No. The 500 does not have a discriminator output as standard. You would have to open it up and do the modification yourself. The PSR800, on the other hand, as I understand it, does have the capability to send true discriminator audio directly to the headphone jack though I have no experience with that model. GRE incorrectly labels this as a "IF output" rather than as a "discriminator" output as I recall. Also, confusingly, the "IF" in the label for the "PC/IF" port of both models stands for "interface" as in "PC (I)nter(F)ace" which is for the computer control of the units as well as outputting processed digital bitstreams for trunking control channel data from EDACS, Motorola, and P25 trunking control channel decoded data.
People understandably get these confused all of the time. In my mind, GRE has done a poor job of labeling and clarifying the use of these ports to the less technically inclined user.
In a nutshell:
PSR500
-----------
PC/IF port = PC interface aka computer control interface also capable of outputting processed digital data which results from the demodulation of some trunking schemes (Motorola, EDACS, and P25). This has nothing to do with either a discriminator output or a separate output for the receiver's final intermediate frequency (IF) section.
There is no stock discriminator output available on this model therefore requiring internal modification to allow that capability if the user desires.
PSR800
-----------
PC/IF port is same as above, however, the unit also has the ability to send discriminator raw audio (as far as I know - with no processing) to the headphone jack thus requiring no internal modification for that capability. This is, or at least used to be incorrectly labeled as "IF Output"; I have no direct experience with this unit and do not know if GRE has changed their nomenclature in newer software/firmware and/or user manuals. The correct label for this would have been "Discriminator Output" which would have been quite clear. A true "IF Output" would tap the output of the final IF BEFORE the discriminator section or any demodulation section.
All I know of the Uniden HP-1 is that it has some kind of data output but I am unclear what its characteristics and limitations are.
-Mike