Batboard

Not too long ago I upgraded the firmware and DSP in my VHF 5K.

I haven't used the radio much since I did it. Pretty much not at all.

But lately I've been using it a lot on 2 meters as I'm in a new car and have not yet installed a mobile radio in it, which will
be a bit of a challenge as Cadillac didn't exactly make the CTS with two way radio installations in mind. I will have to be creative.

Anyway, I'm listening in and I'm hearing something different about the audio quality. Frankly it's pretty bad compared to what it
used to be. Low level sounds like the repeater's courtesy beep, or the CW ID, are weak, fuzzy, and indistinct sounding, while fully
modulated audio sounds like it's overdriving. I can easily tell whose radio has a good limiter on their mic audio, and whose radios
don't have that.

I'm about to upgrade the DSP yet again in hopes this clears the issue. If one is available.
I'm running DSP version 17.00.05 now.

Has anyone else noticed any reduction in audio quality with any particular DSP revisions?

I tend to think it's NOT a problem with the radio itself. I really think it's all about the DSP.


Elroy

Sounds like the tuning parameters may have been wiped. Maybe time for a tuneup?

I had 2 XTL5000's in my CTS, trunk mounted with O3 heads in cockpit. Worked great and there was plenty of room.

Marshall

it sounds like it may be set to narrow band.

current HOST and DSP is R19.50.00 posted April 13 2013 on MOL.

Sounds like it is off frequency instead of a DSP issue.

Interesting....

I have the answer.

The channels being listened to are 2 meter amateur channels. Hams are not required to go to narrowband.

The personality those channels were assigned to had HearClear enabled. (Compander on.) I don't recall that I actually had set that parameter previously. Maybe I did, but I don't remember doing it.

HearClear would work out fine if I'd been listening to true narrowband transmissions.

When I turned off the feature, audio quality was restored.

Apparently, attempting to expand an already wideband signal induces distortion....which should come as no surprise.

But the funny thing is, I never messed with that setting.

It makes me wonder if HearClear was even a working feature in previous firmware/DSP versions. It was clickable, but did it actually work in version 12 firmware on a VHF radio set to 25 KHz channel spacing?

Not being able to restore the radio to the earlier version 12 firmware, I can't actually test that.

It's possible that the feature just didn't work with the older firmware but does work with newer firmware.

If so, shouldn't it be mentioned in the changelogs that accompany each new firmware/dsp release?

If anyone has those changelogs saved and wants to review them and post your findings about any changes to HearClear operation, it could be rather enlightening.


Interesting sidenote: As part of my investigation I bench tested the radio in question and spec'ed out all its important RX and TX parameters. Reference to recently calibrated and certified
test equipment, the receiver, in carrier squelch mode, unmutes at an astonishing -131 dBm, or just .06 microvolts, on a dead carrier. It takes a little more signal (-126 dBm) to unmute on a 2.5 KHz
modulated 1 KHz tone. This is phenomenal sensitivity. It's the best I've EVER measured out of a portable radio. The transmitter is dead stable at 5.88 watts and I know it'll tune up past 8 if I want to do so,
but of course there's no real sense in doing that.

I've had the APX 7000 and the APX 6000 already. Very impressive radios though they are, they didn't match the 5K for receiver sensitivity.


Elroy