Half Duplex

[GMRSNetwork]

Question for any rule experts: We all know that simplex on the repeater inputs is forbidden. What about half-duplex where the base TX is on 462 and RX is on 467 same as a repeater less repeat. Mobiles are reversed. Could not find a rule against it. Same operation as old Taxi systems were mobiles could not talk to each other, only to the base. 

[SteveShannon]

7 hours ago, WRUQ758 said:

Question for any rule experts: We all know that simplex on the repeater inputs is forbidden. What about half-duplex where the base TX is on 462 and RX is on 467 same as a repeater less repeat. Mobiles are reversed. Could not find a rule against it. Same operation as old Taxi systems were mobiles could not talk to each other, only to the base. 

The list of what kind of stations may transmit on which channels is documented in 95.1763:

https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-E/section-95.1763

I’m not sure I really understand what you’re proposing, but maybe the following bold text addresses your question:

467 MHz main channels. Only mobile, hand-held portable, control and fixed stations may transmit on these 8 channels. Mobile, hand-held portable and control stations may transmit on these channels only when communicating through a repeater station or making brief test transmissions in accordance with § 95.319(c)
 

[GMRSNetwork]

Steve, more of a curiosity question... Mobiles would transmit on 467 and base on 462, just no repeat function. Seems to me the rule is clear it MUST be a repeater. Just for a farm wanting a base at a high location to talk to mobiles without having to buy a repeater with duplexer. A repeater is a bases that also re-transmits. A commercial repeater has a mic on it which allows "base" station operation in half duplex as well as repeat for mobiles. 

[SteveShannon]

4 hours ago, WRUQ758 said:

Steve, more of a curiosity question... Mobiles would transmit on 467 and base on 462, just no repeat function. Seems to me the rule is clear it MUST be a repeater. Just for a farm wanting a base at a high location to talk to mobiles without having to buy a repeater with duplexer. A repeater is a bases that also re-transmits. A commercial repeater has a mic on it which allows "base" station operation in half duplex as well as repeat for mobiles. 

I don’t see a question in that post, but why not just use simplex and have the mobiles and base transmit and receive simplex on 462?  Getting a high location for your base makes sense, but doesn’t require using a repeater channel. What are you attempting to gain by operating split? 
In the end it’s strictly up to you and your conscience.  I would be amazed if the FCC ever found out.

[gortex2]

In the ocmmercial LMR world this was common for Taxis and Car companies. They didn't want the other cabs or busses knowing where they were grabbing fares and used half duplex. Dispatcher would hear all of them and cars would here dispatch only. Alot of transit today still does this on voice communications. 

But in a farm type scenario I would think farmer a on tractor b would hope farmer b heard him say he was stuck and needed a tug especally if no one was at base. Simplex would be the best option here I would think. We have a repeater on my farm but 99.9% of the comms is radio to radio and not via repeater. About the only time we use repeater is when we go to town to get fuel or parts. 

[nokones]

7 hours ago, WRUQ758 said:

Question for any rule experts: We all know that simplex on the repeater inputs is forbidden. What about half-duplex where the base TX is on 462 and RX is on 467 same as a repeater less repeat. Mobiles are reversed. Could not find a rule against it. Same operation as old Taxi systems were mobiles could not talk to each other, only to the base. 

It would depend on how the FCC interprets the rule regarding the one-way communication on a channel. One-way Communication is prohibited per 95.1731 and 95.1733 and one-way communication is defined in 95.303.

To get around the rule of ony using the main 467 Meg freq only for communication to a repeater station, the Interstitial freqs do not have that restriction because repeaters are not allowed on the Interstitial freqs.

My thoughts are that any communication that is a two-way passing of information on two separate Interstitial freqs just like on a repeater pair of using 462 and 467 main freqs may be a good argument in using a pair of 462 and 467 Meg Interstitial freqs in a half/semi-duplex configuration could be allowed.

