Re: Wrong cable... How bad is it?
The solution depends on what problem you're trying to solve. If you need to meet the stringent flatness spec of the SG503, then you need the cable (or equivalent). Dennis has published an excellent analysis comparing off-the-shelf cables with the official Tek cable. To meet Tek's spec, you cannot assume that "50 ohm cable" is 50 ohm cable. Most are 52 ohms, nominally, and not controlled to that value with any precision.toggle quoted messageShow quoted text
The need for the special cable is caused by the SG503's sensing the amplitude at the front panel connector, not at the ultimate point of delivery. As such, any load mismatch will cause some non-unity VSWR and thus, some departure from flatness. Also, cable loss won't be corrected, either, but that's a secondary problem.
If you don't need the factory-level flatness, you can get by with short lengths of regular cable. The degradation in flatness will certainly be measurable, but may be acceptable (again, depending on your use case). Note that the SG503's sensitivity to cable characteristics is shared by virtually every other sig gen on the planet.
The SG504 replaces the need for expensive coax with the need for a special levelling head (which is almost never found accompanying the plug-in -- see the many efforts to homebrew them, such as the nice one by our own David Partridge). The 504 uses a different arrangement where the amplitude is sensed at the point of delivery, rather than at the generator's front panel connector. If you use no (or negligible) additional cable, the amplitude will be controlled to exquisite precision by the levelling/leveling loop.
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford, CA 94305-4070
On 2/8/2021 14:20, G Hopper wrote:
This is an interesting thread since I, like Stephen, have long assumed my