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Well, this crapped the bed.
- Thread starter C-pher
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cockpitbob
NES Member
Ditto. The initial surge was great, then we all slowed down. I wonder if it was a pan-flash or if Spring got us out of our shacks and away from the computers. I know I've been busy with taxes, a hunter safety class and Boy Scouts.
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I'm still around, I am reading the technician book right now. One hold up for me is having to have my address/call sign put on the internet. Something about doesn't strike me as right.
I might have to get a PO Box but it just seems like a waste of money to do that for what should be private information.
I might have to get a PO Box but it just seems like a waste of money to do that for what should be private information.
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I've been folllowing the threads but I have a little aprehension about posting too much radio info on a gun forum.
I think it would be great if we could all meet on HF since we then wouldn't need any repeaters/permission.
Over the last couple of weeks I've improved my station with an amp, better antenna tuner and I've been having some fun with the soldering iron. I've been saving a ton on jumpers and other small things. Got a semi functioning Daiwa 101swr/wattmeter from HRO in San Diego. Only $20!!! Took it apart, cleaned it up, tweaked it and now it functions like new. I put together a dummy load the other day that I figure is good for at least 1.25 kw (at least I hope so). I'm guessing I saved at least $50 by putting that together myself.
I would love to meet but the Spring market is keeping me busy. All my ham radio stuff is happening late at night.
I think it would be great if we could all meet on HF since we then wouldn't need any repeaters/permission.
Over the last couple of weeks I've improved my station with an amp, better antenna tuner and I've been having some fun with the soldering iron. I've been saving a ton on jumpers and other small things. Got a semi functioning Daiwa 101swr/wattmeter from HRO in San Diego. Only $20!!! Took it apart, cleaned it up, tweaked it and now it functions like new. I put together a dummy load the other day that I figure is good for at least 1.25 kw (at least I hope so). I'm guessing I saved at least $50 by putting that together myself.
I would love to meet but the Spring market is keeping me busy. All my ham radio stuff is happening late at night.
cockpitbob
NES Member
There. I just did my part by starting a new one that involves hunting and radios.
Now that the WX is a little better, I have fine tuned my Zepp to the point where it is the best antenna on my farm. I also put in some ground rods and also am about 3/4 of the way done building my new antanna tuner. When it is done, I was going to start a "homebrew" thread. I was also thinking about starting an "elmers" thread when I get some time. Realtor also has a point, I would prefer to get on HF with you guys.
ETA: Just think of this pause as a little QSB on the net![[smile]](/xen/styles/default/xenforo/smilies.vb/001.gif "Smile [smile]")
ETA: Just think of this pause as a little QSB on the net
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Well, I'm still having issues on figuring out how to hang my HF antenna as I don't have space for a tower and roter...or the money for a new vert G5 or G7.
Once I can get that worked out...I still need to drive in some Ground Rods...I should be able to get on HF.
Once I can get that worked out...I still need to drive in some Ground Rods...I should be able to get on HF.
Trees are your friend, I dont have anything holding my antennas up but trees. Wire antennas are inexpensive and unobtrusive. I have a mile of wire up in the air at my QTH and you would be hard pressed to see any of it unless it is pointed out to you.
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Agreed! I have a a box full of 'tools' for that very purpose. Including a small compound bow for the high stuff, a few spools of fishing line, a baseball with a small bridal attached for the lower stuff, several one hundred foot sections of black para cord etc. At first I was trying to put eye hooks up in the trees but I couldn't get those up high enough. Now I'm happy launching an arrow attached to the fishing line over a high limb. Then I attach the para cord to the fishing line and pull that up and over.
Lucas: I'm all for the homebrew thread. I can't wait to build something else. I have to assemble an antenna or two this coming weekend. I need something for 20m. I was going to do a dipole but I'm open to suggestions.
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Yep, but when I don't have the trees on my property is the issue on how to put my G5RV up in the air. I have some up...but where I would plan to put the one end would be a tree where all my electric, cable and phone are coming through.
So, I need to get some antenna pro's over to my house to walk around with me for some ideas.
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Cpher, for the time being you can simply support the middle and do an inverted V. That will work fairly well and buy you some time to think about a more permanent solution. My first setup had the middle of the antenna up about 25 feet and the ends were nearly touching the ground. It worked.
I thought that the ends needed to be at least 10 feet off the gound to prevent arcing. Is that not correct? I guess the first part is finding a place to put the middle where it's not overhead of my kids on the swingset. I don't have that large of a lot...that's my issue...and on the side of the house where it's coming out, there's not much in the way of hanging area...
