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S11 and S22 comparisons on 8753
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Hi Dave:
I stand corrected, you can not measure phase angle with a SNA, but you can make a more accurate |S11| measurement with the SNA. An air line is very different from a sliding load. If a sliding load is used as part of the VNA calibration the resulting measurement will be better than the common OSL type cal. Note, VNA cal standards come with data, but the data is generic to the model number of the set, NOT to the serial number, hence you can call up cal standards in the CAL menu of the VNA. There's a Wiltron (Anritsu) app note "Reflectometer Measurements - Revisited" (11410-00214) on using the air line and mismatched load to determine reflectometer directivity. From the app note: "The effective directivity after a broadband load calibration is essentially equal to the return loss of the load used for calibration. Unless the user is certain that the return loss of the load is at least 15 dB greater than return loss of devices to be measured, significant errors can result. Sliding loads are recommended for calibration and VNA test port specifications are based upon sliding load calibrations." So, if the desired impedance of the DUT is 50.0 +0j then using the airline measurement method with a SNA will give more accurate results. -- Have Fun, Brooke Clarke, N6GCE |
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David Kirkby
On 25 December 2012 03:17, Peter Gottlieb <hpnpilot@...> wrote:
And I'm sure the thing is completely unrepairable except by Agilent, schematicsI suspect you are probably right about it being unrepairable except by Agilent. I've not looked, but I doubt schematics are available now, but perhaps they might be when is 20 years out of support. once it goes out of support that is basically the end of that.Agilent will attempt to repair items that are out of support. I have an HP 8720D VNA that has been out of support for quite some time, but when I contacted Agilent about a repair a few months back, they said they could probably fix it, and could give me an approximate cost. They also offered to look at it free. In my case, the fault was obvious - it was a damaged thread on the 3.5 mm test port. Lucily it was not on the thread used for the RF measurement, but a secondly thread used to provide extra support to the Agilent test port cables with the large NMD conectors. The test port has both an internal and external thread. There's a picture of the damage here: Agilent intended replacing the whole coupler, which was going to cost around ?3000 ($5000) with labour. However, Joel Dunsmore, the Agilent VNA guru, said on that forum that one could try repairing the damaged bit of thread with a Dremmel. In fact my friend repaired it for me using a needle file at a cost to me of buying the needle files from eBay of around ?5 ($8). No, me neither. It will have to wait until I get paid my next monthsI don't have quite $800k to blow this week after buying Christmas salary, which might be a few months as I'm unemployed at the minute! Dave
Agilent sell a VNA for 110 GHz. At $691,437 for a 4-port model, I |
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J. Forster
Dr. Joel is a great, helpful guy.
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Merry Christmas all, -John ============== On 25 December 2012 03:17, Peter Gottlieb <hpnpilot@...> wrote:And I'm sure the thing is completely unrepairable except by Agilent,I suspect you are probably right about it being unrepairable except by |
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Am 25.12.2012 um 10:46 schrieb David Kirkby <david.kirkby@...>:
I hope you find such a well paid job. In the unlikely event that you need an assistent I would work for you for a small fraction of it. I am an engineer (rf and communication) and graduated from TH Darmstadt 32 years ago.No, me neither. It will have to wait until I get paid my next monthsI don't have quite $800k to blow this week after buying Christmas Merry Christmas Heinz |
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David Kirkby
On 25 December 2012 14:23, J. Forster <jfor@...> wrote:
Dr. Joel is a great, helpful guy.I agree with you John, in that Joel is very helpful. This help not only extends to someone owning the latest and greatest VNAs, but people like myself who own obsolete HP kit. His suggest to repair the thread, rather than pay a fortune to get the whole coupler replaced, saved me a lot of money. The US dealer I purchased this from offered to get it repaired, but that repair was changing the test port, not the whole coupler. I had concerns about that, as the tollerence in replacing just the test port is very stringent. IIRC, it has to be aligned to 0.0001". I would not trust anyone other than Agilent to do that job. Anyway, the VNA appears to work well now. I've been making measurement with it this morning - one way to spend Christmas day!! Dave. |
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