Nano VNA 10M Dipole Sweep

David Gerhart · 2025-01-17T10:00:47-08:00

Fresh out of box. A sweep of my DIY 10M antenna... S1 - connected to 50' Rg58 via BNC connectors to my 10M dipole. The lowest piece of which is about 12' off of the ground. I set markers a L, M and H

Nano VNA 10M Dipole Sweep

David KK7WXV All Messages By This Member #39064 Fresh out of box. A sweep of my DIY 10M antenna... S1 - connected to 50' Rg58 via BNC connectors to my 10M dipole. The lowest piece of which is about 12' off of the ground. I set markers a L, M and H points of the band. S2 port had nothing connected. The VNA was calibrated just prior to the sweep. An anchored via USB to my Windows tablet. Now I'm digging into how to read the Smith Chard and return / impedance info... Comments please!! Do I need to update VNA firmware or make other changes. Software on the tablet? What's next folks? 10M Sweep - LMH markers.PNG
W0LEV All Messages By This Member #39065 You don't even have to consult the Smith Chart. The application has done that for you. To the left of the Smith Chart, the application has given you the following information for the three markers you placed: [image: image.png] Marker 1: Impedance = 40.1 + j 15.4 ohms Marker 2: Impedance = 49.4 + j 40.6 ohms Marker 3: Impedance = 99.2 + j 58.2 ohms There's lot's more information, but everything is inductive - plus sign to the complex portion of the impedance. This would indicate the wires are a bit too long. Although the match at the lowest frequency, Marker 1 at 28.300 MHz, is not bad at all and nothing to be concerned about. Still at Marker 2 at 29.000 MHz, not bad. However, the last marker at 29.700 MHz is beginning to show some compromises. The SWR is also given at the top of the second column for each marker frequency. Dave - W?LEV On Wed, Jan 15, 2025 at 12:00?AM David Gerhart via groups.io <DAVID= [email protected]> wrote: Fresh out of box. A sweep of my DIY 10M antenna... S1 - connected to 50' Rg58 via BNC connectors to my 10M dipole. The lowest piece of which is about 12' off of the ground. I set markers a L, M and H points of the band. S2 port had nothing connected. The VNA was calibrated just prior to the sweep. An anchored via USB to my Windows tablet. Now I'm digging into how to read the Smith Chard and return / impedance info... Comments please!! Do I need to update VNA firmware or make other changes. Software on the tablet? What's next folks? -- Dave - W?LEV -- Dave - W?LEV image.png
Tom KG3V All Messages By This Member #39066 Looks good. I also just got a nano and have not tried it yet. As a Ham, I am used to looking at VSWR sweep for antennas. It looks like you have not yet found the whole SWR dip, as the lowest SWR is at the lowest point on the sweep. If it were me, I would use that low frequency as the new Center frequency and do another sweep. Maybe want to display the SWR format, as that is probably the easiest to interpret. Enjoy the new toy, Tom toggle quoted message Show quoted text On 1/14/25 18:55, David Gerhart wrote: Fresh out of box. A sweep of my DIY 10M antenna... S1 - connected to 50' Rg58 via BNC connectors to my 10M dipole. The lowest piece of which is about 12' off of the ground. I set markers a L, M and H points of the band. S2 port had nothing connected. The VNA was calibrated just prior to the sweep. An anchored via USB to my Windows tablet. Now I'm digging into how to read the Smith Chard and return / impedance info... Comments please!! Do I need to update VNA firmware or make other changes. Software on the tablet? What's next folks?
Siegfried Jackstien All Messages By This Member #39067 did you calibrate with the coax used? (means short, open, load at the cable end) looks like your antenna is a bit on the long side no need to cut the ends .. just fold them over (cause if you hang it higher you may need that length back) .. and secure with cable tie i prefer nanovna app on the pc side ... about the fw ... what fw is on your device?? what device do you have?? dg9bfc sigi Am 15.01.2025 um 00:55 schrieb David Gerhart: toggle quoted message Show quoted text Fresh out of box. A sweep of my DIY 10M antenna... S1 - connected to 50' Rg58 via BNC connectors to my 10M dipole. The lowest piece of which is about 12' off of the ground. I set markers a L, M and H points of the band. S2 port had nothing connected. The VNA was calibrated just prior to the sweep. An anchored via USB to my Windows tablet. Now I'm digging into how to read the Smith Chard and return / impedance info... Comments please!! Do I need to update VNA firmware or make other changes. Software on the tablet? What's next folks?