Here are a few things I have learned over the years on wire antennas:
First of all, you dont need a "resonant antenna" to get efficiency, by designing the "system" properly, you can get excellent results. The optimum antennas are balanced types, non symetrical antenna systems relay on the lossy ground as part of the system. A perfectly balanced system does not require an "RF ground" however, I have yet to design a perfectly balanced antenna system no matter how hard I try so a good RF ground can only help the situation.
Use open wire feeder to minimize the losses due to SWR on the line, SWR is not necessarily bad if you use the correct feed line.
Use current baluns and not voltage baluns, current baluns are designed to drive equal current to each leg of the system and voltage baluns are designed to drive equal voltages into each leg of the system. You always want to strive for a current balance in the system, the voltage that develops due to the current is not of much concern.
There is nothing wrong with an inverted Vee configuration, In a properly tuned system, the major part of the radiation is at the center of the dipole which should be at a current maximum (voltage minimum) the ends of the antenna does not do much of the radiating so it is best to get the apex up as high as possible and deal with the ends as the land permits.
Contrary to popular belief, open wire feedline does not radiate RF if the system has electrical symmetry however, it will have much lower loss with a mismatched load. Coax on the other hand will have very high losses compared to open wire feedline with any mismatch. This is why the non resonant dipole fed with open wire line is so efficient, you can have a huge SWR say like 20:1 on the feedline and the losses will be negligable. One caveat is that a non resonant antenna system will require a tuner to match the wildly varying impedance at the input of the feedline to the transmitter output.
Most off the shelf tuners are unbalanced "T" networks feeding a 4:1 voltage baluns. This design goes back years and is not a very good one for several reasons. The worst offender is the 4:1 voltage balun at the tuner output. This device does not perform well with high SWR - Which is exactly what it will see if the tuner is doing its job. Due to the nature of its winding design, the voltage balun has strange impedance vs frequency characteristics. This will result in frequency dependent imbalances in the system which make it difficult to tune a system properly. Additionally, most "T" type networks work best into high impedances so why would you want to lower the impedance that the "T" network sees by a factor of 4? Inquiring minds want to know...
An alternative tuner design would be to put the balun at the input where it will always be operating at 50 ohms then the losses and impedances would be constant regardless of frequency. For the tuning network instead of using an unbalanced "T" network architecture, why not use a balanced "L" network that will preserve the symmetry of the system. You can directly connect the output of the balanced L network to a balanced feedline and match a far greater range of impedances than a T network. If you need to drive an unbalanced line for some reason, you can use another current balun at the output of the L network.
Coax feedlines are by definition unbalanced because they lack symmetry and the losses are much higher than open wire line due to its velocity factor. With a coax transmission line, you never want to have any current flowing on the outside of the shield. If you use a coax feed for a balanced antenna system, you should use a choke balun at the antenna end of the feedline. This will convert the unbalanced feed from the coax into a balanced feed that the antenna wants. If you use an unbalanced feedline without a balun, you will have current flowing on the outside of the shield. That will radiate and may get back into the shack so using coax as a balanced feedline will probably always cause you problems.
This balanced non resonant antenna system I have described has worked for me for years, I can get a match on any frequency I need to and it is very efficient. I have done experiments with RF ammeters in the station ground as well as in each leg of the balanced feedline and have verified that if the system is truely balanced (equal RF currents in the feedline) then the RF current in the station ground drops to zero but if I purposly unbalance the currents in the feedline then you can see the ground current rise.
For some reason, people prefer to use coax instead of open wire line. In addition to having much lower losses than coax, open wire line is much easier to get into the shack. I dont have any holes in my house for coax, I just run the open wire line into the window and close the window on it. it lies flat and comes right into the back of my tuner which is mounted right on the window sill, the entire tuner floats above ground (as it should).
First of all, you dont need a "resonant antenna" to get efficiency, by designing the "system" properly, you can get excellent results. The optimum antennas are balanced types, non symetrical antenna systems relay on the lossy ground as part of the system. A perfectly balanced system does not require an "RF ground" however, I have yet to design a perfectly balanced antenna system no matter how hard I try so a good RF ground can only help the situation.
Use open wire feeder to minimize the losses due to SWR on the line, SWR is not necessarily bad if you use the correct feed line.
Use current baluns and not voltage baluns, current baluns are designed to drive equal current to each leg of the system and voltage baluns are designed to drive equal voltages into each leg of the system. You always want to strive for a current balance in the system, the voltage that develops due to the current is not of much concern.
