SDR-Kits Female SMA Calibration Kit query
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Hi,
I've purchased a SDR-Kits Female Calibration Kit of Rosenberger parts, it's intended for DG8SAQ VNWA, but I don't have that, I intend to use it with N2PK VNA, and R&S FPC1500 VNA. I had a question, which I'll eventually e-mail SDR-Kits with, but I thought it would be worth asking on the N2PK mailer first, since others may have done the same thing as me and obtained this. The question I have, is (perhaps a really basic one! in which case I apologize), in the screenshot in their datasheet, they show an offset delay, and a derived electrical length. A snippet from the datasheet is shown below; you can see the two-way delay of 84.70ps, and a one-way electrical length of 8.87mm. Using some simple math, I had previously believed that the offset delay can be converted to electrical length by multiplying by 0.3, i.e. 84.70ps would become 25.41mm, and half of that (since they are using two-way delay for some reason) would be 12.705mm. [cid:fd356d6e-2451-4e33-b967-7186a635a220] Link to the PDF full datasheet: I installed the VNWA software and entered the 84.7ps value myself, and it calculated 8.887 mm mechanical? length, so that settles that the datasheet has an older incorrect screenshot, which is minor but I'll raise it with them since it is confusing to readers. However, more importantly, I'm curious how the VNWA software arrived at that value anyway, because a conversion of 8.887 mm mechanical to electrical would be 1.5 times 8.887 which equals 13.33mm , but it's still quite different from my computation of 12.705mm. [cid:f102a3a1-f2fd-44a2-a45d-f69c90ba23ba] My question is, how did they come up with the electrical length? Am I calculating it wrong, or is the VNWA software calculating it wrong? It's important to me, because on my FPC1500 VNA, the only values I can enter are lengths, so I need to know if I should be typing 12.705, or 13.33, or something else! : ) [cid:8801385d-6178-4b9f-8cc4-f688d723556c] Personally, I believe it should be 12.705, because when I calibrate like that, I believe I'm getting decent measurements. But I'd like to know if this is just luck, or if I am actually using the correct formula. Any help would be gratefully appreciated. Many thanks, Shabaz. |
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Hi Shabaz
I am the author of the datasheet you link to, and I can give the answers to all your questions. I insert my responses below. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 16:27 Til: [email protected] Emne: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi, I've purchased a SDR-Kits Female Calibration Kit of Rosenberger parts, it's intended for DG8SAQ VNWA, but I don't have that, I intend to use it with N2PK VNA, and R&S FPC1500 VNA. I had a question, which I'll eventually e-mail SDR-Kits with, but I thought it would be worth asking on the N2PK mailer first, since others may have done the same thing as me and obtained this.You can actually run the N2PK VNA by the VNWA software as it has an interface for that purpose. Read about it in the embedded helpfile. Regarding the R&S FPC1500 VNA you probably need to derive L C coefficients and I have written an article how to do so. You need anyway to select the female calibration kit of Rosenberger parts in the VNWA software to utilize my document attached.<<<< The question I have, is (perhaps a really basic one! in which case I apologize), in the screenshot in their datasheet, they show an offset delay, and a derived electrical length. A snippet from the datasheet is shown below; you can see the two-way delay of 84.70ps, and a one-way electrical length of 8.87mm.Good point <<<< Using some simple math, I had previously believed that the offset delay can be converted to electrical length by multiplying by 0.3, i.e. 84.70ps would become 25.41mm, and half of that (since they are using two-way delay for some reason) would be 12.705mm.It is not an offset delay but a negative two way delay, which it the travel delay forth and back for a reflection, and the way the VNWA software is designed. For the commercial VNA's such as HP, R&S, Anritsu and more, is used a positive offset delay being 50% of the numeric two way delay, as you rightly mention below.<<<< [cid:fd356d6e-2451-4e33-b967-7186a635a220]Your simple math is almost correct but only for an airline, the open standard is the FF adaptor and it contains a Teflon insert with a velocity factor of 0.695 so your simple calculation is now 84.7ps x 0.3 = 17.66 /2 = 8.883mm but still with an error explained in details below <<<< Link to the PDF full datasheet: I installed the VNWA software and entered the 84.7ps value myself, and it calculated 8.887 mm mechanical? length, so that settles that the datasheet has an older incorrect screenshot, which is minor but I'll raise it with them since it is confusing to readers. However, more importantly, I'm curious how the VNWA software arrived at that value anyway, because a conversion of 8.887 mm mechanical to electrical would be 1.5 times 8.887 which equals 13.33mm , but it's still quite different from my computation of 12.705mm [cid:f102a3a1-f2fd-44a2-a45d-f69c90ba23ba]Correct