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Antenna Magic
A Ham buddy 's son just got his General ticket, and asked for my
assistance in making a surprise contact with his Dad for his first HF QSO. He had bought a nice 100W HF rig with an auto tuner, and an 40M-10M coax fed multi-band doublet antenna that was to be put in his attic initially. He lives about 100 miles from his Dad. I thought this was really cool, so I said I would set the whole thing up. Suggested 80M early evening for that distance would be best bet. He told me the auto tuner would not tune the 40-10 antenna on 80M (5to1 SWR). He then asked (here is the magic part) what he could do in 1 hour to get the antenna to tune on 80M. I told him to short the 40M loading coils, and add enough Home Depot wire to each end so that the auto tuner was happy. He had a 100' extension cord that he cut up and got the auto tuner happy 1.5 swr. At QSO time he could hear neither his dad or myself, and we gave up. Not to be discouraged he removed the shorts and additional wire, the tuner provided a 5:1 swr, and he had a nice QSO with his dad. He also stated he heard a lot more signals than before. Other than the obvious (he was mistaken in what he reported to me) any ideas as to what went wrong? I don't think he will ask for any more advice from me. Gary N4AST |
Antenna Magic
On Sun, 24 Jul 2011 15:52:08 -0700 (PDT), Gary
wrote: the tuner provided a 5:1 swr, and he had a nice QSO with his dad. He also stated he heard a lot more signals than before. Which goes to show that power is not necessary for communications. (If at 5:1, you are still getting half the power out into the Ęther. Let's call it 10:1 - that's still 30W out across 100 miles.) Nevermind the smoke. Other than the obvious (he was mistaken in what he reported to me) any ideas as to what went wrong? You mean the shorted coils and the extra wire? (Maybe he should have turned it off, and then back on again - Oops, standard IT advice.) Haven't a clue. I don't think he will ask for any more advice from me. Time will tell. 73's Richard Clark, KB7QHC |
Antenna Magic
On Sun, 24 Jul 2011 15:52:08 -0700 (PDT), Gary
wrote: Other than the obvious (he was mistaken in what he reported to me) any ideas as to what went wrong? You forgot to offer burnt offerings to the radio propagation gods. I don't think he will ask for any more advice from me. 80 meters at 100 miles is in the range of the NVIS propagation. 25 miles is about the limit for 80m ground wave, and 300 miles is about where sky wave starts. The problem with NVIS is that it's really picky about the height of the antenna above the ground. I don't have very much NVIS experience to offer any guaranteed suggestions on how to make NVIS work reliably. I assume the kid will be talking to his father regularly. My limited and unscientific tinkering empirically determined that the NVIS horizontal antenna wire has to be fairly close to the ground. A dipole that close to the ground has a fairly low impedance. See "height above ground" section: http://www.w0ipl.net/ECom/NVIS/nvis.htm My guess(tm) is that with the antenna near the ground, most of the RF goes straight up, which is what you want for NVIS, while an elevated antenna delivers more RF towards the horizon. There are plenty of web sites expounding on NVIS antenna and propagation worth reading. Tell the kid what you think happened, but let him do the research and tinkering. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Antenna Magic
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Antenna Magic
On Mon, 25 Jul 2011 05:56:43 +0000 (UTC), Owen Duffy
wrote: Next thing, someone will market a happiness meter, an SWR meter rebadged and rescaled with a percentage happiness factor. Sorry, but that would be prior art: http://cybraphon.com/process/the-emotion-meter/ http://www.flickr.com/photos/cybraphon/3789780162/in/pool-917701@N24/ http://en.wikipedia.org/wiki/E-meter I worked on something similar for the audiophile industry, when I invented an ambience and presence meter. Personally, methinks the correct solution for such technical problems is to virtualize everything and eliminate the antenna and radio: http://www.hamsphere.com http://qsonet.com/programs.html With these, you can have all the frustration of DX, without the expensive equipment and temperamental ionosphere. Do try to have a better day (as measured on the emotion meter). -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Antenna Magic
On 7/24/2011 6:52 PM, Gary wrote:
Not to be discouraged he removed the shorts and additional wire, His antenna worked better because he took his shorts off? - 73 de Mike N3LI - |
Antenna Magic
