Stereo Tool

If it supports 192 kHz, then usually yes. I can't tell if this always works, but we have never had an issue connecting Spdif to AES/EBU, which your transmitter probably expects. Note that the transmitter also needs to support 192 kHz digital MPX input, left/right won't work.

None, the recommended length for mpx signals with rg58 is 1.80 m , for rg59 less than 3m , beyond these lengths you will have a strong loss of separation.

Orban 8100 manual

Composite ( Baseband) Output
Source Impedance: 470 ohms, independent of OUTPUT ATTEN setting, unbalanced.
Level: variable 0 to greater than 4V p- p by means of 15- turn OUTPUT ATTEN
control.
Connector: Type BNC held floating over chassis ground to permit interface to
various exciters without need for wideband transformer for ground loop suppression.
RF suppressed.
Recommended Maximum Cable Length: 6ft ( 1.8m) RG-58A/U.


pag.L4

https://worldradiohistory.com/Archive-C ... l-1986.pdf

Nope, graph in 8500 manual tells different story.
RG58 capacity per meter is 100pf/m.
According to graph degradation starts at about 4nf (about 55dB separation). That's more than any commercial receiver can separate @15KHz.
So, 30 meters is fine.
I have one installation with 17m RG58 and the separation is above 45dB (this is maximum ability of the Studer tuner to separate the channels).