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#91
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4NEC2?
On 15/10/2018 20:42, Roger Hayter wrote:
wrote: Roger Hayter wrote: You say "none of us" - there are only three of you! Most group users don't particularly love Reay and his acolytes much more than Spike, I would think. I'd **** on Burt if he weren't on fire. Does that make you feel better, Rog? I'd also put a dog dirt through his letterbox. Quite so. But there are still only three of you. What did we do to deserve such tedious windbags? -- Spike "Nearly all men can stand adversity, but if you want to test a man's character, give him an internet group to manage" |
#92
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4NEC2?
On Tue, 16 Oct 2018 14:18:56 +0000
Spike wrote: On 15/10/2018 20:42, Roger Hayter wrote: wrote: Roger Hayter wrote: You say "none of us" - there are only three of you! Most group users don't particularly love Reay and his acolytes much more than Spike, I would think. I'd **** on Burt if he weren't on fire. Does that make you feel better, Rog? I'd also put a dog dirt through his letterbox. Quite so. But there are still only three of you. What did we do to deserve such tedious windbags? Burt, you spent years of your life on Usenet being a horrible ****, Burt. Burt, Thanks, Burt. |
#93
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4NEC2?
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#94
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4NEC2?
On Tue, 16 Oct 2018 07:44:53 +0000, Spike
wrote: Very interesting, but I'd have to say that none of what you say refutes my original contention that the distant station, which after all is the one we are trying to communicate with, will notice any difference to the received signal whether the sending station's antenna was tuned with a 20c torch bulb or a $300 VNA. You touched on the main vagaries of the system when you said "What I've found is that such side by side comparisons do not account for variations in propagation, path, interference, local noise, time of day, position of the moon, and other factors beyond the operators control". Perhaps an analogy might be useful. Instead of an HF radio, you're dealing with your automobile. Under normal circumstances, it will get you to work and back fairly efficiently. However, you notice that your gasoline (petrol) mileage is not quite what you might expect. So, you have a choice of mechanics. The first mechanic tunes the engine with a light bulb, divining rod, magic incantations, and offers a rather bizarre description of what work was done on the vehicle. The second mechanic uses proper computerized test equipment to analyze the situation, uses factory parts, and delivers the car with a detailed printout of what was done, what changes were made, what parts were used, and a before-after gas mileage comparison performed on a dynamometer. Now, which mechanic would you prefer? Your car will still go to work and back in some manner. The second mechanic will cost more, because he has to pay for all the expensive equipment and genuine parts. If you're impoverished, obviously the first mechanic will be the only available choice, but assuming you plan to keep the vehicle, one might suspect it is a bad long term solution. From my perspective, both professional and as a ham, I deal in numbers. I can tell by looking at the numbers what is happening and what needs to be done. I have a small collection of aging test equipment to help me generate the numbers. Light bulbs do not generate numbers and are therefore (in my never humble opinion) useless and worthless. However, I will concede that if your intent is "to be able to transmit signals intended to be received by another station", a light bulb is sufficient to determine that your transmitter is spewing RF, spurs, harmonics, and noise into an antenna-like device that is either radiating the RF, absorbing it into heat, or reflecting it back to the transmitter (because the light bulb indicates the same in both directions). -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#96
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4NEC2?
On Tue, 16 Oct 2018, Spike wrote:
On 16/10/2018 09:14, Jeff wrote: A common way of generating both usb and lsb was to have 2 switched crystals with frequencies just above and below 9MHz in the oscillator, feeding a balanced mixer, before the xtal filter, and switch depending on which sideband you required. Is there a mathematician on here that can explain the maths of sideband inversion/retention? No inversion is required with this method. If you feed a ~9MHz signal and audio into a balanced mixer the output will be both sidebands plus a suppressed carrier. Your xtal filter is ~2.4kHz wide centred on 9MHz, so if you move the frequency of the ~9Mhz signal (switch a crystal) going into the balanced mixer either above or below 9MHz you can select which side band goes through your filter. Simples. Wasn't a similar system used in the Yaesu FT-200 (9MHz IF, 5 MHz VFO)? IIRC the set had a NORM/INV sideband switch. That wasn't uncommon, the conversion scheme allowing for the "default" sideband to be one switch position, so the only time you needed to switch sidebands was if you needed the "wrong" sideband". Michael |
#97
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4NEC2?
