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Recomendations for a VNA
Hi gang,
I know there are several professional engineering types on the list, so I thought I'd post this here. I teach at a technical college and it is budget time. My boss asked me for a "wish list" and a vector network analyzer came to mind. What I had in mind would be something we could use to characterize small signal BJT and JFET circuits at say 3-30MHz. VHF and UHF would be nice, but not required. I'd be looking for something that could provide real and imaginary values, so as to be able to develop s parameters for various circuits. In order to qualify for consideration, the unit would have to be new, and non-kit. :( I know HP and others make things like this. Any recommendations? BTW, I know something like this is going to run in the kilo or tens of kilo buck range. Hey, it's their money and they asked. ;) ;) ;) Thanks for the input. Bob WB0POQ |
"Bob Liesenfeld" wrote in message ... Hi gang, I know there are several professional engineering types on the list, so I thought I'd post this here. I teach at a technical college and it is budget time. My boss asked me for a "wish list" and a vector network analyzer came to mind. What I had in mind would be something we could use to characterize small signal BJT and JFET circuits at say 3-30MHz. VHF and UHF would be nice, but not required. I'd be looking for something that could provide real and imaginary values, so as to be able to develop s parameters for various circuits. In order to qualify for consideration, the unit would have to be new, and non-kit. :( I know HP and others make things like this. Any recommendations? BTW, I know something like this is going to run in the kilo or tens of kilo buck range. Hey, it's their money and they asked. ;) ;) ;) Thanks for the input. Bob WB0POQ Have a look at Paul's VNBA at: http://users.adelphia.net/~n2pk/ Accuracy is wonderful, software is elegant. These are being kitted in the $200 range. Don't let the price mislead you- this is a lab quality instrument. No affiliation, just admiration. Dale W4OP |
"Bob Liesenfeld" wrote in message ... Hi gang, I know there are several professional engineering types on the list, so I thought I'd post this here. I teach at a technical college and it is budget time. My boss asked me for a "wish list" and a vector network analyzer came to mind. What I had in mind would be something we could use to characterize small signal BJT and JFET circuits at say 3-30MHz. VHF and UHF would be nice, but not required. I'd be looking for something that could provide real and imaginary values, so as to be able to develop s parameters for various circuits. In order to qualify for consideration, the unit would have to be new, and non-kit. :( I know HP and others make things like this. Any recommendations? BTW, I know something like this is going to run in the kilo or tens of kilo buck range. Hey, it's their money and they asked. ;) ;) ;) Thanks for the input. Bob WB0POQ Have a look at Paul's VNBA at: http://users.adelphia.net/~n2pk/ Accuracy is wonderful, software is elegant. These are being kitted in the $200 range. Don't let the price mislead you- this is a lab quality instrument. No affiliation, just admiration. Dale W4OP |
It might be possible to find a donation, too, and of course that
wouldn't have to be new (but might be). My specific recommendations would be biased so I'm going to avoid giving them. However, I think you should make a wish-list of features, first, and perhaps your students could help you come up with those. It would even be a chance to engage them in a little research. I'd say you should have an instrument that's easy to learn and use, and that introduces the students to a good range of the capabilities of a good VNA. It would be good if it introduces them to the importance of calibration, and just _what_ should be calibrated on a VNA. It would be good if it can make s-parameter measurements. The concept of having the ability to make calibrated measurements at the end of a (possibly fairly long) transmission line is very useful. In actual use, I'd look for ways to illustrate that they (all of them) have limitations: there are tradeoffs in the design of a VNA, made with an eye to the intended application(s). I know that HP published some nice application notes about VNA applications and calibration and accuracy limits. Likely Rohde & Schwarz and Anritsu and others have similar ap notes. If you have trouble finding HP ones, I may be able to help, but they're likely on the Agilent web (somewhere). Also look for articles in the HP Journal...again, I can help if you can't find anything. Cheers, Tom Bob Liesenfeld wrote in message ... Hi gang, I know there are several professional engineering types on the list, so I thought I'd post this here. I teach at a technical college and it is budget time. My boss asked me for a "wish list" and a vector network analyzer came to mind. What I had in mind would be something we could use to characterize small signal BJT and JFET circuits at say 3-30MHz. VHF and UHF would be nice, but not required. I'd be looking for something that could provide real and imaginary values, so as to be able to develop s parameters for various circuits. In order to qualify for consideration, the unit would have to be new, and non-kit. :( I know HP and others make things like this. Any recommendations? BTW, I know something like this is going to run in the kilo or tens of kilo buck range. Hey, it's their money and they asked. ;) ;) ;) Thanks for the input. Bob WB0POQ |