the document is an older one showing physical length of 8.87mm but the present VNWA software show 8.887mm because the VNWA software has since been modified to reflect the true speed of light and not the assumed factor 0.3 you mentioned in the beginning of you mail. Se the second attached report about true speed of light and more. Please also noted that the VNWA has under the calibration kit a folder called "Special Settings" which contain the velocity factor entered default as 0.7. Tom Baier has entered 0.7 for the Teflon inserts and I have mentioned 0.695 and what is correct is a matter of discussion both are found in the literature. <<<< My question is, how did they come up with the electrical length? Am I calculating it wrong, or is the VNWA software calculating it wrong? It's important to me, because on my FPC1500 VNA, the only values I can enter are lengths, so I need to know if I should be typing 12.705, or 13.33, or something else! : ) [cid:8801385d-6178-4b9f-8cc4-f688d723556c] Personally, I believe it should be 12.705, because when I calibrate like that, I believe I'm getting decent measurements. But I'd like to know if this is just luck, or if I am actually using the correct formula. I hope this has clarified you concerns<<<Watch out for the offset length for your FPC1500 VNA if it is positive or negative. The VNWA calculate a negative delay to a negative length. A negative delay in ps for the VNWA lead to a positive offset delay in ps. Any help would be gratefully appreciated. Many thanks, Shabaz. |
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Hi Shabaz
UPS, here are the documents Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 16:27 Til: [email protected] Emne: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi, I've purchased a SDR-Kits Female Calibration Kit of Rosenberger parts, it's intended for DG8SAQ VNWA, but I don't have that, I intend to use it with N2PK VNA, and R&S FPC1500 VNA. I had a question, which I'll eventually e-mail SDR-Kits with, but I thought it would be worth asking on the N2PK mailer first, since others may have done the same thing as me and obtained this. The question I have, is (perhaps a really basic one! in which case I apologize), in the screenshot in their datasheet, they show an offset delay, and a derived electrical length. A snippet from the datasheet is shown below; you can see the two-way delay of 84.70ps, and a one-way electrical length of 8.87mm. Using some simple math, I had previously believed that the offset delay can be converted to electrical length by multiplying by 0.3, i.e. 84.70ps would become 25.41mm, and half of that (since they are using two-way delay for some reason) would be 12.705mm. [cid:fd356d6e-2451-4e33-b967-7186a635a220] Link to the PDF full datasheet: I installed the VNWA software and entered the 84.7ps value myself, and it calculated 8.887 mm mechanical? length, so that settles that the datasheet has an older incorrect screenshot, which is minor but I'll raise it with them since it is confusing to readers. However, more importantly, I'm curious how the VNWA software arrived at that value anyway, because a conversion of 8.887 mm mechanical to electrical would be 1.5 times 8.887 which equals 13.33mm , but it's still quite different from my computation of 12.705mm. [cid:f102a3a1-f2fd-44a2-a45d-f69c90ba23ba] My question is, how did they come up with the electrical length? Am I calculating it wrong, or is the VNWA software calculating it wrong? It's important to me, because on my FPC1500 VNA, the only values I can enter are lengths, so I need to know if I should be typing 12.705, or 13.33, or something else! : ) [cid:8801385d-6178-4b9f-8cc4-f688d723556c] Personally, I believe it should be 12.705, because when I calibrate like that, I believe I'm getting decent measurements. But I'd like to know if this is just luck, or if I am actually using the correct formula. Any help would be gratefully appreciated. Many thanks, Shabaz. |
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Hi Shabaz
See below for reply. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 22:25 Til: [email protected] Emne: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Kurt, Thanks for this. I've looked through the docs, and had the following questions: 1. In "Basic Transmission line" doc, I see the text: Similar techniques are used for the female short which is simpler as not having a fringe component to take care of. The nominel Z0 calculated based on the physical dimension measured with the caliper and the delay in ps calculated based on the depth in mm divided by 0.3. and in SOT259 Calibration Standards (which is referenced), there is the text "velocity factor VF which e.g. for PTFE is 0.695. Such an anticipation leads to a delay in ps by the length in mm divided by 0.3 divided and by VF. This anticipation is only valid for a Z0 of 50 ohm." Those snippets appear to confirm that given an offset delay, it can be converted into an electrical length by multiplying by 0.3. Is this correct? Or have I misunderstood? If correct, can I simply take the Female SMA Kit datasheet value of 26.91 ps for the short, and multiply by 0.3, to get an electrical length of 8.073mm? And can I take the datasheet value of 42.35ps for the short at VHF, and again multiply by 0.3 to get an electrical length of 12.705mm? My VNA requires one-way electrical lengths, not delay values. 