as a matching network. And length will affect the overall system. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
#4
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On 12/19/2014 10:14 AM, Jerry Stuckle wrote:
On 12/19/2014 2:33 AM, Jeff wrote: By changing the length of the coax you can make the antenna appear as being resonant or non resonant, even though the antenna may or may not be a perfect 50 ohm load. Incorrect, changing the length of the feeder will not change the SWR beyond any extra loss in the cable. It will change the phase of the mismatch that is all; (rotate around a constant VSWR circle on a Smith Chart). Jeff Incorrect. The basic VSWR meter measures the voltage, not the power. And if the SWR is other than 1:1, this voltage will change depending on the distance to the mismatch. Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms). But a shorted 1/4 wavelength coax shows an open (infinite impedance). Somewhere in between (I'm not going to bother to figure out exactly where because it's not that important) it will show an effective 50 ohm impedance. Please bother. It is important to me to understand these things. And are you saying that there is a length of transmission line that will satisfy both the shorted and open conditions. What do you mean by "effective"? Are the lengths different in the two cases? Please help and thanks. Coax length is unimportant when you have a 1:1 SWR, but if you don't, the coax will act as a matching network. And length will affect the overall system. |
#5
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![]() "Jerry Stuckle" wrote in message ... On 12/19/2014 2:33 AM, Jeff wrote: By changing the length of the coax you can make the antenna appear as being resonant or non resonant, even though the antenna may or may not be a perfect 50 ohm load. Incorrect, changing the length of the feeder will not change the SWR beyond any extra loss in the cable. It will change the phase of the mismatch that is all; (rotate around a constant VSWR circle on a Smith Chart). Jeff # Incorrect. The basic VSWR meter measures the voltage, not the power. # And if the SWR is other than 1:1, this voltage will change depending on # the distance to the mismatch. But isn't it still Vmax over Vmin, regardless of where that happens on the feedline? # Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms). # But a shorted 1/4 wavelength coax shows an open (infinite impedance). # Somewhere in between (I'm not going to bother to figure out exactly # where because it's not that important) it will show an effective 50 ohm # impedance. # Coax length is unimportant when you have a 1:1 SWR, but if you don't, # the coax will act as a matching network. And length will affect the # overall system. I always understood the VSWR to be constant with the feedline length moving the parameters around the Smith chart constant VSWR circle. Thus it is possible by changing length to provide an antenna tuner with R and X values that the tuner can handle better. |
#6
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On 12/19/2014 12:10 PM, Wayne wrote:
"Jerry Stuckle" wrote in message ... On 12/19/2014 2:33 AM, Jeff wrote: By changing the length of the coax you can make the antenna appear as being resonant or non resonant, even though the antenna may or may not be a perfect 50 ohm load. Incorrect, changing the length of the feeder will not change the SWR beyond any extra loss in the cable. It will change the phase of the mismatch that is all; (rotate around a constant VSWR circle on a Smith Chart). Jeff # Incorrect. The basic VSWR meter measures the voltage, not the power. # And if the SWR is other than 1:1, this voltage will change depending on # the distance to the mismatch. But isn't it still Vmax over Vmin, regardless of where that happens on the feedline? Yes, but that changes along the coax, depending on the length from the mismatch. # Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms). # But a shorted 1/4 wavelength coax shows an open (infinite impedance). # Somewhere in between (I'm not going to bother to figure out exactly # where because it's not that important) it will show an effective 50 ohm # impedance. # Coax length is unimportant when you have a 1:1 SWR, but if you don't, # the coax will act as a matching network. And length will affect the # overall system. I always understood the VSWR to be constant with the feedline length moving the parameters around the Smith chart constant VSWR circle. Thus it is possible by changing length to provide an antenna tuner with R and X values that the tuner can handle better. No, VSWR is not constant along the length of the feedline. A transmission line connected to a load of a different impedance will act as an impedance transformer. The actual impedance at the source will be different than that at the load, depending on the load impedance, the transmission line impedance and the length of the transmission line. This is why changing the length of the coax allows the tuner to work better. Also since impedance is a function for the R and X values, when these change, the impedance changes. Yes, changing the length of the coax does move the parameters around the Smith chart in a circle, but it is not a constant VSWR circle. Plot it out and you will see the impedance changes, depending on the length of the coax. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