It might be possible to find a donation, too, and of course that
wouldn't have to be new (but might be). My specific recommendations would be biased so I'm going to avoid giving them. However, I think you should make a wish-list of features, first, and perhaps your students could help you come up with those. It would even be a chance to engage them in a little research. I'd say you should have an instrument that's easy to learn and use, and that introduces the students to a good range of the capabilities of a good VNA. It would be good if it introduces them to the importance of calibration, and just _what_ should be calibrated on a VNA. It would be good if it can make s-parameter measurements. The concept of having the ability to make calibrated measurements at the end of a (possibly fairly long) transmission line is very useful. In actual use, I'd look for ways to illustrate that they (all of them) have limitations: there are tradeoffs in the design of a VNA, made with an eye to the intended application(s). I know that HP published some nice application notes about VNA applications and calibration and accuracy limits. Likely Rohde & Schwarz and Anritsu and others have similar ap notes. If you have trouble finding HP ones, I may be able to help, but they're likely on the Agilent web (somewhere). Also look for articles in the HP Journal...again, I can help if you can't find anything. Cheers, Tom Bob Liesenfeld wrote in message ... Hi gang, I know there are several professional engineering types on the list, so I thought I'd post this here. I teach at a technical college and it is budget time. My boss asked me for a "wish list" and a vector network analyzer came to mind. What I had in mind would be something we could use to characterize small signal BJT and JFET circuits at say 3-30MHz. VHF and UHF would be nice, but not required. I'd be looking for something that could provide real and imaginary values, so as to be able to develop s parameters for various circuits. In order to qualify for consideration, the unit would have to be new, and non-kit. :( I know HP and others make things like this. Any recommendations? BTW, I know something like this is going to run in the kilo or tens of kilo buck range. Hey, it's their money and they asked. ;) ;) ;) Thanks for the input. Bob WB0POQ |
I just got through building up the VNA that Dale mentioned. Kit price is 250
dollars, plus 5 dollars shipping in the USA. Right now, I am etching the power supply board, and I hope to have the unit up and running later this afternoon. Pete "Tom Bruhns" wrote in message m... It might be possible to find a donation, too, and of course that wouldn't have to be new (but might be). My specific recommendations would be biased so I'm going to avoid giving them. However, I think you should make a wish-list of features, first, and perhaps your students could help you come up with those. It would even be a chance to engage them in a little research. I'd say you should have an instrument that's easy to learn and use, and that introduces the students to a good range of the capabilities of a good VNA. It would be good if it introduces them to the importance of calibration, and just _what_ should be calibrated on a VNA. It would be good if it can make s-parameter measurements. The concept of having the ability to make calibrated measurements at the end of a (possibly fairly long) transmission line is very useful. In actual use, I'd look for ways to illustrate that they (all of them) have limitations: there are tradeoffs in the design of a VNA, made with an eye to the intended application(s). I know that HP published some nice application notes about VNA applications and calibration and accuracy limits. Likely Rohde & Schwarz and Anritsu and others have similar ap notes. If you have trouble finding HP ones, I may be able to help, but they're likely on the Agilent web (somewhere). Also look for articles in the HP Journal...again, I can help if you can't find anything. Cheers, Tom Bob Liesenfeld wrote in message ... Hi gang, I know there are several professional engineering types on the list, so I thought I'd post this here. I teach at a technical college and it is budget time. My boss asked me for a "wish list" and a vector network analyzer came to mind. What I had in mind would be something we could use to characterize small signal BJT and JFET circuits at say 3-30MHz. VHF and UHF would be nice, but not required. I'd be looking for something that could provide real and imaginary values, so as to be able to develop s parameters for various circuits. In order to qualify for consideration, the unit would have to be new, and non-kit. :( I know HP and others make things like this. Any recommendations? BTW, I know something like this is going to run in the kilo or tens of kilo buck range. Hey, it's their money and they asked. ;) ;) ;) Thanks for the input. Bob WB0POQ |