2.Yes that is correct and the mechanical length is then the electrical length multiplied by VF because the wave is travelling slower in the Teflon insert. Check this by comparing to the VNWA which is calculating mechanical length.<<<< How does the answer in (1) square up with the screenshots in the datasheet? The datasheet screenshots show one-way electrical length values of 5.647 and 8.87mm respectively for the short and the open. As iI mentioned the calculation in the screenshot for the datasheet is based on the inaccurate assumption of speed of light300.0000 meters/second, and the present version of VNWA software is using the accurate value ???.????meters/second . This change of the VNWA software done after the datasheet was created.<<<< 3. How does the answer in (1) square up with the values that the current VNWA software release indicates when the user plugs in the delay values? I see the VNWA software reports one-way mechanical lengths of -5.647 and 8.887mm respectively when the two-way delay values are entered. How does the VNWA software report mechanical length when there is nowhere to enter a velocity factor? It doesn't appear to be assuming a value of 0.695. No it is based on VF 0.7 and entered under "special Settings as I wrote<<< Prodessional calibration kit does not have Teflon as insert but are with air as isolation and the center conductor only supported by thin discs. They are measured and characterized both due to mechanical dimensions but also by frequency dependent parameter mostly by L0 to L3 and C0 to C3 where L0 and C0 are not frequency dependent <<<<Alternative in air with VF=1 the exact one way travel is 3.335605mm/ps and by VF=0.7 4.765151mm/ps and for VF=0.695 4.799433mm/ps Again, apologies if these are very basic questions, I just want to get it as clear in my head as I can (given that I'm only as knowledgeable in math as the average person - I've a Masters degree in engineering, but my expertise lies in unrelated fields). Many thanks, Shabaz. ________________________________ From: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> on behalf of Kurt Poulsen < <mailto:kurt@...> kurt@...> Sent: 05 March 2024 19:38 To: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> Subject: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Shabaz UPS, here are the documents Kind regards Kurt -----Oprindelig meddelelse----- Fra: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 16:27 Til: <mailto:[email protected]> [email protected] Emne: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi, I've purchased a SDR-Kits Female Calibration Kit of Rosenberger parts, it's intended for DG8SAQ VNWA, but I don't have that, I intend to use it with N2PK VNA, and R&S FPC1500 VNA. I had a question, which I'll eventually e-mail SDR-Kits with, but I thought it would be worth asking on the N2PK mailer first, since others may have done the same thing as me and obtained this. The question I have, is (perhaps a really basic one! in which case I apologize), in the screenshot in their datasheet, they show an offset delay, and a derived electrical length. A snippet from the datasheet is shown below; you can see the two-way delay of 84.70ps, and a one-way electrical length of 8.87mm. Using some simple math, I had previously believed that the offset delay can be converted to electrical length by multiplying by 0.3, i.e. 84.70ps would become 25.41mm, and half of that (since they are using two-way delay for some reason) would be 12.705mm. [cid:fd356d6e-2451-4e33-b967-7186a635a220] Link to the PDF full datasheet: <> <> I installed the VNWA software and entered the 84.7ps value myself, and it calculated 8.887 mm mechanical? length, so that settles that the datasheet has an older incorrect screenshot, which is minor but I'll raise it with them since it is confusing to readers. However, more importantly, I'm curious how the VNWA software arrived at that value anyway, because a conversion of 8.887 mm mechanical to electrical would be 1.5 times 8.887 which equals 13.33mm , but it's still quite different from my computation of 12.705mm. [cid:f102a3a1-f2fd-44a2-a45d-f69c90ba23ba] My question is, how did they come up with the electrical length? Am I calculating it wrong, or is the VNWA software calculating it wrong? It's important to me, because on my FPC1500 VNA, the only values I can enter are lengths, so I need to know if I should be typing 12.705, or 13.33, or something else! : ) [cid:8801385d-6178-4b9f-8cc4-f688d723556c] Personally, I believe it should be 12.705, because when I calibrate like that, I believe I'm getting decent measurements. But I'd like to know if this is just luck, or if I am actually using the correct formula. Any help would be gratefully appreciated. Many thanks, Shabaz. |
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Hi Kurt,
