Specifications

3.3.2 User-fabricated test cables
Using cables other than those supplied by Agilent is not recommended. The cable compensation
function of the instrument may not work properly in non-Agilent cables. If there is an unavoidable
need to use non-Agilent cables, then employ the cable equivalent to Agilent test cables. The Agilent
part number of the cable used for frequencies below 30 MHz is 8121-1218 (not applicable to the
4294A.) Electrical specifications for these cables are provided in Figure 3-11. Do not use test cables
other than Agilent-supplied cables for higher frequencies.
To extend the cables using the 4TP configuration, the cable length should be adapted to the instru-
ment’s cable length correction function (1 m, 2 m, or other selectable cable length.) An error in the
cable length will cause additional measurement error. A detailed discussion on the cable extension
is provided in Section 3.3.3 and in Section 4.
Figure 3-11. Specifications of recommended cable (Agilent part number 8121-1218)
3.3.3 Test cable extension
If the required test cable is longer than 1, 2, or 4 m, it is possible to extend the Agilent-supplied test
cable by using the following techniques.
4TP-4TP extension
As shown in Figure 3-12 (a), all the outer shielding conductors are interconnected at far ends of the
extension cables. Actual connection can be made using four BNC (f) to BNC (f) adapters (Agilent
part number 1250-0080 x 4) as illustrated in Figure 3-12 (b). It is recommended that the BNC
adapters be held in place with an insulation plate to keep the adapters isolated (so as to not break
the 4TP configuration.)
Note: If a conductive plate is used to hold the BNC adapters (without inserting insulators between
the BNC adapters and the plate), the 4TP configuration is terminated at the plate and the
return current does not flow through the extension cables.
3-11