Farm Communication Link

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Farm Communication Link

Steve Izett

Hi there

Im new to this list

My Son in-law is a farmer with properties some 18km’s apart in Western Australia.

They use UHF CB for general work and safety and one property has zero mobile phone access.

I’m pondering whether i might be able to legally provide an affordable communications solution between the properties.

Could the following be a feasible solution?:

A pair of Ubiquity AirGridM2HP-20dBi providing the 18km IP link (NOT connected to the internet)
A Raspberry Pi running svxlink at each end interfaced to a pair of cheap handheld low power UHF CB handhelds.
All powered by solar batt system.

The aim is a simplex link where any signal that breaks the squelch at one end is retransmitted at the other.
I did a little reading of svxlink wiki and though it has many more available features wondered if it might provide a cheap robust solution?

I’m not a HAM, just have a background in electronics and Comm systems way back in the past and couldn’t find a cheap documented RoIP solution.

I also have next to no linux time.

Hardware sounded OK to me - Pi with USB sound card, PTT provided via interfaced IO port pin.

I would appreciate if this sounds like a reasonable solution if someone might outline the software components to a newbe and how they work.
Could this system be robust enough to function for months without loving care?

Thanks very much.

Steve Izett
Perth Western Australia


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Re: Farm Communication Link

Rob Janssen
Steve Izett wrote:

Hi there

I’m new to this list

My Son in-law is a farmer with properties some 18km’s apart in Western Australia.

They use UHF CB for general work and safety and one property has zero mobile phone access.

I’m pondering whether i might be able to legally provide an affordable communications solution between the properties.

Could the following be a feasible solution?:

A pair of Ubiquity AirGridM2HP-20dBi providing the 18km IP link (NOT connected to the internet)
A Raspberry Pi running svxlink at each end interfaced to a pair of cheap handheld low power UHF CB handhelds.
All powered by solar batt system.

The aim is a simplex link where any signal that breaks the squelch at one end is retransmitted at the other.
I did a little reading of svxlink wiki and though it has many more available features wondered if it might provide a cheap robust solution?

I’m not a HAM, just have a background in electronics and Comm systems way back in the past and couldn’t find a cheap documented RoIP solution.

I also have next to no linux time.

Hardware sounded OK to me - Pi with USB sound card, PTT provided via interfaced IO port pin.

I would appreciate if this sounds like a reasonable solution if someone might outline the software components to a newbe and how they work.
Could this system be robust enough to function for months without loving care?

Thanks very much.

Steve Izett
Perth Western Australia

Hi Steve,

This certainly looks like a feasible system.  I.e. the hardware you propose is certainly able to perform that service.

Whether it is really legal depends on details of the local license conditions for such radios.
There may be limitations to the antennas you can use (e.g. only the portable rubber duck antenna), the connections
you make to the radio (although using the standard mike/headphone connectors is probably allowed, it will likely
be prohibited to make internal connections to the radios.  this is however not strictly required for this purpose),
and it may be disallowed to run such a repeater.  You have to check that in your local regulations.

It should be possible to run a standard "SimplexLogic" and "RemoteTRX" setup connected by IP network over the WiFi link.
Over here we would use 5 GHz (less crowded) but that may not be an issue in such rural areas.
We use the 5 GHz version of those AirGrids for links between our repeaters without issue.

Rob

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Re: Farm Communication Link

Steve Izett
Thanks very much Rob
I’ll check the regs in relation to legality.

I’ll look for  "SimplexLogic" and “RemoteTRX” and see if I cant come up to speed with how these software modules works.

Much appreciated.

Steve





On 19 Jul 2017, at 12:35 am, Rob Janssen <[hidden email]> wrote:

Steve Izett wrote:

Hi there

I’m new to this list

My Son in-law is a farmer with properties some 18km’s apart in Western Australia.

They use UHF CB for general work and safety and one property has zero mobile phone access.

I’m pondering whether i might be able to legally provide an affordable communications solution between the properties.

Could the following be a feasible solution?:

A pair of Ubiquity AirGridM2HP-20dBi providing the 18km IP link (NOT connected to the internet)
A Raspberry Pi running svxlink at each end interfaced to a pair of cheap handheld low power UHF CB handhelds.
All powered by solar batt system.

The aim is a simplex link where any signal that breaks the squelch at one end is retransmitted at the other.
I did a little reading of svxlink wiki and though it has many more available features wondered if it might provide a cheap robust solution?

I’m not a HAM, just have a background in electronics and Comm systems way back in the past and couldn’t find a cheap documented RoIP solution.

I also have next to no linux time.

Hardware sounded OK to me - Pi with USB sound card, PTT provided via interfaced IO port pin.

I would appreciate if this sounds like a reasonable solution if someone might outline the software components to a newbe and how they work.
Could this system be robust enough to function for months without loving care?

Thanks very much.

Steve Izett
Perth Western Australia

Hi Steve,

This certainly looks like a feasible system.  I.e. the hardware you propose is certainly able to perform that service.

Whether it is really legal depends on details of the local license conditions for such radios.
There may be limitations to the antennas you can use (e.g. only the portable rubber duck antenna), the connections
you make to the radio (although using the standard mike/headphone connectors is probably allowed, it will likely
be prohibited to make internal connections to the radios.  this is however not strictly required for this purpose),
and it may be disallowed to run such a repeater.  You have to check that in your local regulations.

