At 11/13/2022 07:48 AM, you wrote:
Bingo! That's one of the sources. Fire Departments used to complain that they could not hear dispatch when near a stoplight.
I am forced to keep my 6-M mobile in tone squelch due to all the noise that can be heard as one drives along. I watch the S-meter go half scale on noise quite often. It would drive me out of the car if radio was in carrier squelch.
I've found that different radios respond differently to high noise levels: some will blow squelch, requiring you to turn up the squelch to the point that once you get away from the noise source, it takes over 10 dB quieting to open it in the relatively noise free environment. A good example of this is in comparing the Yaesu FT-8900 to the TYT TH-9800 on 6 meters. With the Yaesu I do have to use CTCSS squelch all the time, but the TYT's squelch stays shut when set on threshold unless a stray signal actually quiets the RX. Weird that it's the Chinese knock-off radio that behaves properly, but it's true.
I have a Kenwood TK-780 that had this problem so bad I couldn't use it as a mobile radio. I was able to fix it by modifying the noise filter per the attached PDF. Apparently the noise above ~15 kHz is negatively affected by the limiter action in the RX, so putting a limit to the high end response of the noise squelch prevents the changing noise level from affecting it.
Bob NO6B