I just got through building up the VNA that Dale mentioned. Kit price is 250
dollars, plus 5 dollars shipping in the USA. Right now, I am etching the power supply board, and I hope to have the unit up and running later this afternoon. Pete "Tom Bruhns" wrote in message m... It might be possible to find a donation, too, and of course that wouldn't have to be new (but might be). My specific recommendations would be biased so I'm going to avoid giving them. However, I think you should make a wish-list of features, first, and perhaps your students could help you come up with those. It would even be a chance to engage them in a little research. I'd say you should have an instrument that's easy to learn and use, and that introduces the students to a good range of the capabilities of a good VNA. It would be good if it introduces them to the importance of calibration, and just _what_ should be calibrated on a VNA. It would be good if it can make s-parameter measurements. The concept of having the ability to make calibrated measurements at the end of a (possibly fairly long) transmission line is very useful. In actual use, I'd look for ways to illustrate that they (all of them) have limitations: there are tradeoffs in the design of a VNA, made with an eye to the intended application(s). I know that HP published some nice application notes about VNA applications and calibration and accuracy limits. Likely Rohde & Schwarz and Anritsu and others have similar ap notes. If you have trouble finding HP ones, I may be able to help, but they're likely on the Agilent web (somewhere). Also look for articles in the HP Journal...again, I can help if you can't find anything. Cheers, Tom Bob Liesenfeld wrote in message ... Hi gang, I know there are several professional engineering types on the list, so I thought I'd post this here. I teach at a technical college and it is budget time. My boss asked me for a "wish list" and a vector network analyzer came to mind. What I had in mind would be something we could use to characterize small signal BJT and JFET circuits at say 3-30MHz. VHF and UHF would be nice, but not required. I'd be looking for something that could provide real and imaginary values, so as to be able to develop s parameters for various circuits. In order to qualify for consideration, the unit would have to be new, and non-kit. :( I know HP and others make things like this. Any recommendations? BTW, I know something like this is going to run in the kilo or tens of kilo buck range. Hey, it's their money and they asked. ;) ;) ;) Thanks for the input. Bob WB0POQ |
On Wed, 11 Feb 2004 14:17:15 GMT, "Pete KE9OA"
wrote: I just got through building up the VNA that Dale mentioned. Kit price is 250 dollars, plus 5 dollars shipping in the USA. Right now, I am etching the power supply board, and I hope to have the unit up and running later this afternoon. Please let us know how you get on.... -- The BBC: Licensed at public expense to spread lies. |
On Wed, 11 Feb 2004 14:17:15 GMT, "Pete KE9OA"
wrote: I just got through building up the VNA that Dale mentioned. Kit price is 250 dollars, plus 5 dollars shipping in the USA. Right now, I am etching the power supply board, and I hope to have the unit up and running later this afternoon. Please let us know how you get on.... -- The BBC: Licensed at public expense to spread lies. |
Hi Paul,
I just finished it this evening......................it is a good piece of equipment, and worth the money. Tomorrow, I will do more in-depth testing. It appears to have resolution to 6 digits, which is good. It consists of a pair of 9851 DDS chips, with a 1496 being used as a direct conversion detector. I think I am going to build another one, so I can use one at home and one at work. Pete "Paul Burridge" wrote in message ... On Wed, 11 Feb 2004 14:17:15 GMT, "Pete KE9OA" wrote: I just got through building up the VNA that Dale mentioned. Kit price is 250 dollars, plus 5 dollars shipping in the USA. Right now, I am etching the power supply board, and I hope to have the unit up and running later this afternoon. Please let us know how you get on.... -- The BBC: Licensed at public expense to spread lies. |
Hi Paul,
I just finished it this evening......................it is a good piece of equipment, and worth the money. Tomorrow, I will do more in-depth testing. It appears to have resolution to 6 digits, which is good. It consists of a pair of 9851 DDS chips, with a 1496 being used as a direct conversion detector. I think I am going to build another one, so I can use one at home and one at work. Pete "Paul Burridge" wrote in message ... On Wed, 11 Feb 2004 14:17:15 GMT, "Pete KE9OA" wrote: I just got through building up the VNA that Dale mentioned. Kit price is 250 dollars, plus 5 dollars shipping in the USA. Right now, I am etching the power supply board, and I hope to have the unit up and running later this afternoon. Please let us know how you get on.... -- The BBC: Licensed at public expense to spread lies. |
On Thu, 12 Feb 2004 01:51:41 GMT, "Pete KE9OA"