Thank you, that's all clear and makes sense, perfect! For newcomers, they will find it confusing that the screenshot in the datasheet mentions "electrical length" yet gives values which are quite different, so (just a personal opinion) it may be worth on the next revision to replace the screenshots. Maybe only nit-picking people that may spot that though! : ) I spotted it because I'm a non-expert and tried to see where the numbers came from. [cid:7b7bae99-bc97-45ab-8231-043002086333] Another very minor point, there's a typo (I think), where the text "male open" should be "female open". I may have misunderstood this bit. [cid:0b11da54-0440-44d3-a90a-6719f1b041b5] Other than that, the datasheet was very good, and very clear annotated photos! Thanks again for the documents too - they will come in extremely useful, there's a lot of valuable information there. Many thanks, Shabaz. ________________________________ From: [email protected] <[email protected]> on behalf of Kurt Poulsen <kurt@...> Sent: 05 March 2024 22:53 To: [email protected] <[email protected]> Subject: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Shabaz See below for reply. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 22:25 Til: [email protected] Emne: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Kurt, Thanks for this. I've looked through the docs, and had the following questions: 1. In "Basic Transmission line" doc, I see the text: Similar techniques are used for the female short which is simpler as not having a fringe component to take care of. The nominel Z0 calculated based on the physical dimension measured with the caliper and the delay in ps calculated based on the depth in mm divided by 0.3. and in SOT259 Calibration Standards (which is referenced), there is the text "velocity factor VF which e.g. for PTFE is 0.695. Such an anticipation leads to a delay in ps by the length in mm divided by 0.3 divided and by VF. This anticipation is only valid for a Z0 of 50 ohm." Those snippets appear to confirm that given an offset delay, it can be converted into an electrical length by multiplying by 0.3. Is this correct? Or have I misunderstood? If correct, can I simply take the Female SMA Kit datasheet value of 26.91 ps for the short, and multiply by 0.3, to get an electrical length of 8.073mm? And can I take the datasheet value of 42.35ps for the short at VHF, and again multiply by 0.3 to get an electrical length of 12.705mm? My VNA requires one-way electrical lengths, not delay values. 2.Yes that is correct and the mechanical length is then the electrical length multiplied by VF because the wave is travelling slower in the Teflon insert. Check this by comparing to the VNWA which is calculating mechanical length.<<<< How does the answer in (1) square up with the screenshots in the datasheet? The datasheet screenshots show one-way electrical length values of 5.647 and 8.87mm respectively for the short and the open. As iI mentioned the calculation in the screenshot for the datasheet is based on the inaccurate assumption of speed of light300.0000 meters/second, and the present version of VNWA software is using the accurate value ???.????meters/second . This change of the VNWA software done after the datasheet was created.<<<< 3. How does the answer in (1) square up with the values that the current VNWA software release indicates when the user plugs in the delay values? I see the VNWA software reports one-way mechanical lengths of -5.647 and 8.887mm respectively when the two-way delay values are entered. How does the VNWA software report mechanical length when there is nowhere to enter a velocity factor? It doesn't appear to be assuming a value of 0.695. No it is based on VF 0.7 and entered under "special Settings as I wrote<<< Prodessional calibration kit does not have Teflon as insert but are with air as isolation and the center conductor only supported by thin discs. They are measured and characterized both due to mechanical dimensions but also by frequency dependent parameter mostly by L0 to L3 and C0 to C3 where L0 and C0 are not frequency dependent <<<<Alternative in air with VF=1 the exact one way travel is 3.335605mm/ps and by VF=0.7 4.765151mm/ps and for VF=0.695 4.799433mm/ps Again, apologies if these are very basic questions, I just want to get it as clear in my head as I can (given that I'm only as knowledgeable in math as the average person - I've a Masters degree in engineering, but my expertise lies in unrelated fields). Many thanks, Shabaz. ________________________________ From: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> on behalf of Kurt Poulsen < <mailto:kurt@...> kurt@...