[nokones]

9 minutes ago, gortex2 said:

In the ocmmercial LMR world this was common for Taxis and Car companies. They didn't want the other cabs or busses knowing where they were grabbing fares and used half duplex. Dispatcher would hear all of them and cars would here dispatch only. Alot of transit today still does this on voice communications. 

But in a farm type scenario I would think farmer a on tractor b would hope farmer b heard him say he was stuck and needed a tug especally if no one was at base. Simplex would be the best option here I would think. We have a repeater on my farm but 99.9% of the comms is radio to radio and not via repeater. About the only time we use repeater is when we go to town to get fuel or parts. 

It was also and still used in the Public Safety world. I believe the LA Sheriff Department still doesn't repeat the uplink traffic. They do broadcast a series of beeps to signify that when there is mobile traffic and the channel is busy.

Also, the California Highway Patrol did not repeat their semi-duplex channels for many decades.

[WRUU653]

6 hours ago, WRUQ758 said:

Steve, more of a curiosity question... Mobiles would transmit on 467 and base on 462, just no repeat function. Seems to me the rule is clear it MUST be a repeater. Just for a farm wanting a base at a high location to talk to mobiles without having to buy a repeater with duplexer. 

Aside from the rules being what they are you would need to be running duplex on both the mobile and base or they wouldn’t hear each other in this scenario. I don’t see what would be gained by doing this. Just use simplex with a base.

6 hours ago, WRUQ758 said:

. A repeater is a bases that also re-transmits. A commercial repeater has a mic on it which allows "base" station operation in half duplex as well as repeat for mobiles. 

 

A repeater also repeats the mobile signal on the same 462 RX as you would be when using the mic on repeater. It isn’t a one way communication for anyone listening on 462. All communication is heard on the same 462 frequency as it is when going through a repeater.

[SteveShannon]

8 minutes ago, gortex2 said:

In the ocmmercial LMR world this was common for Taxis and Car companies. They didn't want the other cabs or busses knowing where they were grabbing fares and used half duplex. Dispatcher would hear all of them and cars would here dispatch only. Alot of transit today still does this on voice communications. 

The OP could do that by simply using split tones on simplex also. One tone for transmitting from the mobiles and one for the base.

[SteveShannon]

17 minutes ago, nokones said:

My thoughts are that any communication that is a two-way passing of information on two separate Interstitial freqs just like on a repeater pair of using 462 and 467 main freqs may be a good argument in using a pair of 462 and 467 Meg Interstitial freqs in a half/semi-duplex configuration could be allowed.

Except neither base nor mobile units are allowed to transmit on the 467 interstitial channels.

[WRTC928]

1 hour ago, SteveShannon said:

The OP could do that by simply using split tones on simplex also. One tone for transmitting from the mobiles and one for the base.

I was about to say that simplex with split tones would accomplish the same thing. Great minds think alike? 

[Northcutt114]

1 hour ago, SteveShannon said:

Except neither base nor mobile units are allowed to transmit on the 467 interstitial channels.

Repped for appropriate use of "interstitial." 

[nokones]

2 hours ago, SteveShannon said:

Except neither base nor mobile units are allowed to transmit on the 467 interstitial channels.

In the Farm scenario, the farmer in the field would have a portable that would communicate to the Farm Base. There would be no need to install a mobile on a tractor or harvester. 

[Northcutt114]

I've been thinking about this for a bit this morning and I can't quite figure out what the OP is trying to do.

HT's in the field that talk to each other and not step on the base? And then the base can transmit out to all the HT's?

If that's the case, why not just tune into two different 462 channels and have the HT's on dual watch? No need to even bother with the 467 channel. Unless, of course, I'm misunderstanding what the OP wants, which is definitely possible.

 

[SteveShannon]

15 minutes ago, Northcutt114 said:

I've been thinking about this for a bit this morning and I can't quite figure out what the OP is trying to do.

HT's in the field that talk to each other and not step on the base? And then the base can transmit out to all the HT's?