David KK7WXV All Messages By This Member #39068 Thanks for asking! "did you calibrate with the coax used? (means short, open, load at the cable end) I calibrated by attaching the calibrants directly to the Nano VNA H. "looks like your antenna is a bit on the long side..." Concur! i prefer nanovna app on the pc side ... about the fw ... what fw is on your device?? what device do you have?? I'Il search for that app. The device is a Nano VNA - H2.
Dan Pate - AI5OL All Messages By This Member #39069 You should calibrate as close to the reference plane you are wanting to test as possible. For an antenna that would typically be at the feed point. 73 de Dan AI5OL toggle quoted message Show quoted text On 1/14/2025 10:08 PM, David Gerhart wrote: Thanks for asking! "did you calibrate with the coax used? (means short, open, load at the cable end) I calibrated by attaching the calibrants directly to the Nano VNA H. "looks like your antenna is a bit on the long side..." Concur! i prefer nanovna app on the pc side ... about the fw ... what fw is on your device?? what device do you have?? I'Il search for that app. The device is a Nano VNA - H2. -- 73 de Dan AI5OL -- This email has been checked for viruses by Avast antivirus software. www.avast.com
Fran?ois All Messages By This Member #39070 Hello Do not lose sight of the fact that the nanoVNA is a kind of measuring bridge that will indicate to you, among other things but above all, the impedance at the point where you did the OSL calibration (open closed load). If you did this measurement and calibration at the end of the cable connected to your station, it is the impedance of your antenna, brought back by the cable that you see. Do a test by adding a length of cable, without changing the calibration, and you will see that this length of cable rotates the impedance figure on the Smith diagram. However, not all the points rotate by the same angle because the rotation is a function of the ratio between the length of the cable and the wavelength. If your antenna is easily grounded, you can do your calibration at the connection point of your cable with the antenna, while leaving your NaoVNA at the end of the cable, station side. By replacing the antenna in position, you will measure the real impedance of your antenna. It will be up to you to decide whether or not to integrate the chock balun (if you use one) into the antenna. In any case, your measurement will take into account the parasitic radiation of your transmission line. Several participants say that your antenna is too long because you are measuring an inductive impedance. As explained above, the line length rotates the impedance on the Smith. It may be that in fact your antenna is too short (capacitive) and that the rotation would make it appear too long (inductive). What is certain is that it is not perfectly adapted. If it were, on the Smith, it would be a point (very theoretical) in the center of the Smith. The cable would rotate this point but since it is in the center, it would not move. -- F1AMM Fran?ois toggle quoted message Show quoted text -----Message d'origine----- De la part de David Gerhart Envoyé : mercredi 15 janvier 2025 00:55
David KK7WXV All Messages By This Member #39071 Francois, I calibrated at the S1 port directly. Then I connected S1 to the feed line and subsequently the antenna. The plane I measured would be where the feed line attaches to the radio.
Fran?ois All Messages By This Member #39072 I calibrated at the S1 port directly. Then I connected S1 to the feed line and subsequently the antenna. The plane I measured would be where the feed line attaches to the radio. ** Yes, I understood what you did. It is not a mistake. You measure the impedance of your antenna, brought back by your cable. It is the impedance that your TX sees in transmission. Where it is a mistake is the deduction of saying that the antenna is too long. You could, through software like SimNEC, find (see) the calculated impedance of the other end of the cable (antenna side). But: - You have to know how to use SimNEC which is not obvious - Know what you are doing - Assume that the cable is the one you are using - Know the exact length of the cable Add a length of cable (Tx side) and you will see that the impedance brought back changes -- F1AMM Fran?ois -----Message d'origine----- De la part de David Gerhart Envoyé : mercredi 15 janvier 2025 07:12