wrote: Hi Paul, I just finished it this evening......................it is a good piece of equipment, and worth the money. Tomorrow, I will do more in-depth testing. It appears to have resolution to 6 digits, which is good. It consists of a pair of 9851 DDS chips, with a 1496 being used as a direct conversion detector. I think I am going to build another one, so I can use one at home and one at work. Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... -- The BBC: Licensed at public expense to spread lies. |
On Thu, 12 Feb 2004 01:51:41 GMT, "Pete KE9OA"
wrote: Hi Paul, I just finished it this evening......................it is a good piece of equipment, and worth the money. Tomorrow, I will do more in-depth testing. It appears to have resolution to 6 digits, which is good. It consists of a pair of 9851 DDS chips, with a 1496 being used as a direct conversion detector. I think I am going to build another one, so I can use one at home and one at work. Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... -- The BBC: Licensed at public expense to spread lies. |
Paul Burridge wrote:
On Thu, 12 Feb 2004 01:51:41 GMT, "Pete KE9OA" wrote: Hi Paul, I just finished it this evening......................it is a good piece of equipment, and worth the money. Tomorrow, I will do more in-depth testing. It appears to have resolution to 6 digits, which is good. It consists of a pair of 9851 DDS chips, with a 1496 being used as a direct conversion detector. I think I am going to build another one, so I can use one at home and one at work. Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. N2PK's website (www.qsl.net/n2pk) gives exhaustive information about measurement accuracy, standards and comparisons with professional VNAs. When used correctly (a necessity for any VNA), N2PK's instrument is so accurate that he had to go to extreme lengths to find any real differences from commercial equipment. For example, the measured signal magnitude tracks a 'standard' step attenuator to better than 0.1dB over a 90dB range... but which is in error, the VNA or the attenuator? At those levels of performance, it's almost impossible to tell. Bottom line: you'll hardly ever need to worry about accuracy as such, only about using the instrument correctly. The only minor drawbacks are a small amount of thermal drift (because this is a DC-coupled system) and the possibilities of responding to DDS harmonics and spurs; all of these are very thoroughly documented. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... Having had one running for about six months, I can confirm it's excellent. Far from being infrequently-needed, it has become one of those instruments I couldn't possibly manage without! Read the documentation and you'll see exactly why. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Paul Burridge wrote:
On Thu, 12 Feb 2004 01:51:41 GMT, "Pete KE9OA" wrote: Hi Paul, I just finished it this evening......................it is a good piece of equipment, and worth the money. Tomorrow, I will do more in-depth testing. It appears to have resolution to 6 digits, which is good. It consists of a pair of 9851 DDS chips, with a 1496 being used as a direct conversion detector. I think I am going to build another one, so I can use one at home and one at work. Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. N2PK's website (www.qsl.net/n2pk) gives exhaustive information about measurement accuracy, standards and comparisons with professional VNAs. When used correctly (a necessity for any VNA), N2PK's instrument is so accurate that he had to go to extreme lengths to find any real differences from commercial equipment. For example, the measured signal magnitude tracks a 'standard' step attenuator to better than 0.1dB over a 90dB range... but which is in error, the VNA or the attenuator? At those levels of performance, it's almost impossible to tell. Bottom line: you'll hardly ever need to worry about accuracy as such, only about using the instrument correctly. The only minor drawbacks are a small amount of thermal drift (because this is a DC-coupled system) and the possibilities of responding to DDS harmonics and spurs; all of these are very thoroughly documented. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... Having had one running for about six months, I can confirm it's excellent. Far from being infrequently-needed, it has become one of those instruments I couldn't possibly manage without! Read the documentation and you'll see exactly why. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... Paul, what part of the comparison between my Boonton and the N2PK VNA do you have a difficult time with? Or for that matter, the comparisons with Chip Owens HP 5783C? The accuracy is primarily limited by the quality of the OSL standards used in setup, and the experience of the user in establishing his/her reference plane. W4ZCB |
Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... Paul, what part of the comparison between my Boonton and the N2PK VNA do you have a difficult time with? Or for that matter, the comparisons with Chip Owens HP 5783C? The accuracy is primarily limited by the quality of the OSL standards used in setup, and the experience of the user in establishing his/her reference plane. W4ZCB |
I did play with it today, sweeping a couple of filters. The unit is amazing!