> Sent: 05 March 2024 19:38 To: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> Subject: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Shabaz UPS, here are the documents Kind regards Kurt -----Oprindelig meddelelse----- Fra: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 16:27 Til: <mailto:[email protected]> [email protected] Emne: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi, I've purchased a SDR-Kits Female Calibration Kit of Rosenberger parts, it's intended for DG8SAQ VNWA, but I don't have that, I intend to use it with N2PK VNA, and R&S FPC1500 VNA. I had a question, which I'll eventually e-mail SDR-Kits with, but I thought it would be worth asking on the N2PK mailer first, since others may have done the same thing as me and obtained this. The question I have, is (perhaps a really basic one! in which case I apologize), in the screenshot in their datasheet, they show an offset delay, and a derived electrical length. A snippet from the datasheet is shown below; you can see the two-way delay of 84.70ps, and a one-way electrical length of 8.87mm. Using some simple math, I had previously believed that the offset delay can be converted to electrical length by multiplying by 0.3, i.e. 84.70ps would become 25.41mm, and half of that (since they are using two-way delay for some reason) would be 12.705mm. [cid:fd356d6e-2451-4e33-b967-7186a635a220] Link to the PDF full datasheet: <<>> <><> I installed the VNWA software and entered the 84.7ps value myself, and it calculated 8.887 mm mechanical? length, so that settles that the datasheet has an older incorrect screenshot, which is minor but I'll raise it with them since it is confusing to readers. However, more importantly, I'm curious how the VNWA software arrived at that value anyway, because a conversion of 8.887 mm mechanical to electrical would be 1.5 times 8.887 which equals 13.33mm , but it's still quite different from my computation of 12.705mm. [cid:f102a3a1-f2fd-44a2-a45d-f69c90ba23ba] My question is, how did they come up with the electrical length? Am I calculating it wrong, or is the VNWA software calculating it wrong? It's important to me, because on my FPC1500 VNA, the only values I can enter are lengths, so I need to know if I should be typing 12.705, or 13.33, or something else! : ) [cid:8801385d-6178-4b9f-8cc4-f688d723556c] Personally, I believe it should be 12.705, because when I calibrate like that, I believe I'm getting decent measurements. But I'd like to know if this is just luck, or if I am actually using the correct formula. Any help would be gratefully appreciated. Many thanks, Shabaz. |
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Hi Shabaz
Well spotted as the datasheet mention "electrical Length" and the present VNWA software described it correctly as "mechanical length" It is probably time for an update of the specification sheet where the correction for the correct value related to the true speed of light is changed as well. There is no error regarding the 1.35ps for male open. A female open mating part for a male calibration kit is a female adaptor. Just think of the TX output on the VNWA or any other VNWA being a female SMA, then a male calibration kit adaptor is nothing connected or just an short empty adaptor with no center pin, It is the fringe capacitance from the female TX center conductor which is constituting the male open. Whether you mount an end cap or nothing you will se no different except going into the many GHz region. If you study the SDR-KITS male kit of Rosenberger parts there is provided such an male endcap which I never use. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 6. marts 2024 00:10 Til: [email protected] Emne: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Kurt, Thank you, that's all clear and makes sense, perfect! For newcomers, they will find it confusing that the screenshot in the datasheet mentions "electrical length" yet gives values which are quite different, so (just a personal opinion) it may be worth on the next revision to replace the screenshots. Maybe only nit-picking people that may spot that though! : ) I spotted it because I'm a non-expert and tried to see where the numbers came from. [cid:7b7bae99-bc97-45ab-8231-043002086333] Another very minor point, there's a typo (I think), where the text "male open" should be "female open". I may have misunderstood this bit. [cid:0b11da54-0440-44d3-a90a-6719f1b041b5] Other than that, the datasheet was very good, and very clear annotated photos! Thanks again for the documents too - they will come in extremely useful, there's a lot of valuable information there. Many thanks, Shabaz. ________________________________ From: [email protected] <[email protected]> on behalf of Kurt Poulsen <kurt@...> Sent: 05 March 2024 22:53 To: [email protected] <[email protected]> Subject: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Shabaz See below for reply. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 22:25 Til: [email protected] Emne: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Kurt, Thanks for this. I've looked through the docs, and had the following questions: 1. In "Basic Transmission line" doc, I see the text: Similar techniques are used for the female short which is simpler as not having a fringe component to take care of. The nominel Z0 calculated based on the physical dimension measured with the caliper and the delay in ps calculated based on the depth in mm divided by 0.3. and in SOT259 Calibration Standards (which is referenced), there is the text "velocity factor VF which e.g. for PTFE is 0.695. Such an anticipation leads to a delay in ps by the length in mm divided by 0.3 divided and by VF. This anticipation is only valid for a Z0 of 50 ohm." Those snippets appear to confirm that given an offset delay, it can be converted into an electrical length by multiplying by 0.3. Is this correct? Or have I misunderstood? If correct, can I simply take the Female SMA Kit datasheet value of 26.91 ps for the short, and multiply by 0.3, to get an electrical length of 8.073mm? And can I take the datasheet value of 42.35ps for the short at VHF, and again multiply by 0.3 to get an electrical length of 12.705mm? My VNA requires one-way electrical lengths, not delay values. 