There is nothing wrong with an inverted Vee configuration, In a properly tuned system, the major part of the radiation is at the center of the dipole which should be at a current maximum (voltage minimum) the ends of the antenna does not do much of the radiating so it is best to get the apex up as high as possible and deal with the ends as the land permits.
Contrary to popular belief, open wire feedline does not radiate RF if the system has electrical symmetry however, it will have much lower loss with a mismatched load. Coax on the other hand will have very high losses compared to open wire feedline with any mismatch. This is why the non resonant dipole fed with open wire line is so efficient, you can have a huge SWR say like 20:1 on the feedline and the losses will be negligable. One caveat is that a non resonant antenna system will require a tuner to match the wildly varying impedance at the input of the feedline to the transmitter output.
Most off the shelf tuners are unbalanced "T" networks feeding a 4:1 voltage baluns. This design goes back years and is not a very good one for several reasons. The worst offender is the 4:1 voltage balun at the tuner output. This device does not perform well with high SWR - Which is exactly what it will see if the tuner is doing its job. Due to the nature of its winding design, the voltage balun has strange impedance vs frequency characteristics. This will result in frequency dependent imbalances in the system which make it difficult to tune a system properly. Additionally, most "T" type networks work best into high impedances so why would you want to lower the impedance that the "T" network sees by a factor of 4? Inquiring minds want to know...
An alternative tuner design would be to put the balun at the input where it will always be operating at 50 ohms then the losses and impedances would be constant regardless of frequency. For the tuning network instead of using an unbalanced "T" network architecture, why not use a balanced "L" network that will preserve the symmetry of the system. You can directly connect the output of the balanced L network to a balanced feedline and match a far greater range of impedances than a T network. If you need to drive an unbalanced line for some reason, you can use another current balun at the output of the L network.
Coax feedlines are by definition unbalanced because they lack symmetry and the losses are much higher than open wire line due to its velocity factor. With a coax transmission line, you never want to have any current flowing on the outside of the shield. If you use a coax feed for a balanced antenna system, you should use a choke balun at the antenna end of the feedline. This will convert the unbalanced feed from the coax into a balanced feed that the antenna wants. If you use an unbalanced feedline without a balun, you will have current flowing on the outside of the shield. That will radiate and may get back into the shack so using coax as a balanced feedline will probably always cause you problems.
This balanced non resonant antenna system I have described has worked for me for years, I can get a match on any frequency I need to and it is very efficient. I have done experiments with RF ammeters in the station ground as well as in each leg of the balanced feedline and have verified that if the system is truely balanced (equal RF currents in the feedline) then the RF current in the station ground drops to zero but if I purposly unbalance the currents in the feedline then you can see the ground current rise.
For some reason, people prefer to use coax instead of open wire line. In addition to having much lower losses than coax, open wire line is much easier to get into the shack. I dont have any holes in my house for coax, I just run the open wire line into the window and close the window on it. it lies flat and comes right into the back of my tuner which is mounted right on the window sill, the entire tuner floats above ground (as it should).
cockpitbob
NES Member
+1
nice post
nice post
You can hook a wire on a tuner, toss it out the window, and talk on HF. Just toss something up and go from there. My antenna is a dipole with the feed running up the side of my house, one leg strung over my back yard and tied to a tree, the other leg running through my attic vent, across my attic, then hangs down the inside wall. I've worked most of Europe, Canada, Central/South America, etc etc.
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Let me add a little to this. At that power level it would be wise to know absolutely yes or no. 1.25 kw is a lot of power when you are tuned for maximum smoke
Please be careful and ask for help if uncertain. The voltage for running legal limit WILL kill you. If you are one of the lucky ones with a solid state amp, the current they can draw will smoke anything undersized. Have fun and stay safe.
cockpitbob
NES Member
![[wink]](/xen/styles/default/xenforo/smilies.vb/002.gif "Wink [wink]")
Let me add a little to this. At that power level it would be wise to know absolutely yes or no. 1.25 kw is a lot of power when you are tuned for maximum smoke
at 1.25 KW into 50 ohms resistive you will have about 250 volts of RF across your load. If it doesn't kill you, it will hurt REAL bad. I would be more worried that if the load grenaded, the amp would be imediately unloaded and the voltage will get rediculously high and blow the crap out of the amplifier.
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I was thinking more along the line of the voltage inside a amp developing 1.25 kw. The only time I use a dummy load is to tune up.
Oh yeah, that too, if its a tube amp the plate supply is lethal be sure to use the one hand rule when ever the covers are off and use a shorting stick before touching anything. I think my SB201 runs about a 2.5 KV plate voltage and I shudder to think of how much current you could get out of it if you ever got across it. I know a few silent keys have met their end inside of an HF amp.
