Dave,
I am also not aware of any UHF calibration standards. I used the HP cal
kit which is an offset (both open and short) cal kit with the open also
having a fringing capacitance. The VNA removes the cal standards
anomalies during calibration giving a reference plane at the edge of the
3.5mm connector. I think the offset is as you mentioned 32-33ps. I
have hundreds of the RG-142 jumpers which came from some UHF aircraft
diplexers and are manufactured from the same batch of RG-142B. I did
the cal with one of these cables and then cut the connector off one and
soldered the PL-259 on. I was only interested in SWR so losing the
reference plane was not important and could still measure SWR.
I came into a buy of a large number of very high quality new adapters a
year or so ago from a company who designed PCS type cell equipment and
was closing a design center. The BNC to SMA adapters were doubled up
and showed SWR @ 500MHz below 1.05:1. I believe what I did to be
accurate at 500MHz.
Larry, W0QE
On 11/13/2013 5:08 PM, David Kirkby wrote:
On 13 November 2013 22:45, Larry Benko <xxw0qe@comcast.net> wrote:
I had made some UHF connector measurements recently and this discussion
encouraged me to publish them.
If interested see
http://www.w0qe.com/Technical_Topics/uhf_connector_compensation.html
73,
Larry, W0QE
Larry,
I'm not a fan of UHF connectors, but your article was interesting, but
there are a few things I don't understand.
1) You don't describe how you calibrated the VNA which is not so easy
with PL259 as I'm not aware of any cal kits!
It looks to me like you have the open, short and load from an Agilent
85033E 3.5 mm cal kit in the picture, with BNC adapters on them. But
if they are present when the calibration of the VNA is performed, the
error correction will not be correct, as the offset delays of all the
standards will be increased dramatically.
>From memory the offset delays of the opens and short in that kit are
around the 30 to 32 ps, but your adapters will probably add double
that, so all the error correction wil be wrong.
2) Assuming you got a valid calibration, again there is no mention of
the effect of the BNC to SMA adapters. But if the calibration is not
valid, it changes things a lot.
Dave
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