Siegfried Jackstien All Messages By This Member #39073 at best calibrate at the cable end .... then you see the impedance of the antenna alone ...? not with cable (that may rotate you results in Smith) dg9bfc Sigi Am 15.01.2025 07:23 schrieb "Fran?ois via groups.io" <18471@...>: toggle quoted message Show quoted text I calibrated at the S1 port directly.? Then I connected S1 to the feed line and subsequently the antenna. The plane I measured would be where the feed line attaches to the radio. ** Yes, I understood what you did. It is not a mistake. You measure the impedance of your antenna, brought back by your cable. It is the impedance that your TX sees in transmission. Where it is a mistake is the deduction of saying that the antenna is too long. You could, through software like SimNEC, find (see) the calculated impedance of the other end of the cable (antenna side). But: - You have to know how to use SimNEC which is not obvious - Know what you are doing - Assume that the cable is the one you are using - Know the exact length of the cable Add a length of cable (Tx side) and you will see that the impedance brought back changes -- F1AMM Fran?ois -----Message d'origine----- De la part de David Gerhart Envoyé : mercredi 15 janvier 2025 07:12
Fran?ois All Messages By This Member #39074 Maybe want to display the SWR format, as that is probably the easiest to interpret. ** The easiest to interpret: yes But it is not the most relevant. In SWR you display 2 variables; in Smith you display 3. The SWR does not allow to adjust an antenna because, on the Smith, the minimum SWR corresponds to the point closest to the center of the Smith and not to the resonance of the antenna which is the place where the curve intersects the horizontal axis (rective = 0) -- F1AMM Fran?ois -----Message d'origine----- De la part de Tom KG3V Envoyé : mercredi 15 janvier 2025 01:19
Greg Giglio All Messages By This Member #39075 Hey David, ? ? Good morning. Everything looks pretty good, and I'm sure you've noted the points about calibrating at the antenna feedpoint.? When transmitting at low power, does your radio / SWR meter indicate pretty much in line with your VNA reading? 10m is a fairly wide band, and if your reading is still inductive, you might try something like inserting a 100pf mica / ceramic cap (at least 500V rating) across the elements at the feedpoint to see if that shifts the impedance / SWR curve more to your liking.? Congrats on taking the plunge with a DIY antenna, as well as making the effort to see HOW it works...Use common-sense precautions of course to protect your equipment, but remember that if it works, just have fun with it!?? 73 de KN7GIG toggle quoted message Show quoted text On Wednesday, January 15, 2025 at 06:24:49 AM EST, Siegfried Jackstien via groups.io <siegfried.jackstien@...> wrote: at best calibrate at the cable end .... then you see the impedance of the antenna alone ...? not with cable (that may rotate you results in Smith) dg9bfc Sigi Am 15.01.2025 07:23 schrieb "Fran?ois via groups.io" <18471@...>: I calibrated at the S1 port directly.? Then I connected S1 to the feed line and subsequently the antenna. The plane I measured would be where the feed line attaches to the radio. ** Yes, I understood what you did. It is not a mistake. You measure the impedance of your antenna, brought back by your cable. It is the impedance that your TX sees in transmission. Where it is a mistake is the deduction of saying that the antenna is too long. You could, through software like SimNEC, find (see) the calculated impedance of the other end of the cable (antenna side). But: - You have to know how to use SimNEC which is not obvious - Know what you are doing - Assume that the cable is the one you are using - Know the exact length of the cable Add a length of cable (Tx side) and you will see that the impedance brought back changes -- F1AMM Fran?ois -----Message d'origine----- De la part de David Gerhart Envoyé : mercredi 15 janvier 2025 07:12
Tom KG3V All Messages By This Member #39076 Why not perform an swr sweep and see where the min swr falls? The impedance will change with exact length of feedline but thr swr min. should show you where your antenna is closest to resonance. 73, Tom, KG3V toggle quoted message Show quoted text On January 15, 2025 8:05:36 AM "Greg Giglio" <coffeeguy2@...> wrote: Hey David, Good morning. Everything looks pretty good, and I'm sure you've noted the points about calibrating at the antenna feedpoint. When transmitting at low power, does your radio / SWR meter indicate pretty much in line with your VNA reading? 10m is a fairly wide band, and if your reading is still inductive, you might try something like inserting a 100pf mica / ceramic cap (at least 500V rating) across the elements at the feedpoint to see if that shifts the impedance / SWR curve more to your liking. Congrats on taking the plunge with a DIY antenna, as well as making the effort to see HOW it works...Use common-sense precautions of course to protect your equipment, but remember that if it works, just have fun with it! 73 de KN7GIG On Wednesday, January 15, 2025 at 06:24:49 AM EST, Siegfried Jackstien via groups.io <siegfried.jackstien@...> wrote: at best calibrate at the cable end .... then you see the impedance of the antenna alone ... not with cable (that may rotate you results in Smith) dg9bfc Sigi Am 15.01.2025 07:23 schrieb "Fran?ois via groups.io" <18471@...