I understand that one fellow in England is developing Windows based software to control this unit. I am pretty excited about that. I don't have any suitable transfer standards for checking the accuracy of this instrument, but the designer has done a very good job of characterizing this unit. See the following posts. One more thing.............I think you would be very happy with this unit. Pete "Paul Burridge" wrote in message ... On Thu, 12 Feb 2004 01:51:41 GMT, "Pete KE9OA" wrote: Hi Paul, I just finished it this evening......................it is a good piece of equipment, and worth the money. Tomorrow, I will do more in-depth testing. It appears to have resolution to 6 digits, which is good. It consists of a pair of 9851 DDS chips, with a 1496 being used as a direct conversion detector. I think I am going to build another one, so I can use one at home and one at work. Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... -- The BBC: Licensed at public expense to spread lies. |
I did play with it today, sweeping a couple of filters. The unit is amazing!
I understand that one fellow in England is developing Windows based software to control this unit. I am pretty excited about that. I don't have any suitable transfer standards for checking the accuracy of this instrument, but the designer has done a very good job of characterizing this unit. See the following posts. One more thing.............I think you would be very happy with this unit. Pete "Paul Burridge" wrote in message ... On Thu, 12 Feb 2004 01:51:41 GMT, "Pete KE9OA" wrote: Hi Paul, I just finished it this evening......................it is a good piece of equipment, and worth the money. Tomorrow, I will do more in-depth testing. It appears to have resolution to 6 digits, which is good. It consists of a pair of 9851 DDS chips, with a 1496 being used as a direct conversion detector. I think I am going to build another one, so I can use one at home and one at work. Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... -- The BBC: Licensed at public expense to spread lies. |
Agreed.....................a super good unit.
Pete "Harold E. Johnson" wrote in message news:bJRWb.300189$na.451700@attbi_s04... Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... Paul, what part of the comparison between my Boonton and the N2PK VNA do you have a difficult time with? Or for that matter, the comparisons with Chip Owens HP 5783C? The accuracy is primarily limited by the quality of the OSL standards used in setup, and the experience of the user in establishing his/her reference plane. W4ZCB |
Agreed.....................a super good unit.
Pete "Harold E. Johnson" wrote in message news:bJRWb.300189$na.451700@attbi_s04... Thanks, Pete. Resolution is one thing, accuracy is another. Do you have a proprietory instrument within calibration to compare it against? I want to believe in this kit. If it works as advertised then it's a significant breakthrough for those of us who feel reluctant to part with 20,000 quid for a piece of relatively infrequently-needed test equipment! Please report back here when you've had the chance to check it out properly and let us know how it performs... Paul, what part of the comparison between my Boonton and the N2PK VNA do you have a difficult time with? Or for that matter, the comparisons with Chip Owens HP 5783C? The accuracy is primarily limited by the quality of the OSL standards used in setup, and the experience of the user in establishing his/her reference plane. W4ZCB |
On Thu, 12 Feb 2004 19:52:26 +0000, "Ian White, G3SEK"
wrote: Having had one running for about six months, I can confirm it's excellent. Far from being infrequently-needed, it has become one of those instruments I couldn't possibly manage without! Read the documentation and you'll see exactly why. I shall. And thanks for the info! I didn't realise you'd bought the kit. Did you have to have it shipped over from the States? I assume there's no outlet for them here, as yet at any rate. What's the UK price inc.shipping? (Just in case I can't find those details on the site). -- The BBC: Licensed at public expense to spread lies. |
On Thu, 12 Feb 2004 19:52:26 +0000, "Ian White, G3SEK"
wrote: Having had one running for about six months, I can confirm it's excellent. Far from being infrequently-needed, it has become one of those instruments I couldn't possibly manage without! Read the documentation and you'll see exactly why. I shall. And thanks for the info! I didn't realise you'd bought the kit. Did you have to have it shipped over from the States? I assume there's no outlet for them here, as yet at any rate. What's the UK price inc.shipping? (Just in case I can't find those details on the site). -- The BBC: Licensed at public expense to spread lies. |
Paul Burridge wrote:
On Thu, 12 Feb 2004 19:52:26 +0000, "Ian White, G3SEK" wrote: Having had one running for about six months, I can confirm it's excellent. Far from being infrequently-needed, it has become one of those instruments I couldn't possibly manage without! Read the documentation and you'll see exactly why. I shall. And thanks for the info! I didn't realise you'd bought the kit. Did you have to have it shipped over from the States? I assume there's no outlet for them here, as yet at any rate. What's the UK price inc.shipping? (Just in case I can't find those details on the site). At the time, there wasn't a kit as such, but the parts cost about £100 in total (not including the DDS ICs, which Analog Devices generously supply free to amateurs as 'samples'). However, certain parts are only obtainable in the USA, so people in Europe are getting together to buy in bulk. I don't have any specific information about that, but a mailing-list is to be started shortly (wait for the announcement) so that will be a focal point for people to co-ordinate their buying. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Paul Burridge wrote:
On Thu, 12 Feb 2004 19:52:26 +0000, "Ian White, G3SEK" wrote: Having had one running for about six months, I can confirm it's excellent. Far from being infrequently-needed, it has become one of those instruments I couldn't possibly manage without! Read the documentation and you'll see exactly why. I shall. And thanks for the info! I didn't realise you'd bought the kit. Did you have to have it shipped over from the States? I assume there's no outlet for them here, as yet at any rate. What's the UK price inc.shipping? (Just in case I can't find those details on the site). At the time, there wasn't a kit as such, but the parts cost about £100 in total (not including the DDS ICs, which Analog Devices generously supply free to amateurs as 'samples'). However, certain parts are only obtainable in the USA, so people in Europe are getting together to buy in bulk. I don't have any specific information about that, but a mailing-list is to be started shortly (wait for the announcement) so that will be a focal point for people to co-ordinate their buying. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
On Thu, 12 Feb 2004 19:52:26 +0000, "Ian White, G3SEK"
wrote: Having had one running for about six months, I can confirm it's excellent. Far from being infrequently-needed, it has become one of those instruments I couldn't possibly manage without! Read the documentation and you'll see exactly why. Okay, I've read the dox but am still in the dark as to what *you* use yours for. What makes it so indispensible? -- The BBC: Licensed at public expense to spread lies. |
On Thu, 12 Feb 2004 19:52:26 +0000, "Ian White, G3SEK"
wrote: Having had one running for about six months, I can confirm it's excellent. Far from being infrequently-needed, it has become one of those instruments I couldn't possibly manage without! Read the documentation and you'll see exactly why. Okay, I've read the dox but am still in the dark as to what *you* use yours for. What makes it so indispensible? -- The BBC: Licensed at public expense to spread lies. |
Okay, I've read the dox but am still in the dark as to what *you* use yours for. What makes it so indispensible? When was the last time you needed to know a capacitor value AT the frequency you're going to use it at? (the "C" minus the "L" of the leads) Or the passband of a filter and it's IL and it's skirts and it's blowby and it's group delay and it's terminating impedances? Or needed dual high level isolated oscillators to make Ip3 measurements on a receiver or transmitter? Or have a precision sweep generator and trigger for a Spectrum Analyzer? Or needed the inductance of an inductor AT the operating frequency? (The "L" less the "C") Or needed the series and parallel resonant frquencies of a crystal and the Rs of same and it's "Q"? Or needed the "S" parameters of a small signal transistor? Or wanted to know the impedance of your antenna at the shack end of the coax. Or, if you were smart enough to log the length of coax when you installed it, the impedance AT the antenna? Or needed the Zo of a length of coax? Or the gain of an amplifier over it's frequency range and it's 3 dB corners to the 0.01 dB? Or needed a quadrature signal source to be the LO of that new I-Q receiver? Or-or-or It's a lab in a box. W4ZCB |
Okay, I've read the dox but am still in the dark as to what *you* use yours for. What makes it so indispensible? When was the last time you needed to know a capacitor value AT the frequency you're going to use it at? (the "C" minus the "L" of the leads) Or the passband of a filter and it's IL and it's skirts and it's blowby and it's group delay and it's terminating impedances? Or needed dual high level isolated oscillators to make Ip3 measurements on a receiver or transmitter? Or have a precision sweep generator and trigger for a Spectrum Analyzer? Or needed the inductance of an inductor AT the operating frequency? (The "L" less the "C") Or needed the series and parallel resonant frquencies of a crystal and the Rs of same and it's "Q"? Or needed the "S" parameters of a small signal transistor? Or wanted to know the impedance of your antenna at the shack end of the coax. Or, if you were smart enough to log the length of coax when you installed it, the impedance AT the antenna? Or needed the Zo of a length of coax? Or the gain of an amplifier over it's frequency range and it's 3 dB corners to the 0.01 dB? Or needed a quadrature signal source to be the LO of that new I-Q receiver? Or-or-or It's a lab in a box. W4ZCB |
