On 10/29/15 5:00 PM, Wayne Kline wrote:
Fellow TT'ers
I bought a VNA type antenna analyzer . Just scratching the surface to it'
s capabilities. One thing I know I need to build a set OSL Open Short Load
termination calibrator fittings. Spent some time on Google SMA homebrew
are easy to find... ( f I had bought a SARK 100 which has an SMA connector I
would be golden ) But I need info for an UHF or N connector .
Not wanting to reinvent the wheel anybody have info on such animals ?
Are you looking to homebrew?
Or buy something already made?
Anritsu, for instance, has a OSL 3-in-one
http://configure.us.anritsu.com/catalog/itemView.jsp?siId=OSLN50-1
but at $525, it's probably as expensive as your new VNA.
I don't know that I've ever seen a UHF PL-259/SO-239 cal set.
If you're just going to be doing it at HF frequencies, then you can
probably cobble up a short or open pretty easily with an appropriate
gender connector. A small metal disc works nicely. for the open, the
usual practice is to make sure that the center conductor ends, and the
opening for the shield is completely blocked off.
If you have some N terminations, you could probably modify them to
remove the 50 ohm resistor and replace it with a short or nothing.
Ultimately, if you're interested in precise measurements, you'd need to
know the distance from the connector mating plane to the
open/short/load, but at HF, with a connector that is an inch long, I
doubt the correction is significant.
Or, if you know someone who has a good VNA that's in cal, you could
measure your homebrew units.
There are also schemes to use stacks of adapters.. Cal with your SMA cal
set, then get two SMA:N adapters that can mate. Mate them, measure the
distance through the adapters. Now you know the sum of the two adapters.
If you have all the various genders, you can measure a lot of different
pairs, and do the three cornered (or 10 cornered) hat thing. It's
basically a solving sets of linear equations kind of thing.
Measurement 1 = A+B
Measurement 2 = B+C
Measurement 3 = A+C
So M1+M2 = A+2B+C
M1+M2- M3 = 2B, so now you know B
If you do it in complex coordinates, it's multiplying
M1 = A*B
M2 = B*C
M3 = A*C
so M1*M3/M2 = A*A
I'd not worry about the 0.36 degree phase shift from a 1cm error at 30 MHz.
and so forth.
You could also rig up a sliding short or sliding load, and do that style
calibration.
What's really nice is if you get a few relays, you can build a little
switch box that can do all the shorts/opens/loads. You find someone who
has a VNA to measure your switch box, and now you've got an electronic
cal set.
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