Got the mobile HF station up and running for a couple of weeks now and having an absolute ball, working ZL's and VK's almost everyday on the way home, tons of Europe and Asia, 20m has been amazing and this is only the beginning of the cycle! I am psyched!
Yes, things are getting exciting on HF, I have a regular sked with a guy out in Oregon and as recently as about a month ago, we were barely able to communicate with Olivia 16/500. Last week there was a big solar flare that wiped out the bands for about 2 days but ever since that event, the bands have been simply great. A few days after the flare, I was able to have the sked on 30 meters and we both had S-9 + signals for hours. We also both heard some very strange phenomenon during the QSO like very rapid QSB at about 3-4 Hertz. and some weird whistles. Yes, the solar cycle is indeed heating up!
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Hey you work Olivia, thats cool. I started working Olivia last year and love it. The S/N is even better than PSK. Speaking about power and voltage. I have a transformer for my amp that measures 14x8x12 and weighs about as much as a bad of portland cement. It does 1200,1800,7500,9500 at .8 amps![[shocked]](/xen/styles/default/xenforo/smilies.vb/007.gif "Shocked [shocked]")
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Let me add a little to this. At that power level it would be wise to know absolutely yes or no. 1.25 kw is a lot of power when you are tuned for maximum smoke
Well thanks for the concern. There are a some guys on the cop beating video thread that are probably hoping I get a jolt
I built a small cantenna. 5 resistors in parallel, 25 watts each. The resistors are soldered to two small boards and then wired to an so239 connector which is mounted on the lid of the paint can. The can is filled with mineral oil to help dissipate the heat. The resistors in air should handle 125 watts and so according to what I've read they should be able to handle about 10 times that in the oil. Of course I'm only talking key down for about 30 seconds max. On an ohm meter it measures 49.5 ohms. With my MFJ 259b it shows a 1:1 swr increasing slightly through 50 mhz When i get to VHF the swr is aprox 1.8:1. The one thing I did that goes against the theory is that i used ceramic insulated wire wound resistors. I'm supposed to use non inductive resistors but it's working ok.
I wanted to be able to tune my amp without polluting the bands. I'll try and get some photos but now that the can is filled with oil it may be a little messy.
ETA: My amp is capable of aprox. 800 watts pep. When I tune I'm running about 600-650 watts CW. The dummy load gets warm with a lot of use but not bad at all.
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Sounds like you got it right. Good job. Power handling as you have found out has a lot to do with time/heat. That should work fine tuning up. I should replace mine as I am sure the oil is full of pcb's. What kind of antenna are you using?
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I'm using a G5RV max. it's 204' long. Works great on the low bands and particularly on 40 meters but of course there's very little gain. I really want to get some better antennas but I'm not sure what I'll get first. I would love to build some kind of tri band beam. 8db of gain would be awesome!!
Thanks for the 'heads up' regarding the dummy load and the voltage. i really hadn't thought about it in those terms. Lucas is right. I did the math and i figure at 600 watts there's about 170 volts at 3.4 amps. That is enough to kill somebody. At 800 watts it;s closer to 200 volts at 4 amps
Thanks for the 'heads up' regarding the dummy load and the voltage. i really hadn't thought about it in those terms. Lucas is right. I did the math and i figure at 600 watts there's about 170 volts at 3.4 amps. That is enough to kill somebody. At 800 watts it;s closer to 200 volts at 4 amps
Yes, I have a regular sked with a guy I met back in my novice days. Due to the solar minimum over the last few years, we have had to go to olivia to keep in touch. We usually coordinate a frequency over email because we never really hear each others audio much but olivia is so good, you dont have to. The only problem is that since we are both running between 25-50 watts, other stations cant hear us so we get a lot of inadvertant QRM.Hey you work Olivia, thats cool. I started working Olivia last year and love it. The S/N is even better than PSK. Speaking about power and voltage. I have a transformer for my amp that measures 14x8x12 and weighs about as much as a bad of portland cement. It does 1200,1800,7500,9500 at .8 amps
I also generally use PSK-31 or RTTY and also SSTV.
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I listen to a few old timers on 20m during the day sometimes who used to work sstv in the late 60's. It is really cool listening to them talk about the old days. Like a window in to the past and I always feel inadequate when they start talking about the equipment they had to build for tv.
cockpitbob
NES Member
![[grin]](/xen/styles/default/xenforo/smilies.vb/041.gif "Grin [grin]")
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