2.Yes that is correct and the mechanical length is then the electrical length multiplied by VF because the wave is travelling slower in the Teflon insert. Check this by comparing to the VNWA which is calculating mechanical length.<<<< How does the answer in (1) square up with the screenshots in the datasheet? The datasheet screenshots show one-way electrical length values of 5.647 and 8.87mm respectively for the short and the open. As iI mentioned the calculation in the screenshot for the datasheet is based on the inaccurate assumption of speed of light300.0000 meters/second, and the present version of VNWA software is using the accurate value ???.????meters/second . This change of the VNWA software done after the datasheet was created.<<<< 3. How does the answer in (1) square up with the values that the current VNWA software release indicates when the user plugs in the delay values? I see the VNWA software reports one-way mechanical lengths of -5.647 and 8.887mm respectively when the two-way delay values are entered. How does the VNWA software report mechanical length when there is nowhere to enter a velocity factor? It doesn't appear to be assuming a value of 0.695. No it is based on VF 0.7 and entered under "special Settings as I wrote<<< Prodessional calibration kit does not have Teflon as insert but are with air as isolation and the center conductor only supported by thin discs. They are measured and characterized both due to mechanical dimensions but also by frequency dependent parameter mostly by L0 to L3 and C0 to C3 where L0 and C0 are not frequency dependent <<<<Alternative in air with VF=1 the exact one way travel is 3.335605mm/ps and by VF=0.7 4.765151mm/ps and for VF=0.695 4.799433mm/ps Again, apologies if these are very basic questions, I just want to get it as clear in my head as I can (given that I'm only as knowledgeable in math as the average person - I've a Masters degree in engineering, but my expertise lies in unrelated fields). Many thanks, Shabaz. ________________________________ From: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> on behalf of Kurt Poulsen < <mailto:kurt@...> kurt@...> Sent: 05 March 2024 19:38 To: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> Subject: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Shabaz UPS, here are the documents Kind regards Kurt -----Oprindelig meddelelse----- Fra: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 16:27 Til: <mailto:[email protected]> [email protected] Emne: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi, I've purchased a SDR-Kits Female Calibration Kit of Rosenberger parts, it's intended for DG8SAQ VNWA, but I don't have that, I intend to use it with N2PK VNA, and R&S FPC1500 VNA. I had a question, which I'll eventually e-mail SDR-Kits with, but I thought it would be worth asking on the N2PK mailer first, since others may have done the same thing as me and obtained this. The question I have, is (perhaps a really basic one! in which case I apologize), in the screenshot in their datasheet, they show an offset delay, and a derived electrical length. A snippet from the datasheet is shown below; you can see the two-way delay of 84.70ps, and a one-way electrical length of 8.87mm. Using some simple math, I had previously believed that the offset delay can be converted to electrical length by multiplying by 0.3, i.e. 84.70ps would become 25.41mm, and half of that (since they are using two-way delay for some reason) would be 12.705mm. [cid:fd356d6e-2451-4e33-b967-7186a635a220] Link to the PDF full datasheet: <<>> <><> I installed the VNWA software and entered the 84.7ps value myself, and it calculated 8.887 mm mechanical? length, so that settles that the datasheet has an older incorrect screenshot, which is minor but I'll raise it with them since it is confusing to readers. However, more importantly, I'm curious how the VNWA software arrived at that value anyway, because a conversion of 8.887 mm mechanical to electrical would be 1.5 times 8.887 which equals 13.33mm , but it's still quite different from my computation of 12.705mm. [cid:f102a3a1-f2fd-44a2-a45d-f69c90ba23ba] My question is, how did they come up with the electrical length? Am I calculating it wrong, or is the VNWA software calculating it wrong? It's important to me, because on my FPC1500 VNA, the only values I can enter are lengths, so I need to know if I should be typing 12.705, or 13.33, or something else! : ) [cid:8801385d-6178-4b9f-8cc4-f688d723556c] Personally, I believe it should be 12.705, because when I calibrate like that, I believe I'm getting decent measurements. But I'd like to know if this is just luck, or if I am actually using the correct formula. Any help would be gratefully appreciated. Many thanks, Shabaz. |
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Hi Shabaz
