Cable Loss without cable

[oh3uu]

Hei

Please tell me what is “Short/Open Circuit: Cable Loss” meaning.

Connecting 75 ohm dummy load into connector of AIM 4170 and doing a scan with Zo 75 ohm from 1 to 30 MHz,
I’ll get all R, X and SWR lines straight like them should be but this “Cable Loss” value varies from 18 db to 23 db.

If I’ll use abt. 5 meters long 75 ohm coaxial cable with “Custom Call” I’ll get this “Cable Loss” variation abt. 18 – 30 db.

Risto

[Bob]

Hi Risto,

The cable loss parameter is valid only when the cable is open or shorted at the far end. In that case it will be a small number.

If the cable is terminated (or partially terminated) with a resistance, the loss will appear to go up since less of the test signal is reflected at the end of the cable.

In the case of a cable without loss, all the test signal is reflected at the open or short circuit at the far end, it all comes back to the rf port and it appears there is not loss in the cable, so the measured loss is zero db.

-- Bob