开云体育

The Agilent/Keysight FieldFox range are in theory great analyzers, although
they are pricey. The N9912A is very poor though.

The FirldFox range have an interesting calibration method called
“Quickcal”, which requires no calibration kit - you just leave the cable
open. It is not as good as using a calibration kit, but it has the
advantage of simplicity if used in the field.

You need to enter the type and gender of the connector, then it does its
magic. For return losses of > 14 dB, it is beneficial, but not essential to
use a load too, but that load doesn’t need to be very good.

The method used is proprietary, but a bug reported to the Keysight forum,
and the answer supplied by Keysight, gives one a clue how it works.

Clearly the method had a model of the open connector, the mere fact that
one needs to enter the type and gender of the connector. The bug reported,
and the answer received, suggest that the method makes use of time domain
data. I am guessing that the FieldFox measures the time to return from the
discontinuity in impedance.

The method works for N, 7-16 and female SMA or 3.5 mm. It is not
recommended for male SMA. It doesn’t work for APC7, but I suspect that is
simply because Keysight do not believe people will want to use a rough
calibration method on a precision laboratory connector. An APC7 connector
would be very easy to model.

Long term, it would be a useful addition to the NanoVNA firmware, but it
would be well down the priority list.

Dave.


--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom

It sounds like the kind of thing that would be patented. Maybe US6643597B1
is related?

Expired patents can be potential sources for how to do some of these things.

--
Rune / 5Q5R

On Mon, 16 Sep 2019, 00:18 Dr. David Kirkby from Kirkby Microwave Ltd, <
drkirkby@...> wrote:

The Agilent/Keysight FieldFox range are in theory great analyzers, although
they are pricey. The N9912A is very poor though.

The FirldFox range have an interesting calibration method called
“Quickcal”, which requires no calibration kit - you just leave the cable
open. It is not as good as using a calibration kit, but it has the
advantage of simplicity if used in the field.

You need to enter the type and gender of the connector, then it does its
magic. For return losses of > 14 dB, it is beneficial, but not essential to
use a load too, but that load doesn’t need to be very good.

The method used is proprietary, but a bug reported to the Keysight forum,
and the answer supplied by Keysight, gives one a clue how it works.

Clearly the method had a model of the open connector, the mere fact that
one needs to enter the type and gender of the connector. The bug reported,
and the answer received, suggest that the method makes use of time domain
data. I am guessing that the FieldFox measures the time to return from the
discontinuity in impedance.

The method works for N, 7-16 and female SMA or 3.5 mm. It is not
recommended for male SMA. It doesn’t work for APC7, but I suspect that is
simply because Keysight do not believe people will want to use a rough
calibration method on a precision laboratory connector. An APC7 connector
would be very easy to model.

Long term, it would be a useful addition to the NanoVNA firmware, but it
would be well down the priority list.

Dave.


--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom

On Mon, 16 Sep 2019 at 06:30, Rune Broberg <mihtjel@...> wrote:

It sounds like the kind of thing that would be patented. Maybe US6643597B1
is related?

Expired patents can be potential sources for how to do some of these
things.

--
Rune / 5Q5R

Yes, I could see a method like Quickcal could be patented. I can see an
obvious need to do that it you are producing hardware which is easily
copied. I am no expert, but it might be better not to disclose software
ideas, as you can bet that the Chinese will just ignore such patents.

I must admit to being confused by the US patent US6643597B1. I will need to
read it 100 times over to make any sense of it. At first glance it seems to
suggest that one doesn’t needs a calibration kit.


I don’t know what the position is regarding patents and non-commercial
products, or products that are sold commercially, but for which others have
developed GPL software. *Either way, I think the Chinese will ignore any
patent. *

The FieldFox instruments (perhaps with the exception of the brain dead
N9912A) don’t need a calibration kit to make measurements on the ports as
they are calibrated there. This was the post that got me thinking Quickcal
was implemented by a time domain transfer but looking at it again, I
don’t see why I assumed that



Quickcal relies on one having a good knowledge of the connector, as you
need to enter it - both the type and gender.

Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales.
Company number 08914892.
Registered office:
Stokes Hall Lodge,
Burnham Rd,
Althorne,
Chelmsford,
Essex,
CM3 6DT,
United Kingdom