I'm talking about polyethylene dielectric cable. It has velocity
coefficient of 0.659. Its temperature coefficient is negligible.
If you cant identify polyethylene in the cable you are purchasing, then
that's not my problem.
A
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On Fri, 27 Sep 2019, 23:01 , <qrp.ddc@...> wrote:
On Sat, Sep 28, 2019 at 12:09 AM, Alan Lloyd wrote:
I think polyethylene dielectric coax has a pretty reliable velocity
factor of
0. 66.
No, it depends on environment temperature and used frequency.
Also, different cables uses different dielectric and VF may be
significantly different.
For example:
- PE: solid polyethylene, VF=0.659
- PTFE: solid polytetrafluoroethylene, VF=0.695
- ST: solid teflon, VF=0.694
- FE: foam polyethylene, VF=0.79 - 0.88
- FS: foam polystyrene, VF=0.91,
- etc.
I got several cables from aliexpress, some of them doesn't have marking,
but these which have marking has different VF than claimed in
specification. Some RG58 cable from aliexpress have large deviation for VF
and Z.
So, there is no way to identify dielectric with no special equipment. And
there is no way to 100% know exact VF of the cable, even if it has marking.