If that's the case, why not just tune into two different 462 channels and have the HT's on dual watch? No need to even bother with the 467 channel. Unless, of course, I'm misunderstanding what the OP wants, which is definitely possible.

 

No, the way he explained, he would have mobiles in the field able to transmit to the base without hearing each other, but when the base transmits all the mobiles would hear it. Unfortunately that will also make it easy for one mobile to step on another. He never mentioned handhelds and since one of his goals is to get the base antenna up high I assume he is hoping to achieve better coverage. For that reason, I think Kenny’s idea of using the interstitial channels, which would require 1/2 watt ERP handheld radios in the trucks, tractors, combines, swathers, etc. wouldn’t be ideal.

[Northcutt114]

6 hours ago, SteveShannon said:

No, the way he explained, he would have mobiles in the field able to transmit to the base without hearing each other, but when the base transmits all the mobiles would hear it. Unfortunately that will also make it easy for one mobile to step on another. He never mentioned handhelds and since one of his goals is to get the base antenna up high I assume he is hoping to achieve better coverage. For that reason, I think Kenny’s idea of using the interstitial channels, which would require 1/2 watt ERP handheld radios in the trucks, tractors, combines, swathers, etc. wouldn’t be ideal.

Gotcha...I guess I just conflate "mobile" with "HT."

I can't figure out what OP is trying to do, so I'll take my unhelpful opinion and vacate. Best of luck! 

[SteveShannon]

1 hour ago, Northcutt114 said:

Gotcha...I guess I just conflate "mobile" with "HT."

I can't figure out what OP is trying to do, so I'll take my unhelpful opinion and vacate. Best of luck! 

Please don’t feel like you’re being chased away. Until the OP comments again we’re all just speculating. 
A handheld is a subset of the FCC designation “Portable” rather than “Mobile” but it can be confusing. 

[Northcutt114]

41 minutes ago, SteveShannon said:

Please don’t feel like you’re being chased away. Until the OP comments again we’re all just speculating. 
A handheld is a subset of the FCC designation “Portable” rather than “Mobile” but it can be confusing. 

Far from it, in terms of being chased away. I just know that there's a lot that I don't know already. "Portable" and "mobile" are still confusing to me. I suppose the operative difference being that portables are not "installable" where as mobiles are. Either way, in for OP's clarification.

 

[SteveShannon]

30 minutes ago, Northcutt114 said:

Far from it, in terms of being chased away. I just know that there's a lot that I don't know already. "Portable" and "mobile" are still confusing to me. I suppose the operative difference being that portables are not "installable" where as mobiles are. Either way, in for OP's clarification.

 

From the regs:

Mobile station. A station, intended to be used while in motion or during halts at unspecified locations, that communicates directly with base stations and other mobile stations, and with control stations and other mobile stations through repeater stations.
 

Hand-held portable unit. A physically small mobile station that can be operated while being held in the operator's hand.

So i said it wrong. A handheld portable is a subset of the mobile category. 

[marcspaz]

For what its worth, per § 95.1763, Fixed Stations can communicate simplex on what are traditionally known as repeater inputs, 467.5500, 467.5750, 467.6000, 467.6250, 467.6500, 467.6750, 467.7000, and 467.7250 MHz. 

Keep in mind, a Fixed Station is defined by it's use, not it's radio type.  A Fixed Station is a station at a fixed location that directly communicates with other fixed stations only. On GMRS, fixed stations are limited to 15w. 

So, as an example, if you have a radio hooked up to an antenna on the roof of your house, and you are talking to someone with a radio setup at there house with an antenna on their roof, you can 100% talk simplex on 467.600 MHz.

[Northcutt114]

14 hours ago, marcspaz said:

Keep in mind, a Fixed Station is defined by it's use, not it's radio type.  A Fixed Station is a station at a fixed location that directly communicates with other fixed stations only. On GMRS, fixed stations are limited to 15w. 