Harold E. Johnson wrote:
Okay, I've read the dox but am still in the dark as to what *you* use yours for. What makes it so indispensible? When was the last time you needed to know a capacitor value AT the frequency you're going to use it at? (the "C" minus the "L" of the leads) Or the passband of a filter and it's IL and it's skirts and it's blowby and it's group delay and it's terminating impedances? Or needed dual high level isolated oscillators to make Ip3 measurements on a receiver or transmitter? Or have a precision sweep generator and trigger for a Spectrum Analyzer? Or needed the inductance of an inductor AT the operating frequency? (The "L" less the "C") Or needed the series and parallel resonant frquencies of a crystal and the Rs of same and it's "Q"? Or needed the "S" parameters of a small signal transistor? Or wanted to know the impedance of your antenna at the shack end of the coax. Or, if you were smart enough to log the length of coax when you installed it, the impedance AT the antenna? Or needed the Zo of a length of coax? Or the gain of an amplifier over it's frequency range and it's 3 dB corners to the 0.01 dB? Or needed a quadrature signal source to be the LO of that new I-Q receiver? Or-or-or It's a lab in a box. W4ZCB Thanks to the US-Europe time difference, Harold has left me very little to add this morning! We could also think of it in terms of the other instruments that the VNA can replace - or beat, because it gives full vector (R-X etc) information. Using only its reflection functions, the VNA can replace all of the following: an MFJ, Autek or AEA computing antenna analyser; an LF LCR bridge; a Q meter; an HF R-X impedance bridge; and an HF return loss bridge. As Harold pointed out, the twin DDS signal sources can replace an HF sweeper or a medium-quality HF signal generator - or two of each, if necessary. The transmission measurement functions - magnitude and phase, with a dynamic range of at least 90dB - are something I just didn't have. Several months ago, Harold described an excellent practical example of designing and building a crystal filter. This goes in five steps: 1. Rough out the design using available software. 2. Take a pile of cheap crystals and measure their individual characteristics, on-frequency, using the VNA. Select the best ones for the filter you want to build. 3. Refine the filter design according to the actual component measurements, and use simulation software to predict how it's going to work. Adjust other component values as required. 4. Build the filter. There is no alignment - steps 2 and 3 replaced all that. 5. Use the VNA to confirm that it works exactly as predicted. Have lunch. You can see those results in the VNA documentation. This is the professional approach to RF design: compute, measure components, compute again, and build... and it *will* work, because you've left almost nothing to chance. Until now, this approach had not been open to amateurs because we didn't have the necessary test equipment. To me, that is the real power of this instrument. For some years, I've been trying to develop this approach, but have had to rely on the goodwill of a friend who could make measurements using his lab VNA at work. But obviously there have been limitations on the kinds of things that could be measured - they had to be small enough to fit in a briefcase, and they had to be completed to the extent that they were plug-and-play - so there have been no antenna measurements, and no measurements on work in progress. I'm free from those limitations now, up to at least 50MHz... and the way is being opened to make equally good measurements on the higher amateur bands. Meanwhile my friend has noticed that he won't have access to the lab forever, so guess what - he has built himself an N2PK VNA too! Like N2PK, we're struggling to identify any significant differences in accuracy between the two instruments. A compact, lightweight and inexpensive VNA also opens up completely new possibilities for field measurements that even a commercial VNA cannot make, because it's too big, heavy, delicate and valuable to be moved out of the lab. When the weather improves, I plan to take the N2PK VNA outside with a laptop and a small battery pack, and to do some really detailed antenna work. Of the three objects to be carried around, by far the smallest and lightest will be the VNA. I hope that gives you a real picture of the new possibilities that are opening up. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Harold E. Johnson wrote:
