oh4va wrote: ↑Fri Apr 10, 2020 8:28 am
VK3KYY wrote: ↑Fri Apr 10, 2020 8:22 am
I'll try to find an alternative fix for this bug
Roger, that's great.
BTW: Any idea what may cause whirr in the receive audio while listening a FM channel? It is not a local interference. Two more GD77 radios are on the way. When they arrive here in Mikkeli I have a chance compare these radios.
Regards Veijo
The bug appears to be that if CTCSS is assigned to a channel and the Rx detects a tone, it will always turn on the audio amp, even if the signal strength is below the squelch threshold.
In trx.c
See line 404 in trx.c
Code: Select all
if(((!rxCTCSSactive) && (trxRxNoise < squelch)) || ((rxCTCSSactive) && (trxCheckCTCSSFlag())))
{
GPIO_PinWrite(GPIO_RX_audio_mux, Pin_RX_audio_mux, 1);// Set the audio path to AT1846 -> audio amp.
enableAudioAmp(AUDIO_AMP_MODE_RF);
}
trxCheckCTCSSFlag() reads address 0x1C from the AT1846, and in the programming manual data sheet (See the docs/data_sheets ), bit 8 is
ctcss2 compared result
I think what is possibly happening is that the AT1846 is miss interpreting noise as a CTCSS tone and hence enabling the audio amp, and also setting the audio path mux to connect the AT1846S to the amplifier
The output audio from the AT1846S is not muted by the AT1846, so this will result in either hiss or probably a small amount of QRM signal, being output to the speaker
Looking at the original bug. I'm not sure it really is a bug.
Colin's description of the problem is
The problem is that if you remove the tone whilst still transmitting the squelch does not close. Not something that is easily done on most radios but a custom repeater like that described might continue to radiate carrier and just turn off the tone.
It can be demonstrated by receiving a signal with CTCSS and reducing the squelch level to minimum whilst receiving. When the signal is removed the squelch remains open.
(Probably a linked bug is if you open the squelch on a CTCSS channel so the green light is on a signal containing CTCSS will not be received)
I don't know of any systems which remove the tone in the middle of the transmission. I can't easily replicate this without writing some special code in the OpenGD77 to turn of the tone in the middle of the transmission.
I think perhaps if you open the squelch that even if there is a CTCSS applied to the channel (or VFO) that you should hear hiss or a signal (whatever is on that frequency)
I find it strange that I can open the squelch and the green LED comes on, but because I have CTCSS set on a channel that I don't hear anything.
Anyway, I'll take another look at the code...
