[Amps] All the recent UHF connector discussion

[Larry Benko]

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 at 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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