Okay, I've read the dox but am still in the dark as to what *you* use yours for. What makes it so indispensible? When was the last time you needed to know a capacitor value AT the frequency you're going to use it at? (the "C" minus the "L" of the leads) Or the passband of a filter and it's IL and it's skirts and it's blowby and it's group delay and it's terminating impedances? Or needed dual high level isolated oscillators to make Ip3 measurements on a receiver or transmitter? Or have a precision sweep generator and trigger for a Spectrum Analyzer? Or needed the inductance of an inductor AT the operating frequency? (The "L" less the "C") Or needed the series and parallel resonant frquencies of a crystal and the Rs of same and it's "Q"? Or needed the "S" parameters of a small signal transistor? Or wanted to know the impedance of your antenna at the shack end of the coax. Or, if you were smart enough to log the length of coax when you installed it, the impedance AT the antenna? Or needed the Zo of a length of coax? Or the gain of an amplifier over it's frequency range and it's 3 dB corners to the 0.01 dB? Or needed a quadrature signal source to be the LO of that new I-Q receiver? Or-or-or It's a lab in a box. W4ZCB Thanks to the US-Europe time difference, Harold has left me very little to add this morning! We could also think of it in terms of the other instruments that the VNA can replace - or beat, because it gives full vector (R-X etc) information. Using only its reflection functions, the VNA can replace all of the following: an MFJ, Autek or AEA computing antenna analyser; an LF LCR bridge; a Q meter; an HF R-X impedance bridge; and an HF return loss bridge. As Harold pointed out, the twin DDS signal sources can replace an HF sweeper or a medium-quality HF signal generator - or two of each, if necessary. The transmission measurement functions - magnitude and phase, with a dynamic range of at least 90dB - are something I just didn't have. Several months ago, Harold described an excellent practical example of designing and building a crystal filter. This goes in five steps: 1. Rough out the design using available software. 2. Take a pile of cheap crystals and measure their individual characteristics, on-frequency, using the VNA. Select the best ones for the filter you want to build. 3. Refine the filter design according to the actual component measurements, and use simulation software to predict how it's going to work. Adjust other component values as required. 4. Build the filter. There is no alignment - steps 2 and 3 replaced all that. 5. Use the VNA to confirm that it works exactly as predicted. Have lunch. You can see those results in the VNA documentation. This is the professional approach to RF design: compute, measure components, compute again, and build... and it *will* work, because you've left almost nothing to chance. Until now, this approach had not been open to amateurs because we didn't have the necessary test equipment. To me, that is the real power of this instrument. For some years, I've been trying to develop this approach, but have had to rely on the goodwill of a friend who could make measurements using his lab VNA at work. But obviously there have been limitations on the kinds of things that could be measured - they had to be small enough to fit in a briefcase, and they had to be completed to the extent that they were plug-and-play - so there have been no antenna measurements, and no measurements on work in progress. I'm free from those limitations now, up to at least 50MHz... and the way is being opened to make equally good measurements on the higher amateur bands. Meanwhile my friend has noticed that he won't have access to the lab forever, so guess what - he has built himself an N2PK VNA too! Like N2PK, we're struggling to identify any significant differences in accuracy between the two instruments. A compact, lightweight and inexpensive VNA also opens up completely new possibilities for field measurements that even a commercial VNA cannot make, because it's too big, heavy, delicate and valuable to be moved out of the lab. When the weather improves, I plan to take the N2PK VNA outside with a laptop and a small battery pack, and to do some really detailed antenna work. Of the three objects to be carried around, by far the smallest and lightest will be the VNA. I hope that gives you a real picture of the new possibilities that are opening up. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
On Fri, 13 Feb 2004 09:01:38 +0000, "Ian White, G3SEK"
wrote: Harold E. Johnson wrote: [snip] I hope that gives you a real picture of the new possibilities that are opening up. [snip] Thanks, both! Sounds like a must-have now you've explained all these remarkable capabilities. I shall await developments on parts availability with great interest.... -- The BBC: Licensed at public expense to spread lies. |
On Fri, 13 Feb 2004 09:01:38 +0000, "Ian White, G3SEK"
wrote: Harold E. Johnson wrote: [snip] I hope that gives you a real picture of the new possibilities that are opening up. [snip] Thanks, both! Sounds like a must-have now you've explained all these remarkable capabilities. I shall await developments on parts availability with great interest.... -- The BBC: Licensed at public expense to spread lies. |
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