"Jeff Liebermann" wrote in message ... snip I worked on something similar for the audiophile industry, when I invented an ambience and presence meter. I was a Navy tech at a base in the Philippines in the early 1960s. Late one night (we were a 24-hour operation) with nothing much happening, one of the operators was in my shop, goofing with an ohmmeter. He picked it up and squeezed the leads, deflecting the needle some. I don't know what possessed me but I told him to press the leads to his temples. It deflected a bit more. I explained that he had less resistance in his head than in his whole body, and declared him "smart" for that reason. Well, he got the joke immediately and we laughed about it. However, it didn't stop him from parading a goodly number of the watch section into my shop for Intelligence Testing. Oh, my! "Sal" |
Antenna Magic
On Jul 25, 8:43*pm, Mike Coslo wrote:
On 7/24/2011 6:52 PM, Gary wrote: Not to be discouraged he removed the shorts and additional wire, His antenna worked better because he took his shorts off? * * * * - 73 de Mike N3LI - It never occurred to me that he would put his underware on the loading coils. I thought he would use some wire and jumper them. Mystery solved. Gary N4AST |
Antenna Magic
"Gary" wrote in message ... On Jul 25, 8:43 pm, Mike Coslo wrote: On 7/24/2011 6:52 PM, Gary wrote: Not to be discouraged he removed the shorts and additional wire, His antenna worked better because he took his shorts off? - 73 de Mike N3LI - It never occurred to me that he would put his underware on the loading coils. I thought he would use some wire and jumper them. Mystery solved. Gary N4AST ================================================== ==== When Gary had streched out the wire, For the signals he hoped to acquire, Big flames came along, 'Cause he did something wrong, And his boxers were lost in the fire. |
Antenna Magic
The modern explanation to modern hams is that an antenna tuner is there to keep the rig "happy". Modern folk are very busy people, they just don't have time for understanding, but personification of these inanimate things is apparently appealing. Your anecodote demonstrates though how inadequate that explanation is, whether happy rig or happy ATU. I understand your feeling that your pride has taken a bit of a dent. Well, part of the territory when predicting antennas eh! The whole idea was to get the Kid on the air, and excited about Ham Radio, by making his first HF QSO with his Dad. I think the learning will come later-he is a Patent Attorney-EE and Law degree. He impressed me Field Day when we were on an Island on a lake in South Carolina on 900 watt generator power. Had a lot of Impulse noise on RX even tho we were miles from power lines. Decided it was from the SMPS powering the Computer we were using for logging. The batteries on the Computer were good for ~1 hour, so we could not disconnect the SMPS for long. While we were fretting over what to do, he butchered up a spent beer can, and enclosed the SMPS, dropped the noise considerably, I was impressed. I hope he enjoys Ham Radio, in spite of my questionable advice. Gary N4AST |
Antenna Magic
On Tue, 26 Jul 2011 17:00:05 -0700 (PDT), Gary
wrote: I hope he enjoys Ham Radio, in spite of my questionable advice. Gary N4AST Think of the experience in a different way. If ham radio propagation were predictable and consistent, it would not be any fun. Just pickup the microphone, set the controls, and talk to anyone in the world. Kinda like a cell phone. It's the vaguarities of propagation, the magic of sub-optimal antennas, and the mysteries of operation that make ham radio fun. Considerable expense and effort, on the part of major players and governments, to obtain reliable HF communications has not been very successful over the years. Possibly "reliable HF" is an oxymoron. Welcome the "kid" to the magic part of ham radio and suggest that he adjust his expectations accordingly. Incidentally, I usually carry a folded wad of aluminum foil for improptu RFI/EMI shielding, probably because I don't drink beer. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Antenna Magic
On Jul 27, 10:48*am, Jeff Liebermann wrote:
On Tue, 26 Jul 2011 17:00:05 -0700 (PDT), Gary wrote: Incidentally, I usually carry a folded wad of aluminum foil for improptu RFI/EMI shielding, probably because I don't drink beer. Good comments Jeff, I will keep them in mind next time I talk to him. Too bad you don't drink beer, the "Learn by destroying" gets really easy after a couple. Or maybe it is just the destroying that gets easier. Gary N4AST |
Antenna Magic
On Wed, 27 Jul 2011 16:49:59 -0700 (PDT), Gary
