Help Corbet pick a new mobile HAM

[DaveInDenver]

alright, in 30 words or less... can someone explain the difference between full duplex, and dual channel/dual monitoring? ok 100 words. but that's it

ChatGPT (66 words)

Full duplex: transmit and receive simultaneously on different frequencies—like a phone call. You can talk and hear at the same time. Often used in repeater links or satellites.

Dual monitoring (dual watch/dual channel): the radio listens to two frequencies but has one receiver. It rapidly switches between them and stops when it detects activity. You can’t truly hear both at once, and when you transmit, you’re only on one channel.

Key difference: full duplex = simultaneous TX/RX; dual monitoring = alternating RX only, single TX.

It didn't define channel. You can be single or dual channel with dual watch/monitor but you have to have two channels to be full duplex.

A communication channel is like a highway lane. The combination of a medium (RF, wire, fiber optic, etc), carrier and modulation that facilitates information exchange.

Full duplex has to have two channels, one RX and one TX.

Dual channel has two distinct sets of hardware that TX on two channels, RX on two channels or TX and RX simultaneously.

Watch and monitor are marketing terms as much as engineering.

Dual watch typically uses one set of hardware with a processor that can jump back and forth very fast so you can RX two channels nearly but not actually simultaneously.

Dual monitor typically means the radio is dual channel and can listen to both simultaneously.

(blew past at 139 words, 812 characters)

Extra material

A plain old telephone system call is full duplex because it has two mediums (two sets of twisted pair wires). A ham repeater is full duplex because it uses two carrier frequencies on the same medium of RF. Cell phones are full duplex because they use multiple (complex) modulation on the same medium and carrier frequency.

(56 words, 324 characters)

https://en.wikipedia.org/wiki/Communication_channel

https://en.wikipedia.org/wiki/Duplex_(telecommunications)

https://en.wikipedia.org/wiki/Repeater

 

[Romer]

for our application

APRS on one channel while chatting on another at the same time is Full Duplex

14 words

 

[DaveInDenver]

Talking voice locally is simplex. You TX and RX on the same channel, so can't be simultaneously if you want information actually exchanged.

APRS is simplex as the radio is TX and RX on the same frequency. APRS digipeaters are time-division simplex operating as store-and-forward repeaters. This is networking question where you're defining the physical layer.

When you talk on a repeater you're operating half duplex, you use two channels but can't be simultaneously. You either RX or TX.

The repeater itself is full duplex since it's RX and TX at the same time. That's why there has to be an offset carrier frequency.

RX APRS and TX on another channel is dual simplex not full duplex. Different information is being exchanged on the two channels.

I know you know this Ken and I know being pedantic pisses people off. Mentally I can't unsee/unthink something and I strongly suggest use of the ignore function on my username to limit the audience or ask the club to delete/lock this account.

 

[nakman]

Wow, great stuff! learned something today, thanks guys. sorry @Corbet for the derail...

 

[Romer]

No worries @DaveInDenver. Your explanation is correct. I was over simplifying it

 

[Corbet]

This was a fully acceptable derail and I welcome more like it.

 

[nakman]

the older I get the more I've become "dual watch," at best.. with a fair amount of latency. when I was younger I would have said I was dual monitor. Like if we're listening to a podcast and then you start talking to me, I literally can't hear either one. Same as when the wife asks me a question while we're watching tv. I literally have to mute the tv to focus. anyone else like that? I swear it didn't used to be like this..

 

[RDub]

I’m like that! But part of it is mild hearing damage from years of loud race cars and way too loud music. When too many sounds come at me at once I have a very hard time discriminating anything.

 

[Corbet]

Yup, same.

 

[nakman]

also why I'm pretty content with likes of the FT-8800