| Products > Test Equipment |
| Kirkby calibration kit alternatives? |
| << < (32/44) > >> |
| sixtimesseven:
Sorry for hacking this thread, but what do you guys think about the possible cal kit options for a HP3577A with S-Parameter test set (100khz-200Mhz, 50Ohms)? The Kirkby Kit with 7GHz seems to be overkill for me at the moment :( Thanks |
| TheSteve:
DIY is totally possible but he will still need someone to measure them for him. |
| drkirkby:
--- Quote from: rfspezi on March 19, 2018, 08:06:25 pm ---I could need some advice on what i am doing wrong with my Kirkby cal-kit. (Please appologise stupid questions, since VNA measurements are totally new to me --- End quote --- If you need advice on the use of our kit, please contact us, but I will answer them best I can here. --- Quote from: rfspezi on March 19, 2018, 08:06:25 pm ---On the floppy disk there are 3 files (SMA, SMA_M_M, SMA_F_F). I selected "SMA" and loaded it with "RECALL STATE". Is that the correct file to choose? After that, the frequency range is automatically changed to 300 kHz ... 3 GHz. Shouldn't it be set to the full range of 30 kHz - 6 GHz of my VNA? --- End quote --- I put the answer why your VNA is set from 300 kHz to 3 GHz in our FAQ. https://www.kirkbymicrowave.co.uk/Support/FAQ/Quick-questions-about-vector-network-analyzers/#Frequency-is-3-GHz-on-6-GHz-VNA The short answer is we write the coefficients using a 3 GHz 8753ES. The calibration standards are not measured on the 3 GHz VNA, but using the 3 GHz 8753ES it is just a convenient way for us to write the floppy disks. The standards are measured on a 20 GHz VNA (8720D) with a 26.5 GHz calibration kit (85052B). As for the correct file to load (SMA, SMA_F_F or SMA_M_M), it does not matter for 1-port calibrations. For 2-port calibrations it does, as the different files each have a different delay on the thru standard. An explanation is at https://www.kirkbymicrowave.co.uk/Support/FAQ/What-file-should-I-load-from-the-floppy-disk-into-the-VNA/ --- Quote from: rfspezi on March 19, 2018, 08:06:25 pm ---P.S.: Another thing that irritates me is that the 50 Ohm references are 49,5 and 51,1 Ohm instead of "50,0". I would expect to get better quality references for that price? --- End quote --- A low frequency (DC) resistance of 49.5 ohms, the VSWR is 50/49/5=1.0101 (return loss 46.0 dB), which is no worst than the return loss of the loads in the Keysight 85052B (US$ 12,956 in July 2018) 3.5 mm calibration kit. A DC resistance 49.5 ohms would not be out of specification in that kit. Now 51.1 ohms is a VSWR of 51.1/50 = 1.022 (return loss 39.3 dB), which is within the specification of our kit (> 32 dB return loss to 7 GHz), but not the 85052B, but then our kits do not cost almost $13,000. (For the 8, 10 and 12 GHz version of the SMA kit, the return loss of the loads will be at least 32 dB at 8, 10 or 12 GHz respectively) What we care about is the RF performance of the kit. If the loads were made from wirewound resistors, as standard resistors usually are, the DC resistance could be made very close to 50 ohms, but the RF performance would be appalling. You might note there's no specification for the DC resistance of RF terminations in any of the Keysight calibration kits, nor in the loads from companies like Minicircuits. It really is irrelevant. We have a HP 3457A 6.5 digit multi-meter here, which we had calibrated by Keysight only a month or two ago. It supports 4-wire resistance measurements. We could easily measure the DC resistance of the loads, but tests performed in the past indicate there's no correlation between DC resistance and microwave performance. So worrying about DC resistance is pointless. Loads are screened based on their RF performance, not the DC resistance. Dr. David Kirkby Kirkby Microwave Ltd. |
| G0HZU:
--- Quote ---What we care about is the RF performance of the kit. If the loads were made from wirewound resistors, as standard resistors usually are, the DC resistance could be made very close to 50 ohms, but the RF performance would be appalling. You might note there's no specification for the DC resistance of RF terminations in any of the Keysight calibration kits, nor in the loads from companies like Minicircuits. It really is irrelevant. --- End quote --- Hmm... I think you are trying to justify your use of a low cost wideband SMA 50R 'termination' here rather than the type of precision 50R load found in an expensive commercial RF cal kit. I don't 'test' HP/Agilent/Keysight cal kits very often but usually the performance/agreement between our kits at work (at LF) is excellent and this implies the LF resistance must be very close to 50R. When I made my homebrew SMA cal kit many years ago I tried to get as close to 50R on a DMM (at DC) as possible so spent some time selecting the best resistors to use. This cal kit always gives extremely good agreement at LF with a proper cal kit from Agilent so I think all the works Agilent/Keysight kits (and my homebrew kit) are very close to 50R at LF (eg at test frequencies <10MHz). I'd like to think they are all within about 0.1 to 0.2R of 50R at LF but I've never tried this test to prove it. I also have a Suhner (18GHz) SMA load here that I selected from a batch to be the closest to 50R (on a DMM) I could find. I sometimes use this instead of my homebrew SMA load.At work I think we have about a dozen 85033E 3.5mm kits and various 13-26GHz Ecal modules and a couple of 85032F N kits. However, I haven't tested all of them for LF performance. I have checked a few of them though... So a cal kit load that measures 51.1R at LF is an 'unusual case' in my experience. The Ecal kits will be corrected in a lookup table to be very close to 50R at LF although the only Ecal module I've tested extensively is my own one here at home. It usually agrees within a few tens of milliohms of 50R at LF compared to my homebrew cal kit and the hand selected Suhner 18GHz SMA load. The Suhner load and my homebrew SMA load have been tested in the past against an 85033E cal kit and I got similar agreement. So I generally take it for granted that a commercial cal kit will be very close to 50R at LF even though this isn't quoted in the datasheet. |
| G0HZU:
Here's an old plot of my Suhner 18GHz SMA load showing the LF performance. This load was hand selected from a large batch of identical Suhner 18GHz loads to be the closest to 50R and I just measured it again this evening (after many years) and it is 49.99R at DC on a Keithley 2000 4W meter. This plot was taken at work (a few years ago) using an 85033E cal kit and the VNA was a 6GHz 8753ES. It shows very close agreement with 50R all the way up to 200MHz. So this implies the 8753ES/85033E can measure a real 50R quite accurately. On my VNA here at home (using my N4431B-60006 Ecal to calibrate the VNA) the same Suhner 18GHz load measures 49.94R at LF. So pretty close to 50R again! I also dug out another Suhner 18GHz load and it measured 49.87R on the VNA (with the same Ecal calibration) across about 2-10MHz. On the 4W Keithley this second Suhner load measured 49.89R at DC. So good agreement again I think. |
| Navigation |
| Message Index |
| Next page |
| Previous page |