Excellent document, congratulations, very well written. I think you could add to the line "The VNA indicated in the datasheet happens to use two-way delay values, so the values above need to be multiplied by two to use that VNA" that it is negative delays and the it only applied for refelection settings. The thru delay for transmission shall not be multiplied for VNA's which both can measure reflection and transmission. I wish my full name Kurt Poulsen mentioned instead of just Kurt. Please change the line "The calibration kit datasheet author recommended" to "The calibration kit datasheet author Kurt Poulsen recommended" and please add "which he also is the author off" as you must credit my documents this way. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 6. marts 2024 16:47 Til: [email protected] Emne: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Kurt, Ah, got it. I now understand that male open text. I've written a short guide on how to use the kit with any VNA, it is here: I hope you don't mind, I referenced your name (by first name only, in case you didn't wish your full name present) in the guide. The guide is a little basic, I was trying to write a zero-math (well, nothing much beyond multiplication or division : ) guide to using a VNA for non-experts, since nowadays even engineers who are in non-RF related fields will benefit from VNAs since they are a much lower-cost than before. If you or anyone spot any errors or wish to add any detail, please let me know (either e-mail or comments to the blog) and hopefully it can iterate into being a more refined article. Many thanks, Shabaz. ________________________________ From: [email protected] <[email protected]> on behalf of Kurt Poulsen <kurt@...> Sent: 06 March 2024 10:41 To: [email protected] <[email protected]> Subject: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Shabaz Well spotted as the datasheet mention "electrical Length" and the present VNWA software described it correctly as "mechanical length" It is probably time for an update of the specification sheet where the correction for the correct value related to the true speed of light is changed as well. There is no error regarding the 1.35ps for male open. A female open mating part for a male calibration kit is a female adaptor. Just think of the TX output on the VNWA or any other VNWA being a female SMA, then a male calibration kit adaptor is nothing connected or just an short empty adaptor with no center pin, It is the fringe capacitance from the female TX center conductor which is constituting the male open. Whether you mount an end cap or nothing you will se no different except going into the many GHz region. If you study the SDR-KITS male kit of Rosenberger parts there is provided such an male endcap which I never use. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 6. marts 2024 00:10 Til: [email protected] Emne: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Kurt, Thank you, that's all clear and makes sense, perfect! For newcomers, they will find it confusing that the screenshot in the datasheet mentions "electrical length" yet gives values which are quite different, so (just a personal opinion) it may be worth on the next revision to replace the screenshots. Maybe only nit-picking people that may spot that though! : ) I spotted it because I'm a non-expert and tried to see where the numbers came from. [cid:7b7bae99-bc97-45ab-8231-043002086333] Another very minor point, there's a typo (I think), where the text "male open" should be "female open". I may have misunderstood this bit. [cid:0b11da54-0440-44d3-a90a-6719f1b041b5] Other than that, the datasheet was very good, and very clear annotated photos! Thanks again for the documents too - they will come in extremely useful, there's a lot of valuable information there. Many thanks, Shabaz. ________________________________ From: [email protected] <[email protected]> on behalf of Kurt Poulsen <kurt@...> Sent: 05 March 2024 22:53 To: [email protected] <[email protected]> Subject: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Shabaz See below for reply. Kind regards Kurt -----Oprindelig meddelelse----- Fra: [email protected] <[email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 22:25 Til: [email protected] Emne: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Kurt, Thanks for this. I've looked through the docs, and had the following questions: 1. In "Basic Transmission line" doc, I see the text: Similar techniques are used for the female short which is simpler as not having a fringe component to take care of. The nominel Z0 calculated based on the physical dimension measured with the caliper and the delay in ps calculated based on the depth in mm divided by 0.3. and in SOT259 Calibration Standards (which is referenced), there is the text "velocity factor VF which e.g. for PTFE is 0.695. Such an anticipation leads to a delay in ps by the length in mm divided by 0.3 divided and by VF. This anticipation is only valid for a Z0 of 50 ohm." Those snippets appear to confirm that given an offset delay, it can be converted into an electrical length by multiplying by 0.3. Is this correct? Or have I misunderstood? If correct, can I simply take the Female SMA Kit datasheet value of 26.91 ps for the short, and multiply by 0.3, to get an electrical length of 8.073mm? And can I take the datasheet value of 42.35ps for the short at VHF, and again multiply by 0.3 to get an electrical length of 12.705mm? My VNA requires one-way electrical lengths, not delay values. 