>: I calibrated at the S1 port directly. Then I connected S1 to the feed line and subsequently the antenna. The plane I measured would be where the feed line attaches to the radio. ** Yes, I understood what you did. It is not a mistake. You measure the impedance of your antenna, brought back by your cable. It is the impedance that your TX sees in transmission. Where it is a mistake is the deduction of saying that the antenna is too long. You could, through software like SimNEC, find (see) the calculated impedance of the other end of the cable (antenna side). But: - You have to know how to use SimNEC which is not obvious - Know what you are doing - Assume that the cable is the one you are using - Know the exact length of the cable Add a length of cable (Tx side) and you will see that the impedance brought back changes -- F1AMM Fran?ois -----Message d'origine----- De la part de David Gerhart Envoyé : mercredi 15 janvier 2025 07:12
Roger Need All Messages By This Member #39084 There is an excellent free program for Windows that really helps to understand how transmission lines work. It is called TLDetails >> Using this program you can select from commonly available transmission lines (RG8, RG58, twinlead etc.), set a load impedance, cable length and frequency and then it calculates the SWR, Return Loss, impedance and plots on a Smith Chart. Many other useful features as well. Here is an example. Capture.PNG
W0LEV All Messages By This Member #39085 SimSmith can do all this and far more..... And.....its freeware: And an excellent tutorial: Dave - W?LEV On Thu, Jan 16, 2025 at 5:32?PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: There is an excellent free program for Windows that really helps to understand how transmission lines work. It is called TLDetails >> Using this program you can select from commonly available transmission lines (RG8, RG58, twinlead etc.), set a load impedance, cable length and frequency and then it calculates the SWR, Return Loss, impedance and plots on a Smith Chart. Many other useful features as well. Here is an example. -- Dave - W?LEV -- Dave - W?LEV
Roger Need All Messages By This Member #39086 On Thu, Jan 16, 2025 at 10:09 AM, W0LEV wrote: SimSmith can do all this and far more..... And.....its freeware: Yes it can do much more and it has a steep learning curve... Roger
W0LEV All Messages By This Member #39087 The best way to conquer the "steep learning curve" is to just dig in..... Dave - W?LEV On Thu, Jan 16, 2025 at 6:17?PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: On Thu, Jan 16, 2025 at 10:09 AM, W0LEV wrote: SimSmith can do all this and far more..... And.....its freeware: Yes it can do much more and it has a steep learning curve... Roger -- Dave - W?LEV -- Dave - W?LEV
William Schrader All Messages By This Member #39088 RE: "digging in" Old proverb: "When you're up to your ass in alligators it's hard to remember that your job was to drain the swamp!" Bill K2TNO On Thu, Jan 16, 2025 at 6:19?PM W0LEV via groups.io <davearea51a= [email protected]> wrote: The best way to conquer the "steep learning curve" is to just dig in..... Dave - W?LEV On Thu, Jan 16, 2025 at 6:17?PM Roger Need via groups.io <sailtamarack= [email protected]> wrote: On Thu, Jan 16, 2025 at 10:09 AM, W0LEV wrote: SimSmith can do all this and far more..... And.....its freeware: Yes it can do much more and it has a steep learning curve... Roger -- Dave - W?LEV -- Dave - W?LEV
?lvaro Felipe Hernández All Messages By This Member #39089 Whenever I have made measurements to antennas I have had very different results -even calibrating the antenna feed coaxial cable- than placing my VNA-F with a 10 cm. patch cord directly to the antenna feed. Obviously I have had to remove the antenna feed cable and calibrate the VNA with the cable stretched on the ground. If you want a precise and real measurement you should connect the NANO-VNA as close as possible to the antenna feed point. -- ALVARO, EA8ARX
Fran?ois All Messages By This Member #39090 If you want a precise and real measurement you should connect the NANO-VNA as close as possible to the antenna feed point. I have a -F and I have never encountered this problem with either a 10 m coaxial or a 40 m coaxial (3-30 MHz). I make my measurements from the station, the NanoVNA being connected to my PC. The measurements I make, by calibrating at the connection to the antenna are a priori good since this is where I insert my LC adapters. These adapters are calculated on the basis of the s1P files; I measure the components. Then I refine the settings by mounting the adapter upside down in order to find the impedance measured in the s1p. And it works. This is also the only way to integrate the coaxial sheath into the measuring device. -- F1AMM Fran?ois -----Message d'origine----- De la part de ?lvaro Felipe Hernández Envoyé : vendredi 17 janvier 2025 15:40

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Nano VNA 10M Dipole Sweep