Why don't repeater owners use the GMRS repeater pairs for a full duplex?

[WRYF747]

Why do repeater owners in this community never go full duplex and just tone duplex instead? Is it for easy convenience, or laziness, or both? (Not to insult)

I just don't get it, we were granted these extra frequencies (467 MHz) that are interlaced with old FRS, and mirrored to the upper repeater-capable channels, why don't we ever use them?

[Sshannon]

8 minutes ago, WRYF747 said:

Why do repeater owners in this community never go full duplex and just tone duplex instead? Is it for easy convenience, or laziness, or both? (Not to insult)

I just don't get it, we were granted these extra frequencies (467 MHz) that are interlaced with old FRS, and mirrored to the upper repeater-capable channels, why don't we ever use them?

They do.  
If you look at the repeater pages you’ll find that they all receive in the 467 MHz main channels and transmit in full duplex on the corresponding 462 MHz main channels. 
Why do you think that they don’t?
 

[WRYF747]

Because I only see one frequency displayed, so it makes me think that it's not a full duplex.

[Sshannon]

15 minutes ago, WRYF747 said:

Because I only see one frequency displayed, so it makes me think that it's not a full duplex.

No, because the offset is always 5 MHz and most type 95e certified radios have preprogrammed repeater channels, there’s little need to specify both frequencies. 

[WRYF747]

Oh. My bad!

[Sshannon]

No problem!  Merry Christmas!

[WRYF747]

And to you too!

[Lscott]

10 hours ago, Sshannon said:

No, because the offset is always 5 MHz

There is nothing in the rules that requires this, but it's the general practice.

https://www.customsmobile.com/regulations/title47_chapterI-i4_part95_subpartE_section95.1763

A few repeater owners have selected a frequency pair from the 462 and 467 groups that are NOT an exact 5MHz offset. That was done to discourage some users, with fixed programed frequencies in their radios, from accessing the repeater. While that will "tie-up" what amounts to 2 "repeater channels" and may not be well received by other repeater owners it's not illegal under the current GMRS rules.

https://wiki.radioreference.com/index.php/Offset

Same with tones. A few owners have required the use of MDC to access the repeater in an attempt to limit unauthorized access. Most of the common Chinese radios can do CTCSS or DCS but not MDC, thus cutting them off from the use of the repeater. The are a number of the more expensive new/used commercial grade radios do include MDC functionality other than Motorola. See attached example brochures.

https://en.wikipedia.org/wiki/MDC-1200

TK-2360-3360 Brochure.pdf TK-5220_5320 Brochure - 1.pdf NX-1200_1300 Num 1.pdf NX-220_320.pdf

[AdmiralCochrane]

Never thought of that.  

 

Also neglected to understand capacitance load of plain open circuit paired wires until I watched a Youtube by AlphaPhoenix challenging people to predict the action of electron flow in a DC branch circuit with open and closed branches. 

[Lscott]

2 hours ago, AdmiralCochrane said:

Never thought of that.  

 

Also neglected to understand capacitance load of plain open circuit paired wires until I watched a Youtube by AlphaPhoenix challenging people to predict the action of electron flow in a DC branch circuit with open and closed branches. 

What you learn quickly the real circuit is not what the schematic shows. When you include all the parasitic elements it’s gets a lot more interesting. The higher the frequency or when transient events are important you can’t neglect them.

[WRKC935]

I am wondering how you would seal with receiver at the subscriber level.  If you put a transmitter on the air in the same band as another radio in receive with 30 feet of each other, the transmitter will overload the receive of the other radio and it goes deaf.  GMRS isn't just in the same band, the whole thing is only 175 Khz wide for the repeater channels.  There isn't a UHF duplexer made that will deal with that sort of spacing.  So how would you even think that it was possible?

Full duplex can't exist at those tight channel spacing.  Just not reasonable to build the filtering for it.  Cell and other technologies had Megahertz of channel spacing available to pull it off.  The analog 800 band is 45 Mhz.  The 700 band is 30Mhz, and the 902 ISM band is 27Mhz for ham and I believe it's more for the commercial users.  It's simply not possible to do on GMRS.