2.Yes that is correct and the mechanical length is then the electrical length multiplied by VF because the wave is travelling slower in the Teflon insert. Check this by comparing to the VNWA which is calculating mechanical length.<<<< How does the answer in (1) square up with the screenshots in the datasheet? The datasheet screenshots show one-way electrical length values of 5.647 and 8.87mm respectively for the short and the open. As iI mentioned the calculation in the screenshot for the datasheet is based on the inaccurate assumption of speed of light300.0000 meters/second, and the present version of VNWA software is using the accurate value ???.????meters/second . This change of the VNWA software done after the datasheet was created.<<<< 3. How does the answer in (1) square up with the values that the current VNWA software release indicates when the user plugs in the delay values? I see the VNWA software reports one-way mechanical lengths of -5.647 and 8.887mm respectively when the two-way delay values are entered. How does the VNWA software report mechanical length when there is nowhere to enter a velocity factor? It doesn't appear to be assuming a value of 0.695. No it is based on VF 0.7 and entered under "special Settings as I wrote<<< Prodessional calibration kit does not have Teflon as insert but are with air as isolation and the center conductor only supported by thin discs. They are measured and characterized both due to mechanical dimensions but also by frequency dependent parameter mostly by L0 to L3 and C0 to C3 where L0 and C0 are not frequency dependent <<<<Alternative in air with VF=1 the exact one way travel is 3.335605mm/ps and by VF=0.7 4.765151mm/ps and for VF=0.695 4.799433mm/ps Again, apologies if these are very basic questions, I just want to get it as clear in my head as I can (given that I'm only as knowledgeable in math as the average person - I've a Masters degree in engineering, but my expertise lies in unrelated fields). Many thanks, Shabaz. ________________________________ From: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> on behalf of Kurt Poulsen < <mailto:kurt@...> kurt@...> Sent: 05 March 2024 19:38 To: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> Subject: Re: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi Shabaz UPS, here are the documents Kind regards Kurt -----Oprindelig meddelelse----- Fra: <mailto:[email protected]> [email protected] < <mailto:[email protected]> [email protected]> P? vegne af Shabaz Yousaf Sendt: 5. marts 2024 16:27 Til: <mailto:[email protected]> [email protected] Emne: [N2PK-VNA] SDR-Kits Female SMA Calibration Kit query Hi, I've purchased a SDR-Kits Female Calibration Kit of Rosenberger parts, it's intended for DG8SAQ VNWA, but I don't have that, I intend to use it with N2PK VNA, and R&S FPC1500 VNA. I had a question, which I'll eventually e-mail SDR-Kits with, but I thought it would be worth asking on the N2PK mailer first, since others may have done the same thing as me and obtained this. The question I have, is (perhaps a really basic one! in which case I apologize), in the screenshot in their datasheet, they show an offset delay, and a derived electrical length. A snippet from the datasheet is shown below; you can see the two-way delay of 84.70ps, and a one-way electrical length of 8.87mm. Using some simple math, I had previously believed that the offset delay can be converted to electrical length by multiplying by 0.3, i.e. 84.70ps would become 25.41mm, and half of that (since they are using two-way delay for some reason) would be 12.705mm. [cid:fd356d6e-2451-4e33-b967-7186a635a220] Link to the PDF full datasheet: <<<>>> <><><> I installed the VNWA software and entered the 84.7ps value myself, and it calculated 8.887 mm mechanical? length, so that settles that the datasheet has an older incorrect screenshot, which is minor but I'll raise it with them since it is confusing to readers. However, more importantly, I'm curious how the VNWA software arrived at that value anyway, because a conversion of 8.887 mm mechanical to electrical would be 1.5 times 8.887 which equals 13.33mm , but it's still quite different from my computation of 12.705mm. [cid:f102a3a1-f2fd-44a2-a45d-f69c90ba23ba] My question is, how did they come up with the electrical length? Am I calculating it wrong, or is the VNWA software calculating it wrong? It's important to me, because on my FPC1500 VNA, the only values I can enter are lengths, so I need to know if I should be typing 12.705, or 13.33, or something else! : ) [cid:8801385d-6178-4b9f-8cc4-f688d723556c] Personally, I believe it should be 12.705, because when I calibrate like that, I believe I'm getting decent measurements. But I'd like to know if this is just luck, or if I am actually using the correct formula. Any help would be gratefully appreciated. Many thanks, Shabaz. |
Kurt Poulsen
