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ATU: Correct way to specify impedance range
ve2pid wrote:
Hi to all, Just got my new ATU. The specs mentionned: Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about 3:1) It sems that this is the standardized (?) way to mention specifications... But, since impedances have both a resistive and reactive compoment, doses it means 6 to 600 Ohms "resistive"? For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms.. Thanks de Pierre Only the manufacturer can tell you what they mean. It would be interesting to see what they say when you ask. Roy Lewallen, W7EL |
ATU: Correct way to specify impedance range
ve2pid wrote:
Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about 3:1) I once emailed a tuner company (don't recall which) and asked them about their specs. They told me that their ohmic specs were for resistive loads. They didn't say where one would find an antenna with a 600+j0 feedpoint impedance - maybe a 4-wire folded dipole? -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
ATU: Correct way to specify impedance range
On May 21, 7:28*am, ve2pid wrote:
Hi to all, Just got my new ATU. The specs mentionned: Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about 3:1) It sems that this is the standardized (?) way to mention specifications... But, since impedances have both a resistive and reactive compoment, doses it means 6 to 600 Ohms "resistive"? For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms.. Thanks de Pierre It would be good if they plotted the range on something like a Smith chart. It should be done for different frequencies; it's rare indeed for a tuner to be able to match the same range of impedances over its frequency range. Some tuner topologies even have "holes" in their coverage. Icing on the cake would be some additional lines on the Smith charts showing the expected power loss, perhaps as constant-loss contour lines. Many (most? all?) tuners get pretty lossy at some adjustments. As far as I know, none of the ham manufacturers do that. I expect it, though, for commercial equipment, and we ought to hold the ham manufacturers' feet to the fire to do something similar. Cheers, Tom |
ATU: Correct way to specify impedance range
K7ITM wrote:
... we ought to hold the ham manufacturers' feet to the fire to do something similar. I suspect their average amateur radio customer doesn't understand the meaning of 1000+j1000 much less comprehend graphs on a Smith Chart. I recently published an article over on eHam.net that contained a Smith Chart. One of the reactions was that Smith Charts are obsolete and have been replaced by software programs that just provide the answers without all the effort and pain involved with understanding a Smith Chart. One doesn't need to know anything about hyperbolic trig functions any more. Just point and click. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
ATU: Correct way to specify impedance range
On 21 mayo, 19:41, Cecil Moore wrote:
K7ITM wrote: ... we ought to hold the ham manufacturers' feet to the fire to do something similar. I suspect their average amateur radio customer doesn't understand the meaning of 1000+j1000 much less comprehend graphs on a Smith Chart. I recently published an article over on eHam.net that contained a Smith Chart. One of the reactions was that Smith Charts are obsolete and have been replaced by software programs that just provide the answers without all the effort and pain involved with understanding a Smith Chart. One doesn't need to know anything about hyperbolic trig functions any more. Just point and click. -- 73, Cecil, IEEE, OOTC, *http://www.w5dxp.com Hello Cecil, I was expecting that this only happens in the Netherlands. I have some (modern) software where the default plot method is Schmit Chart... I agree with the contour plot on a Smith Chart showing losses (and power handling) for Antenna Tuners. Best regards, Wim PA3DJS www.tetech.nl forget first three letters of the alphabet in the PM |
ATU: Correct way to specify impedance range
On Thu, 21 May 2009 07:28:25 -0700 (PDT), ve2pid
wrote: Hi to all, Just got my new ATU. The specs mentionned: Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about 3:1) It sems that this is the standardized (?) way to mention specifications... But, since impedances have both a resistive and reactive compoment, doses it means 6 to 600 Ohms "resistive"? For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms.. Thanks de Pierre Well, a little Googleing found the missing maker and model number. It's obviously made by LDG but which product? http://www.ldgelectronics.com The spec sheets aren't any more useful. I'm also rather suspicious because ALL their products, regardless of size or technology, have the same specification. Well, if all else fails, I guess I have to read one of the manuals: http://www.ldgelectronics.com/assets/manuals/Z-817Manual.pdf No help in the Theory of Operation section. The manual has a slightly expanded specification: "Tunes 6 to 600 ohm loads (16 to 150 on 6M), 24 to 2400 ohms with optional 4:1 Balun." My guess(tm) is that they're refering to the vector sum of the complex impedance, which is what one ends up measuring on a VSWR guess-meter. Disclaimer: This is only a guess. As for the proper way to specify antenna tuners, I vaguely recall a marine band antenna tuner that we sold at Intech in the 1970's. (Not my project). The matching range was specified as anything that landed inside a constant VSWR circle on a Smith Chart and was limited to a conservate 8:1 VSWR range. It also excluded any resonant antennas, which would automatically fall outside of the 10:1 range. We also derrated the maximum power handling spec at the 1.6MHz end to avoid high voltage flash over. I'll dig through my box of old Intech data sheets and manuals later and see what I can excavate. Meanwhile, call LDG and ask. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