On Tue, 16 Oct 2018 13:22:28 -0400, Ralph Mowery
wrote: Again, it all depends on the mechanic. The computer tune may only get you a small improvement and it will take 5 years to make up the cost difference. I had a car that started running real bad. After the simple things I replaced like spark plugs, wires and coil, I looked on an Autozone page and one thing was a $ 500 sensor that may cause the problem. I took it to a dealer that should have all the proper equipment. After about 3 weeks he finally replaced that sensor and it fixed the problem. The part would have taken less than half an hour to replace. They may still have been working on it if I had not sent off a nice email to Toyota after a week and a half of no repair. I know of a case where a Freeze plug was leaking and the motor company wanted to pull the engine to get to it. Shade tree mechanic pulled back the carpet inside the car, took a hole saw and cut a hole in the firewall to get to the plug. Repaired the hole with a beer can and pop rivits for less than $ 100. All that you've shown is that an idiot with all the technology of modern electronics can screw things up, and that simple repairs can be done simply and cheaply by someone who has some experience. I'm talking about a given situation, which could be done with either a light bulb or a pile of test equipment. Not two different repair situations. So, let's take your blown $500 black box, presumably out of warranty. Would you take the problem to the shade tree mechanic with his beer can and pop rivet tool? What would you expect him to do? Drill open the black box and start replacing parts until it works? Would he offer a warranty? At best, he would find a similar black box at a scrap yard, box rebuider, or midnight auto, and sell it to you at a discount. Would you consider that acceptable? Let me bring it closer to home. You purchased an expensive HF radio with all the bells and whistles. It's out of warranty and you need something fixed. Would you send it to 1) the factory, 2) an authorized repair station, 3) a rebuilder in China, 4) the ham equivalent of the shade tree mechanic, or 5) the teenager next door? The distinction between these choices is a experience and training, but also access to the necessary test equipment and parts. Better yet, if you knew any of these used a light bulb to determine if your transmitter was working, and a "talk test" as QA, would you do business with them? No need to answer the questions. Just think about the implications. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#98
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4NEC2?
On 16/10/2018 14:38, Ralph Mowery wrote:
In article , lid says... Very interesting, but I'd have to say that none of what you say refutes my original contention that the distant station, which after all is the one we are trying to communicate with, will notice any difference to the received signal whether the sending station's antenna was tuned with a 20c torch bulb or a $300 VNA. You touched on the main vagaries of the system when you said "What I've found is that such side by side comparisons do not account for variations in propagation, path, interference, local noise, time of day, position of the moon, and other factors beyond the operators control". Sometimes it is who is doing the adjusting and not how good the equipment is. That's very true, of course. Some good equipment is in the 'wrong hands'. Almost 40 years ago I started keeping a repeater on the air that was started by someone else. My test equipment at that time was a VTVM, a $ 25 Heathkit signal generator, old Oscilloscope, swr meter, and frequency counter. To tune the receiver my best 'signal generator' was a ham near the edge of the repeater coverage. I would have him just to key down for a minute or two at a time while I adjusted the receiver. Over the years a better receiver and transmitter was installed. Now I have some very good test equipment, but can not say the coverage of the repeater is very much better. What little improvement is made is probably because the radio equipment is better. Thanks! That's just the sort of thing I was on about - in this case you actually used a distant station to help with the set-up, and it worked well. At that time one thing I did not try to adjust or check was the duplexer as I did not think I could with what I had to work with. Many years ago the tuning instructions for duplexers was to tune for maximum signal on the pass and best rejection. As test equipment became better and priced in range, the pass tuning change to using a return loss bridge and SA/TG. This seems to work much better. I found the pass was broad and you could usually give the tuning rod a turn or two without much effect, but he RLB shows up in less than 1/2 of a turn. Does it make a difference ? Probably not in effective coverage (it may extend the range a foot or two,hi), but at least I know it tuned the best it can be with what I have to work with. One thing that does come with better test equipment is knowing that the equipment is tuned so it meets or exceeds the specifications. Before it was just a guess as if the equipment did or did not meet specifications. Quite so. But 'specifications' are often written with other things in mind - compatibility, spurii, stability, etc, and not necessarily anything at all to do with how the distant station receives/perceives one's signal. -- Spike "Nearly all men can stand adversity, but if you want to test a man's character, give him an internet group to manage" |
#99
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4NEC2?