It should be possible to run a standard "SimplexLogic" and "RemoteTRX" setup connected by IP network over the WiFi link.
Over here we would use 5 GHz (less crowded) but that may not be an issue in such rural areas.
We use the 5 GHz version of those AirGrids for links between our repeaters without issue.

Rob
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Re: Farm Communication Link

Rob Janssen
Steve Izett wrote:
Thanks very much Rob
I’ll check the regs in relation to legality.

I’ll look for  "SimplexLogic" and “RemoteTRX” and see if I cant come up to speed with how these software modules works.

Much appreciated.

Steve


Ok, you will need to make one system running "remotetrx" and the other one running "svxlink".
Each of them have a configuration file where you specifiy things like the soundcard name, the address of the remote
(the svxlink side will be connecting the remotetrx side) and lots of settings that determine the actual behaviour of
the system.

You need to define some output pin that controls the transmitter on the radio, there will likely have to be a switching
transistor (perferably a small MOSFET like the BS170, 2N7000 etc) as the interface between the output port level
and the transmitter switch current.  Be careful to check how the transmitter is controlled, that tends to be tricky, not
a separate pin that is pulled to ground as was usual in the old days, but some DC path on a signal also used for
another purpose.  So you may need a series resistor.
There are some example circuits people use with the wellknown Baofeng handies, but it is not clear to me if that is
the class of equipment you are going to use.

Then you need some way to know if there is a received signal.  That is where the "make internal connections" thing
could pop up.  There usually is a LED that lights when the radio is receiving, but that info may not be available on any
existing connector.  If it is, you can link it to an input pin (with appropriate level shifting and protection) and use it in the
software.

You can also run the system in VOX mode, where it keys the transmitter when there is audio.
You keep the radios squelched (so they are silent when nothing is received) and when someone talks the other transmitter
comes on.  However, there could be confusion because the remote transmitter will turn off when someone stops talking
but keeps the talk button pressed, the other side starts talking and now they don't hear eachother anymore.

There will be some training required to establish "operating practice", and conventions in place like saying OVER at
the end of each transmission so it is clear whose turn it is to talk.  However, that problem is present without a repeater
as well, it only becomes a little more pronounced because of the delays involved.

Rob

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Re: Farm Communication Link

Steve Izett
Hi Rob
Thanks for the intro.
I thought the tx would be triggered by vox at the receiver but can see an internal radio squelch indicator would be move effective for the reasons given if I can get to it physically.
I have some little handhelds with external speaker/mic/ptt jacks. I’ll need to check out the ptt signal level.

I had previously been trying to get info on RoIP-102 gateways. But couldn’t find reliable info on them. Thats why I turned to you guys and some Raspberry Pi’s.

Thanks again Rob. I’ll do some further reading before making a decision on whether I want to tackle the project.

Steve




> On 19 Jul 2017, at 5:45 pm, Rob Janssen <[hidden email]> wrote:
>
> Steve Izett wrote:
>> Thanks very much Rob
>> I’ll check the regs in relation to legality.
>>
>> I’ll look for  "SimplexLogic" and “RemoteTRX” and see if I cant come up to speed with how these software modules works.
>>
>> Much appreciated.
>>
>> Steve
>>
>
> Ok, you will need to make one system running "remotetrx" and the other one running "svxlink".
> Each of them have a configuration file where you specifiy things like the soundcard name, the address of the remote
> (the svxlink side will be connecting the remotetrx side) and lots of settings that determine the actual behaviour of
> the system.
>
> You need to define some output pin that controls the transmitter on the radio, there will likely have to be a switching
> transistor (perferably a small MOSFET like the BS170, 2N7000 etc) as the interface between the output port level
> and the transmitter switch current.  Be careful to check how the transmitter is controlled, that tends to be tricky, not
> a separate pin that is pulled to ground as was usual in the old days, but some DC path on a signal also used for
> another purpose.  So you may need a series resistor.
> There are some example circuits people use with the wellknown Baofeng handies, but it is not clear to me if that is
> the class of equipment you are going to use.
>
> Then you need some way to know if there is a received signal.  That is where the "make internal connections" thing
> could pop up.  There usually is a LED that lights when the radio is receiving, but that info may not be available on any
> existing connector.  If it is, you can link it to an input pin (with appropriate level shifting and protection) and use it in the
> software.
>
> You can also run the system in VOX mode, where it keys the transmitter when there is audio.
> You keep the radios squelched (so they are silent when nothing is received) and when someone talks the other transmitter
> comes on.  However, there could be confusion because the remote transmitter will turn off when someone stops talking
> but keeps the talk button pressed, the other side starts talking and now they don't hear eachother anymore.
>
> There will be some training required to establish "operating practice", and conventions in place like saying OVER at
> the end of each transmission so it is clear whose turn it is to talk.  However, that problem is present without a repeater
> as well, it only becomes a little more pronounced because of the delays involved.
>
> Rob
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot_______________________________________________
> Svxlink-devel mailing list
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> https://lists.sourceforge.net/lists/listinfo/svxlink-devel


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