[ICOM] Tone squelch operation, "uniformed" question

[D C *Mac* Macdonald]

I believe I must disagree with Dick on this one. 
 
You are speaking of FM mode communications 
here, not AM or SSB. The FM mode exhibits a 
characteristic known as "capture effect" where 
the strongest signal will capture the receiver. 
One of the specifications for an FM receiver is 
the quality of that capture effect, expressed in 
dB. The lower the capture effect rating in dB, 
the smaller the difference in signal strength 
must be for the stronger to capture the receiver. 
This might be as low as 1 dB for a GOOD receiver!
 
Therefore, I would expect the tone of the weaker 
input signal to be greatly suppressed and very 
little of the lower strength signal would be processed. 
 
Even if both signals are using the same tone, the 
stronger signal will "win out" although you may 
hear some scritch AND even a heterodyne if both 
signals are within a few dB in signal strength. 
 
* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* k2gkk at hotmail.com * 
* (Since 30 Nov 53) * 
* Oklahoma City, OK * 
* USAF, Ret (61-81) * 
* * * * * * * * * * * 
 
 
 
  

> Date: Tue, 14 Feb 2012 00:35:33 -0800
> From: dick at k7vc.com
> To: icom at mailman.qth.net
> Subject: Re: [ICOM] Tone squelch operation, "uniformed" question
> 
> Yes. In my experience the two encoded tones will mix and you will hear 
> the audio products (sum/difference) and the stronger of the four RF 
> carriers will capture the others. Depending on the tone filtering and 
> other characteristics of the radios, the tonal grunge can be either 
> minimal or overwhelming. It is one of those things that just has to be 
> tried as there are too many variables to give a definitive answer.
> 
> Is this just an academic question or are you actually trying to create a 
> useful application?
> 
> Dick
> 
> --
> Dick Flanagan K7VC
> dick at k7vc.com
> 
> 
> On 2/13/2012 11:25 PM, George J. Nixon Jr. wrote:
> > Suppose that operators A and B have IC-W32a or equivalent ICOM VHF 
> > capable radios, and are having a QSO with normal settings on a VHF 
> > simplex frequency.
> > Suppose that operators C and D have similar rigs, get on the same VHF 
> > simplex frequency, and set the same subaudible transmit and receive 
> > tones. When operators C and D start a QSO at the same time when A and 
> > B are in their QSO, will they hear (be QRMd) by the QSO of C and D? 
> > 73 - George, N9EJS