At 10/26/2022 06:54 AM, you wrote:
All my repeaters , regardless of using flat or non flat audio sound like simplex...
I think you're the first one here to state that... and it's true! Whether you pass unde-emphasized audio through the controller, or de-emph & pre-emph, you can get "flat audio" either way. In the latter case the key is to pick your 3 dB breakpoints such that both 6 dB/octave slopes are active across the entire audio band of interest. For pre-emphasis I use an R-C HPF with the 3 dB point set to ~9 kHz, & for de-emphasis an R-C LPF with a 3 dB rolloff around 60 Hz (I used to go down to ~30 Hz but recently discovered some dynamic range issues within the controller when applying that much de-emphasis, so moved it up a bit). The reason for going this route is to avoid having to individually pre-emphasize all the tone generators & speech synthesizers in the controller, which you must do if you're going to keep the RX audio unde-emphasized.
I'm a stickler when it comes to audio...too many years in broadcast engineering I guess lol...it's not hard to do either...but too many don't take the time to do it right..
I've never worked in broadcast, but still appreciate the sound of a well-engineered repeater that has flat audio response from <100 Hz to 5 or 6 kHz.
I've heard commercial repeaters sound like garbage...
One local linked repeater system switched from Mastr IIs to Quantars a few years ago. While I won't quite call the Quantars "garbage", it was certainly a large step backward in audio quality. One positive outcome of the switch was their 2 meter repeater, on a 15 kHz spaced channel with adjacent channels in close physical proximity, now plays nicely with those adjacents despite the short distance. The issue could have been resolved with the Mastr II given proper deviation adjustment & special audio processing, but with the Quantar's stock config the occupied BW is exceptionally narrow so I give that group kudos for making the change in that one case. But the other 440 repeaters are on 20 kHz spaced channels & don't need to be that narrow, especially when audio quality suffers.
and then there's the ham rptrs, using commercial equipment, set to narrow band yet the users are all wide band....ugh ..one KW TKR750 I know of is set to NB because the wideband filter died...easy to replace but the trustee was too lazy and put the rptr in NB mode....that's just stupid
On 2 meters around here sometimes operating the RX in narrow mode is necessary to avoid adjacent channel interference. Foortunately the G filters in the narrow strip aren't quite as narrow as some of the digital back-ended radios like the Motorola XPR when in 11k0 mode. With the latter you absolutely cannot get 5 kHz through that RX when set to 12.5 kHz - even in 25 kHz mode the IF is rather narrow & very unforgiving of off-channel signals. With the TKR I think you can still get close to 5 kHz deviation through without getting considerable distortion. But yeah if the wide IF chain died switching to narrow should be only used to keep the radio on the air until it can be repaired.
Bob NO6B
