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It all depends on the quality of the adapter. Adapters from high end companies with expensive prices would be very good and 0.1 dB would be close. Unknown low cost brands would be worse and sometimens worse than 0.2 dB.
I spent lot of time to try to measure the loss of "low loss" coax transition.
The answer to your questions is:
1) it depend on frequency.
But are you interested to s21 or the dissipative loss?
SMA are not a precision connector, so s21 (and the other spar) are sensitive to the inductance of the pin retraction. The dissipative loss isn't.
To give the value for a Radiall R127705 gold plated SMA double female , read on VNA and SNA:
@ 1GHz: 0.03 dB
@18GHz: 0.06 dB
The uncertainty bar is mutch larger than the observed value
Hi, sergio mariotti:
I am interested in dissipative loss.
I use common SMA female to female convertor,I mean it has no model and I don't know the producter. It has been used for a long time, more than 2 years.
The freq is about 2GHz.
Which value is more suitable for me?
Hi,marcomdd:
yes, I am interested in noise temp of the SMA, It's not the SMA connector, but SMA female to female convertor.
At 290K, what's its noise figure or noise temperature?
I've now dissussed privately with marcomdd about this question.
Effectively the most formal method to know the noise temperature introduced by an in line 2 port network (sma f-f, in this case) pass trough the knowing of the Available Gain (Gav).
The Dissipative Attenuation defined on "Microwave Attenuation Measurement - Warner - IEE Press" is:
dissipative attenuation=|s21|^2/(1-|s11|^2)
and is an old definition, may be valid if Gammasource=0.
In any case, the spar measurement of a low loss, coax DUT depend strongly on the pin recession of both the the couple of the ports (DUT and VNA).
Often you may assume that the VNA port is completely corrected, but it's not true. The pin of a 3.5mm connector may be recessed from 0 to 3mils.
The error introduced by a 3 mils recessed may be important and erroneously considerated as part of the DUT.
It's difficult for me make such measurement.
I just want to get a typical value of noise temp or available loss of a sma adapter.
I measured the NF of a 10dB attenuator, but there is a sma adapter in front of it. And the room temp is not 290K, it's about 300K.
The measurement value is about 10.4dB.
If available loss of the sma adapter is 0.2dB, I have calculated the true NF of the attenuator is about 10.3380. Very close to my measurement result.
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