Apologies if this is outside the scope of this thread, but I've always found that to be an almost impossible definition. "...that directly communicates with other fixed stations only" seems to be a really high bar. I have a base station that I would consider to be "fixed." It doesn't move and while it is a "mobile" radio, it is not mobile at all. But the people that I talk to on it are sometimes on a mobile radio in their car, or an HT, or a mobile unit at home. But my, somewhat, fixed station does not communicate with other "fixed" stations only.

So what is a use case where you have two units that only talk to each other and are both non-mobile where you would have to downlimit you TX power? Something like a ranch where you have a base station in the barn and one in the house? And the idea being to keep the TX power down so as not to spill outside of the AO of the two radios?

 

[WRUE951]

17 minutes ago, Northcutt114 said:

Apologies if this is outside the scope of this thread, but I've always found that to be an almost impossible definition. "...that directly communicates with other fixed stations only" seems to be a really high bar. I have a base station that I would consider to be "fixed." It doesn't move and while it is a "mobile" radio, it is not mobile at all. But the people that I talk to on it are sometimes on a mobile radio in their car, or an HT, or a mobile unit at home. But my, somewhat, fixed station does not communicate with other "fixed" stations only.

So what is a use case where you have two units that only talk to each other and are both non-mobile where you would have to downlimit you TX power? Something like a ranch where you have a base station in the barn and one in the house? And the idea being to keep the TX power down so as not to spill outside of the AO of the two radios?

 

Low Power  

[Davichko5650]

For my expert rules interpreters,  What from 47 CFR 95 95.303  waht differentiates the two listed below?

 

Base station. A station at a fixed location that communicates directly with mobile stations and other base stations.

Fixed station. A station at a fixed location that directly communicates with other fixed stations only.

Enhanced Content - Paragraph Tools

URL

https://www.ecfr.gov/current/title-47/part-95#p-95.303(Fixed station)

Citation

47 CFR 95.303  "Base Station" - “Fixed station”

 

If I'm using a mobile rig at a fixed location and talking to my buddy in his truck on his mobile, I'm a base station, but if I'm talking to him on his mobile rig at his house we're both fixed stations? Seems like we flip-flop a ot when involved in a multi operator conversation with our home stations, a mobile and my buddy at the park on his HT ( a very common scenario around here).

Coming in from the amateur world, I was always under the understanding that a fixed station was something like a UHF link to a repeater from a remote receive site or similar...

[KBSherwood]

14 hours ago, marcspaz said:

For what its worth, per § 95.1763, Fixed Stations can communicate simplex on what are traditionally known as repeater inputs, 467.5500, 467.5750, 467.6000, 467.6250, 467.6500, 467.6750, 467.7000, and 467.7250 MHz. 

Keep in mind, a Fixed Station is defined by it's use, not it's radio type.  A Fixed Station is a station at a fixed location that directly communicates with other fixed stations only. On GMRS, fixed stations are limited to 15w. 

So, as an example, if you have a radio hooked up to an antenna on the roof of your house, and you are talking to someone with a radio setup at there house with an antenna on their roof, you can 100% talk simplex on 467.600 MHz.

Learned something new this morning, appreciate it!

[SteveShannon]

48 minutes ago, Northcutt114 said:

Apologies if this is outside the scope of this thread, but I've always found that to be an almost impossible definition. "...that directly communicates with other fixed stations only" seems to be a really high bar. I have a base station that I would consider to be "fixed." It doesn't move and while it is a "mobile" radio, it is not mobile at all. But the people that I talk to on it are sometimes on a mobile radio in their car, or an HT, or a mobile unit at home. But my, somewhat, fixed station does not communicate with other "fixed" stations only.

So what is a use case where you have two units that only talk to each other and are both non-mobile where you would have to downlimit you TX power? Something like a ranch where you have a base station in the barn and one in the house? And the idea being to keep the TX power down so as not to spill outside of the AO of the two radios?

 

Fixed Stations are rare and used for dedicated communications between two or more static locations. As such they simply don’t need more power. They could be used for analog telemetry or intercoms. The only advantage of designating a pair of radios as fixed stations is to be able to use the 467 main channels.