Thanks gents for the help so far, looks like a common problem.
I think I'd like to look at one that detects the effects and artifacts of speech and includes timing, which is what Mike is describing in the AMPX articles he wrote.
The reason for this extra need is that the mobile environment has greatly varying levels and types of background noise:
* City: leaky/corona arcing power lines.
* Highway: passing vehicles' electronic engine control systems making weird pulsating trash out to 30MHz+,
* Anywhere: my own vehicle's ignition noise which is greater or less depending on throttle position (cylinder pressure at firing), etc.. I don't want to fiddle with a computer-controlled vehicle's ignition that's for sure.
* Few or maybe just one place on a car/light truck to mount an antenna or two - newer vehicles are very thin-skinned.
* Vehicles in general have a lot of ambient acoustic noise so adding to it by keeping the squelch open andf the volume high enough is very tiring. X2 for a van vs. car.
Such mobile-related noise, to my understanding and apparently as shown by the S meter, has a large effect on AGC voltage regardless of noise blankers and other noise blanking and noise limiting schemes, which would make it necessary to manually change the bias on a carrier operated squelching device while driving, which is what I want to minimize. On cheap radios it is done with the (carrier based) squelch control. So I am riding the squelch as it is now, or just setting it almost all the way up, which causes me to miss transmissions when the signal is getting weak.
This happens both on ham and CB radio, CB being the worst because of the cheap receiver, but also the CB is likely to be the guinea pig because t it has room inside and if I destroy it, only $45 is lost, compared against the Alinco DX-70 or IC702.
DMOD circuit is interesting but I have not understood it enough to know if the squelch floats with the AGC voltage or acts on audio.
Also, while I am not too offended by SSB while mobile, the idea of keeping squelch closed during carrierless signals is attractive. I am not put off by transistors or ICs at all in a mobile situation, we must all make sacrifices
.