#7
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On 12/19/2014 10:14 AM, Jerry Stuckle wrote:
On 12/19/2014 2:33 AM, Jeff wrote: By changing the length of the coax you can make the antenna appear as being resonant or non resonant, even though the antenna may or may not be a perfect 50 ohm load. Incorrect, changing the length of the feeder will not change the SWR beyond any extra loss in the cable. It will change the phase of the mismatch that is all; (rotate around a constant VSWR circle on a Smith Chart). Jeff Incorrect. The basic VSWR meter measures the voltage, not the power. And if the SWR is other than 1:1, this voltage will change depending on the distance to the mismatch. Additionally, a shorted coax 1/2 wavelength long shows a short (0 ohms). But a shorted 1/4 wavelength coax shows an open (infinite impedance). Somewhere in between (I'm not going to bother to figure out exactly where because it's not that important) it will show an effective 50 ohm impedance. With a short, an open, or with what kind of load? Coax length is unimportant when you have a 1:1 SWR, but if you don't, the coax will act as a matching network. And length will affect the overall system. |
#8
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On Wednesday, December 17, 2014 6:34:22 PM UTC-6, Ralph Mowery wrote:
I have a home buit version of the Carolina Windom. An off center fed antenna about 120 feet long with a 4:1 voltage balun and from the feedpoint it goes to an inline ferrite bead choke 20 feet from the feed point, then 80 feet of rg-8 to the shack. The balun is suspose to be rated for 3 kw. It does have 2 cores in it. By tests, I know if I run ssb at over 800 watts the balun will heat up and change the swr. I have noticed lately that running just 100 watts ssb on 80 meters the swr seems to be going up to about 2:1 and the rig cuts the power back as expected as I talk from a starting point of 1:1. That has hapened for the last two mornings. I don't recall it doing that before. The antenna has been up for several years. It is just over 1:1 when normal on the frequency I most often operate on. Today in the afternoon when 80 meters was dead I transmitted a carrier for about 5 minuits and let off to ID, then another carrier for about 5 minuits and the swr did not change. Any ideas why the swr went up for the last two mornings, but did not seem to go up this afternoon ? Hard to say really, but sounds sort of moisture related.. Maybe moisture freezing, and then melting, or wet moisture that later dries out. Just a guess though.. If that balun warms up, it's adding a substantial amount of loss. Not really related to your problem, but I hate to see perfectly useful RF turn to heat. :| Also kind of verifies my theory of the cause of the loss I saw when using one of those antennas at a field day several years ago. I had compared it to a regular coax fed dipole, and it was way down from the dipole. I always blamed the voltage balun it used, and your experience sort of verifies that assumption. |
#9
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![]() wrote in message ... Hard to say really, but sounds sort of moisture related.. Maybe moisture freezing, and then melting, or wet moisture that later dries out. Just a guess though.. If that balun warms up, it's adding a substantial amount of loss. Not really related to your problem, but I hate to see perfectly useful RF turn to heat. :| Also kind of verifies my theory of the cause of the loss I saw when using one of those antennas at a field day several years ago. I had compared it to a regular coax fed dipole, and it was way down from the dipole. I always blamed the voltage balun it used, and your experience sort of verifies that assumption. While some of the RF is converted to heat, I also have a 80 meter dipole at the same height and at right angles to the OCF antenna. Switching back and forth between them, the OCF is usually beter. In a few cases the plane 80 mete dipole without a blun will work beter on 80 meters. Just a few months ago I hung an 18 and 24 MHz dipole about 6 inches bleow the 80 meter dipole and fed off the same coax. Still the OCF is usually beter. The ends of both antennas are about 50 to 60 feet off the ground and not suported in the middle or at the feed point. --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com |
#10
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On Thursday, December 18, 2014 5:05:35 PM UTC-6, Ralph Mowery wrote:
While some of the RF is converted to heat, I also have a 80 meter dipole at the same height and at right angles to the OCF antenna. Switching back and forth between them, the OCF is usually beter. In a few cases the plane 80 mete dipole without a blun will work beter on 80 meters. Just a few months ago I hung an 18 and 24 MHz dipole about 6 inches bleow the 80 meter dipole and fed off the same coax. Still the OCF is usually beter. The ends of both antennas are about 50 to 60 feet off the ground and not suported in the middle or at the feed point. I was thinking in terms of 80m. I suppose it's possible the windom could be better on some of the other bands. IE: a 80 dipole is not going to be too good on 40m unless you use a low loss method of feeding the high Z antenna. |
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