> 2) At HF, and at low VHF, mating UHF connectors are nothing more than a
> discontinuity in the impedance of a line that is too small to matter.
That's probably true for most operating. When connectors are used for
calibration purposes, even the smallest discontinuity changes or QC variance
can show up. For example, when conducting OSL calibration on a VNA, I
noticed that when sweeping a calibrating load connector from 1-60 MHz,
return loss was all over the place. The load manufacturer used an Asian
import but the VNA uses silver Amphenol BNCs. Tap the connector and
get -60 dB return loss. Lightly tap on the connector again and I would see
perhaps -25 dB. Granted -25 dB of return loss is an SWR of only 1.12:1,
but a VNA return loss sweep is where you can separate out real connectors
like Amphenol from the brand "X" Asian imports. It may not mean much in a
QSO, but it tells me something about build quality. Under normal operating
conditions, you likely wouldn't notice a whopping 35 dB return loss change
from -25dB to -60 dB unless the connector was used as part of a balanced
bridge or phasing network.
I then made my own my own OSL load using a male Amphenol connector and a
precision 0.1% 50-ohm SMD resistor (not the common 49.9 value for 1%
tolerance) . That one microscopic resistor was a couple dollars from
Mouser! But, it fit perfectly between the center pin and shell. Result?
Consistent -60 dB return loss with excellent repeatability. So, I'm a
believer in the better connectors for calibration needs although I almost
certainly won't see a change in operating performance during a QSO.
Paul, W9AC
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