ATU: Correct way to specify impedance range
K7ITM wrote:
On May 21, 7:28Â*am, ve2pid wrote: Hi to all, Just got my new ATU. The specs mentionned: Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about 3:1) It sems that this is the standardized (?) way to mention specifications... But, since impedances have both a resistive and reactive compoment, doses it means 6 to 600 Ohms "resistive"? For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms.. Thanks de Pierre It would be good if they plotted the range on something like a Smith chart. It should be done for different frequencies; it's rare indeed for a tuner to be able to match the same range of impedances over its frequency range. Some tuner topologies even have "holes" in their coverage. Icing on the cake would be some additional lines on the Smith charts showing the expected power loss, perhaps as constant-loss contour lines. Many (most? all?) tuners get pretty lossy at some adjustments. As far as I know, none of the ham manufacturers do that. I expect it, though, for commercial equipment, and we ought to hold the ham manufacturers' feet to the fire to do something similar. Cheers, Tom SGC used to publish the capacitance and inductance range of their tuners from which you could calculate what it would do at a specific frequency. I haven't looked in a long time so I don't know if it is still there. -- Jim Pennino Remove .spam.sux to reply. |
ATU: Correct way to specify impedance range
...; it's rare indeed
for a tuner to be able to match the same range of impedances over its frequency range. Some tuner topologies even have "holes" in their coverage. This is why it is so pointless to specify the resistive SWR range. It is really only an indication. If your antenna system winds up with an impossible match at some frequency, you need to try something different anyway or suffer loss or damage. Hope the autotuner algorithm knows how to deal with that. There was a QST test review years ago that compared several popular tuners. Old and new. |
ATU: Correct way to specify impedance range
On May 21, 11:30*am, wrote:
.... I was expecting that this only happens in the Netherlands. *I have some (modern) software where the default plot method is Schmit Chart... I agree with the contour plot on a Smith Chart showing losses (and power handling) for Antenna Tuners. Best regards, Wim PA3DJSwww.tetech.nl forget first three letters of the alphabet in the PM Since the points plotted on a Smith chart are simply complex reflection coefficient plotted on a linear grid, it would be fine with me if they'd just plot the range of complex reflection coefficient over which the tuner will operate (perhaps plus contours of constant loss and power handling ability). The graphs would look identically the same, except for the grid. I don't suppose any more hams understand complex reflection coefficient than understand Smith charts, though. The Smith chart, to me, remains a very valuable _visualization_ tool. It matters not how the points on it were calculated or measured. I think it will always be the case that information properly presented graphically will generally be easier to understand and easier to draw conclusions from than information presented in text in tabular form. Some graphical tools, such as the Smith chart, are worth getting to know, even if you don't use the chart itself to do calculations, deferring instead to other calculators for that part. Pictures, often, are worth much more than 1000 words. Cheers, Tom |
ATU: Correct way to specify impedance range
K7ITM wrote:
The Smith chart, to me, remains a very valuable _visualization_ tool. Here's a recent posting of mine from eHam.net: someone wrote: There are very few people out there that use the Smith Chart. I'm not suggesting that they actually use a Smith Chart - just that they learn how to use one and keep the Smith Chart in their heads as a conceptual tool. With a conceptual image of a Smith Chart in their heads, they not only know what the input and output impedances are but also the path the impedance took to get from one point to another. Did the SWR spiral cross the 50 ohm circle or the 1/50 mho circle during its transition? If so, matching to 50 ohms is a one component piece of cake. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
ATU: Correct way to specify impedance range
On May 21, 11:43*am, Jeff Liebermann wrote:
On Thu, 21 May 2009 07:28:25 -0700 (PDT), ve2pid wrote: Hi to all, Just got my new ATU. The specs mentionned: Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about 3:1) It sems that this is the standardized (?) way to mention specifications... But, since impedances have both a resistive and reactive compoment, doses it means 6 to 600 Ohms "resistive"? For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms.. Thanks de Pierre Well, a little Googleing found the missing maker and model number. It's obviously made by LDG but which product? http://www.ldgelectronics.com The spec sheets aren't any more useful. *I'm also rather suspicious because ALL their products, regardless of size or technology, have the same specification. That's because all their tuners have the same component values (L and C) in the same basic tuner configuration (switched L). The various models just have different power ratings (and I suppose the loss is different) and different other features. It's a fairly straightforward process (albeit tedious) to map out all possible places on the smith chart that can be tuned to 50 ohms by their tuners. Somewhere around I have some plots I did with matlab for just that. Basically, you can get close by knowing the minimum and maximum L and C available. The step size (which is fairly even across the range... they have L and C in the 1,2,4,8 sequence) determines how close you can get to 50 ohms from some arbitrary load Z (assuming it's in range). The power limitations on a tuner are sort of complex (which is why you don't see a lot of detail). There's the current through the L and C, and the voltage on the C. There's no simple relationship between, say, vswr and component voltage/current, since it depends on the particular match configuration. What you can assume is that the potential rise is proportional to the Q of the antenna and tuner together. Since antenna Q is usually fairly low compared to tuner components, you could probably get close by taking the ratio of the antenna's reactive component to the resistive component. (short verticals, notorious for high voltages in a tuning network, have high reactance and small resistance..) |
Correct way to specify impedance range
Impedance is the product of inductive and capacitive reactance in a AC circuit Resistance is the load in a DC circuit. I think impedance has a different affect at different frequencies..... Please correct me if I got all my theory wrong. Rollie |
Correct way to specify impedance range
On May 23, 5:32�pm, "Rollie" wrote:
Impedance is the product of inductive and capacitive reactance in a AC circuit Resistance is the load in a DC circuit. I think impedance has a different affect at different frequencies..... Please correct me if I got all my theory wrong. Rollie Simply put, impedance is frequency dependent, resistance is not. Thats why it is hard to specify a resistance or impedance range for a tuner. Our antennas are frequency dependent because a 50 ohm match is required no matter what frequency we transmit. Gary N4AST |
ATU: Correct way to specify impedance range
On May 21, 10:28*am, ve2pid wrote:
Hi to all, Just got my new ATU. The specs mentionned: Tunes 6 to 600 ohms (about 10:1 SWR range). 16 to 150 on 6M (about 3:1) It sems that this is the standardized (?) way to mention specifications... But, since impedances have both a resistive and reactive compoment, doses it means 6 to 600 Ohms "resistive"? For example , if Z= 500-J800 ohm, is it 'tunable'? I have a doubt because the impedance could also mean sqrt(500^2+800^2)=943,4 Ohms.. Thanks de Pierre FYI finally got the answer from LDG: ---- It's polar coordinates (as opposed to rectangular). For example: 200 -j300 in rectangular would have a magnitude of 360 in polar. I think we were the first company to ever publish tuning specs for autotuners and I happen to choose polar that day, so that's what everyone else uses now for autotuners. It's just an approximate number, but it gives you a rough idea of what to expect. If you find that your long wire (for example) has an impedance of 2500 ohms (either measured or simulated), you can be pretty sure that our tuner is not going to tune it. ---- So, I deduct 600 Ohms could mean any impedance A+JB where sqrt (A^2+b^2)=600. ;-) ........ |
ATU: Correct way to specify impedance range
In article
, ve2pid wrote: I think we were the first company to ever publish tuning specs for autotuners and I happen to choose polar that day, so that's what everyone else uses now for autotuners. Unless you published your specs over 20 years ago, Motorola was the first one to publish Tuning Range Specs, for their Second Generation Autotuner, back when Bill Shielb was Chief Engineer for the MF/HF SSB Engineering Group...... Most of the Modern Day Binary Lumped Constant AutoTuners are based on his work at Motorola, which he brought out west, when he came to Northern Radio Co., and then finally to Berlonix Corp. The SEA-1600 by SEA, (Stephens Engineering Assoc.) was a reverse engineered AutoTuner based on Bills work, done my Mark Johnson and Bill Forgey at SEA, but with a much improved Microprocessor Control algorithm, Phase and Power Sensors, and spawned a long Series of SEA16xx Autotuners, of which the SEA1612B was the most recognized, and the SGC Tuners were copies. |
ATU: Correct way to specify impedance range
K7ITM wrote:
It would be good if they plotted the range on something like a Smith chart. It should be done for different frequencies; it's rare indeed for a tuner to be able to match the same range of impedances over its frequency range. Some tuner topologies even have "holes" in their coverage. Exactly ! You will find here an example: http://www.darc.de/distrikte/c/09/Claude/Z-Match.pdf 73 de Claude |
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