> AFAIK, COM ports are indeed virtual, so this is a puzzle to me. I have
> seen other software in the past (some of it mine) that had a limited
> range of port numbering, but that was an artifact of a GUI design. Chirp
> listed (only) the COM ports that were physically present in the system
> (COM1 and COM19), so I'm not inclined to think that Chirp was at fault
> here; I think it's Windows weirdness. To paraphrase an earlier
> commenter, "Welcome to the world of high-quality Redmond operating systems."

COM19 is perfectly valid, as is COM256.

> Here's an interesting bit of additional information on the PTT question:
> If I open the COM port using PuTTY (terminal emulator), then power on
> the radio with the plug inserted, the PTT does NOT key up. If I then
> close the PuTTY session, the PTT keys up a few seconds afterward. The
> trusty DVM indicates that the TX data line to the radio is held at 0V
> both before and after the PuTTY session, and is high during the PuTTY
> session (except when I'm sending serial data). When I run Chirp, the PTT
> keying only happens before the upload or download starts, and resumes a
> few seconds after it ends.
>
> This suggests that I'm not seeing a bad adapter or cable, but that one
> or both of the following two things is happening: 1) The much-despised
> Prolific chip (the real thing, as far as I can tell, or else they did a
> great job forging the logo and marking) is setting the TXD line to a
> break state when there's no port session in progress, and/or 2) the
> Windows 7 64-bit Prolific com adapter driver (version 3.4.62.293) is
> commanding the adapter's TXD line to a break state when there's no
> session in progress.

This is pretty much par for the course with these radios. It tends to be
DTR leakage into the PTT circuit, which means regular serial signaling
will occasionally cause the radio to transmit. This is, after all, a $20
device you paid $40 for...

> I'll try this out on a 32-bit Win7 system using the canonical Prolific
> driver version, and see if the break-state shenanigans still happen there.

If I were you, I would not waste my time and set the radio to something
it can't transmit on before you go into clone mode.

--Dan


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