wrote: Too bad you don't drink beer, the "Learn by destroying" gets really easy after a couple. Or maybe it is just the destroying that gets easier. Well, the slogan is not quite what it seems. I was graduation from Cal Poly Pomona back in the days when the skool slogan was "Learn By Doing". The basic education plan was to get as much hands on experience for the undergrads as possible. We modified the slogan to "Learn by Destroying" which had more than a little truth to it. I discovered quickly that the easiest way to understand how something works is to (accidentally) break it, and then desperately attempt to fix it before I'm discovered. It's a great way to learn, but does tend to get rather expensive. A less drastic version is sometimes called "sensitivity analysis" where one uses or installs a device in some manner in which it was never intended to function in an attempt to see how sensitive it is to installation and operation creativity. This works well with antennas, where there are almost an infinite number of ways to do it and still have it function. We have some local hams that have never removed the screws from their radios and looked inside. I often do this for them, while they complain about warranty and loss of resale value. Tearing the radio apart and giving them a tour of the guts (sometimes at radio club meetings) is also fun (to watch them sweat). You now have the unenviable task of acting as mentor to this new ham, who apparently has the potential for more than minimal understanding and knowledge. You may soon find yourself doing some furious reading (or Googling) in order to just keep up with him. I've done this a few times, where my usefulness eventually ends when the new ham tells me I don't know anything. I just smile, and await the next victim. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Antenna Magic
On 7/26/2011 6:44 AM, Gary wrote:
On Jul 25, 8:43 pm, Mike wrote: On 7/24/2011 6:52 PM, Gary wrote: Not to be discouraged he removed the shorts and additional wire, His antenna worked better because he took his shorts off? - 73 de Mike N3LI - It never occurred to me that he would put his underware on the loading coils. I thought he would use some wire and jumper them. Mystery solved. Gary N4AST He probably wet them first. John KD5YI |
Antenna Magic
On 7/28/2011 2:42 PM, John S wrote:
On 7/26/2011 6:44 AM, Gary wrote: On Jul 25, 8:43 pm, Mike wrote: On 7/24/2011 6:52 PM, Gary wrote: Not to be discouraged he removed the shorts and additional wire, His antenna worked better because he took his shorts off? - 73 de Mike N3LI - It never occurred to me that he would put his underware on the loading coils. I thought he would use some wire and jumper them. Mystery solved. Gary N4AST He probably wet them first. That's a time honored method of getting a better ground for your radials. - 73 de Mike N3LI - |
Antenna Magic
On 7/28/2011 12:31 PM, Jeff Liebermann wrote:
On Wed, 27 Jul 2011 16:49:59 -0700 (PDT), wrote: Too bad you don't drink beer, the "Learn by destroying" gets really easy after a couple. Or maybe it is just the destroying that gets easier. Well, the slogan is not quite what it seems. I was graduation from Cal Poly Pomona back in the days when the skool slogan was "Learn By Doing". The basic education plan was to get as much hands on experience for the undergrads as possible. We modified the slogan to "Learn by Destroying" which had more than a little truth to it. I discovered quickly that the easiest way to understand how something works is to (accidentally) break it, and then desperately attempt to fix it before I'm discovered. It's a great way to learn, but does tend to get rather expensive. A less drastic version is sometimes called "sensitivity analysis" where one uses or installs a device in some manner in which it was never intended to function in an attempt to see how sensitive it is to installation and operation creativity. This works well with antennas, where there are almost an infinite number of ways to do it and still have it function. We have some local hams that have never removed the screws from their radios and looked inside. I often do this for them, while they complain about warranty and loss of resale value. Tearing the radio apart and giving them a tour of the guts (sometimes at radio club meetings) is also fun (to watch them sweat). You now have the unenviable task of acting as mentor to this new ham, who apparently has the potential for more than minimal understanding and knowledge. You may soon find yourself doing some furious reading (or Googling) in order to just keep up with him. I've done this a few times, where my usefulness eventually ends when the new ham tells me I don't know anything. I just smile, and await the next victim. Ego suppression is a very useful tool! Mikek |
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