On 16/10/2018 20:47, Jeff Liebermann wrote:
Let me bring it closer to home. You purchased an expensive HF radio with all the bells and whistles. It's out of warranty and you need something fixed. Would you send it to 1) the factory, 2) an authorized repair station, 3) a rebuilder in China, 4) the ham equivalent of the shade tree mechanic, or 5) the teenager next door? If you send to anyone other than yourself then you are not a real radio ham or radio amateur. A CBer, probably. |
#100
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4NEC2?
On 16/10/2018 16:17, Jeff Liebermann wrote:
On Tue, 16 Oct 2018 07:44:53 +0000, Spike wrote: Very interesting, but I'd have to say that none of what you say refutes my original contention that the distant station, which after all is the one we are trying to communicate with, will notice any difference to the received signal whether the sending station's antenna was tuned with a 20c torch bulb or a $300 VNA. You touched on the main vagaries of the system when you said "What I've found is that such side by side comparisons do not account for variations in propagation, path, interference, local noise, time of day, position of the moon, and other factors beyond the operators control". Perhaps an analogy might be useful. Instead of an HF radio, you're dealing with your automobile. Under normal circumstances, it will get you to work and back fairly efficiently. However, you notice that your gasoline (petrol) mileage is not quite what you might expect. So, you have a choice of mechanics. The first mechanic tunes the engine with a light bulb, divining rod, magic incantations, and offers a rather bizarre description of what work was done on the vehicle. The second mechanic uses proper computerized test equipment to analyze the situation, uses factory parts, and delivers the car with a detailed printout of what was done, what changes were made, what parts were used, and a before-after gas mileage comparison performed on a dynamometer. Now, which mechanic would you prefer? Your car will still go to work and back in some manner. The second mechanic will cost more, because he has to pay for all the expensive equipment and genuine parts. If you're impoverished, obviously the first mechanic will be the only available choice, but assuming you plan to keep the vehicle, one might suspect it is a bad long term solution. From my perspective, both professional and as a ham, I deal in numbers. I can tell by looking at the numbers what is happening and what needs to be done. I have a small collection of aging test equipment to help me generate the numbers. Light bulbs do not generate numbers and are therefore (in my never humble opinion) useless and worthless. They don't need to generate numbers! I can think of at least one method, using light bulbs, that will get a pretty accurate measurement of power, and if you want, balance, in a system. The distant station, of course, knows nothing of this, and couldn't tell whether I'd used the 'numbers' of your method or the analogue approach of mine. However, I will concede that if your intent is "to be able to transmit signals intended to be received by another station", a light bulb is sufficient to determine that your transmitter is spewing RF, spurs, harmonics, and noise into an antenna-like device that is either radiating the RF, absorbing it into heat, or reflecting it back to the transmitter (because the light bulb indicates the same in both directions). But the people your imaginary friend works for care for none of this, as his car gets him to work on time. To bring this back to the issue at hand, I claimed that "I'd have to say that none of what you say refutes my original contention that the distant station, which after all is the one we are trying to communicate with, will notice any difference to the received signal whether the sending station's antenna was tuned with a 20c torch bulb or a $300 VNA" and so far that still stands. -- Spike "Nearly all men can stand adversity, but if you want to test a man's character, give him an internet group to manage" |
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