'Squelch' Firmware suggestion for x36HP's

[Boatanchor]

Firmware changes/suggestions for x36HP's

I'm not sure if this could be implemented on the new Uniden scanners.
It depends whether the recovered analogue audio is routed through the DSP/CPU for processing.

However, I'm sure that if it could be implemented, it would appeal to many users and would be a definite advantage over competitors models

The suggestion - A "Quiet FM squelch" menu option.

If Uniden could introduce a 100mS or so audio delay into the demodulated FM audio, it would be possible to offer a 'quiet squelch' menu option that would eliminate the squelch crash from ALL FM signals.

This function is often implemented in FM repeaters to eliminate the squelch crash at the end of transmissions. It is simple and very effective.

All you have to do is add a 100mS or so audio delay. The scanners normal tone/noise mute circuit actually closes 100mS or so before the audio delay has completed playback, thus eliminating the squelch crash at the end of transmissions.

Ideally, having the audio delay adjustable between 50mS-200mS would ensure the squelch crash would be eliminated from all FM systems.

The audio delay would have no perceptible impact on scanning performance.

If Uniden doesn't adopt it, maybe someone from Whistler reads this

Anyway, that's just my small contribution to the ongoing discussions..

Happy Scanning

 

[Boatanchor]

Time for another suggestion to improve our listening enjoyment

FM 'Tone/CTCSS filtering'

Now this may not be an issue in the new scanners, but if Uniden is relying on the same crude R/C style bandpass filtering to filter out CTCSS tones as the previous models, its time to change for the better.

Many conventional FM services utilize CTCSS and many of these use the higher CTCSS tones to reduce the decoder times and speed up the tone squelch opening speed (higher tone frequencies = faster tone decoder times = faster mute opening).

The problem is that traditional R/C style, 300Hz-3.5Khz audio bandpass filters don't have a tight enough frequency response to reject the higher CTCSS tones very well. Systems that use >220Hz tones for example, invariably subject listeners to a continuous, annoying low frequency tone behind the voice. This is most noticeable when using good quality headphones or external speakers that respond well to low audio frequencies.

What we need instead is a DSP based high pass audio filter, with a cut off frequency of 300Hz.
Having the DSP HPF activated or deactivated based on the condition of the channel's tone field would
make the process of activation and deactivation of the HPF a simple process.

An alternative method would be to utilize an adaptive DSP based notch filter, which again, could take it's programming cue from the channel's tone field.

I'm monitoring a conventional FM system right now on the 996XT. This system uses a 241Hz tone which drives me nuts because the 996XT audio bandpass filtering virtually lets this tone go through to the speaker/headphones unimpeded

'Real' (commercial/professional) radios do not allow users to hear the CTCSS tones, no matter how high they are.