Budget Linked Repeater Network

[BSUFanatic]

What design can enable me to get 2 repeaters to talk to each other when the repeaters have identical Tx and Rx?


Requirements: All radios on this system use the same Tx and Rx
All repeaters on this system must communicate with these radios


This would be a repeater network based upon the repeater design shown in this video (2 hand held radios):

https://www.youtube.com/watch?v=VMkULsNU2_A

I've attached a picture to this post that illustrates the issue I want to solve.


I need Radio 1 to be able to communicate w/ Radio 3

 

[methusaleh]

Well, what are your obstacles, both literally and figuratively? Is topography the main concern? Are both repeaters at elevated locations, as your illustration appears to suggest?

Sounds like a relatively simple "voting" system, however presumably constrained by budget.

 

[slicerwizard]

What design can enable me to get 2 repeaters to talk to each other when the repeaters have identical Tx and Rx?

A design that links the repeaters via an RF link or through the Internet. And uses appropriate controllers.

This would be a repeater network based upon the repeater design shown in this video (2 hand held radios)

No, it wouldn't. Those radios have 300 MHz of TX/RX separation, while your proposed solution has a mere 600 kHz of separation.

I need Radio 1 to be able to communicate w/ Radio 3

Not happening within the parameters you're setting.

 

[n5ims]

A couple of things could work.

First off, using a real repeater instead of two handhelds forced to work as a repeater, should provide better range so only a single repeater might do the trick. It would typically have better antennas, higher power, and less interference from the transmitter part and the receiver part of the repeater. The antennas would also be installed where they will have additional height vs. the two handheld radios could ever think about being installed.

Second, two repeaters on the same frequency pair would need to be separated by enough distance so they don't interfere with each other. This is a two edge sword though. This distance will make it so users on one won't generally be able to talk through the other but if the two are linked you can get additional range since users that are on either one can communicate with users on the other as well as their own.

One comment is that it may be easier if the two repeaters are on different frequency pairs (although this would violate one of your "requirements") since that would generally eliminate the interference issue between the two. That shouldn't be an issue for the users since they would only communicate with the repeater in their area and being on different frequencies would have no affect on their ability to communicate with each other.

A common solution would be to use something like IRLP (IRLP - Internet Radio Linking Project) to link your two repeaters. This would require them to have the associated IRLP hardware on each end as well as an internet connection on each end to allow the link to be established. Check out the "How it works" link on that site for specifics. Depending on your specific configuration, you can link several repeaters together for coverage over several different areas. This technology is used to allow global networks of repeaters to link together for international conferences with literally hundreds of repeaters in multiple countries to take part. Some are on VHF, some are on UHF, but that doesn't matter since IRLP handles everything needed to allow them to communicate as if they were a single repeater.

You could also add one (or more) receivers to each repeater in various areas with a single very powerful transmitter to allow low power handheld radios to be heard from those various areas while each can hear the single transmitter. At the main repeater site, a "voting" controller would select the receiver with the strongest signal and repeat that over the transmitter. This is a fairly complex setup and each individual receiver needs their own link to the voting controller. Also those receivers will need to be designed for this use since they not only would need to relay the received audio, but also the strength of the received signal to that controller.

 

[Project25_MASTR]

A couple of things could work.

First off, using a real repeater instead of two handhelds forced to work as a repeater, should provide better range so only a single repeater might do the trick. It would typically have better antennas, higher power, and less interference from the transmitter part and the receiver part of the repeater. The antennas would also be installed where they will have additional height vs. the two handheld radios could ever think about being installed.

Second, two repeaters on the same frequency pair would need to be separated by enough distance so they don't interfere with each other. This is a two edge sword though. This distance will make it so users on one won't generally be able to talk through the other but if the two are linked you can get additional range since users that are on either one can communicate with users on the other as well as their own.

One comment is that it may be easier if the two repeaters are on different frequency pairs (although this would violate one of your "requirements") since that would generally eliminate the interference issue between the two. That shouldn't be an issue for the users since they would only communicate with the repeater in their area and being on different frequencies would have no affect on their ability to communicate with each other.

A common solution would be to use something like IRLP (IRLP - Internet Radio Linking Project) to link your two repeaters. This would require them to have the associated IRLP hardware on each end as well as an internet connection on each end to allow the link to be established. Check out the "How it works" link on that site for specifics. Depending on your specific configuration, you can link several repeaters together for coverage over several different areas. This technology is used to allow global networks of repeaters to link together for international conferences with literally hundreds of repeaters in multiple countries to take part. Some are on VHF, some are on UHF, but that doesn't matter since IRLP handles everything needed to allow them to communicate as if they were a single repeater.

You could also add one (or more) receivers to each repeater in various areas with a single very powerful transmitter to allow low power handheld radios to be heard from those various areas while each can hear the single transmitter. At the main repeater site, a "voting" controller would select the receiver with the strongest signal and repeat that over the transmitter. This is a fairly complex setup and each individual receiver needs their own link to the voting controller. Also those receivers will need to be designed for this use since they not only would need to relay the received audio, but also the strength of the received signal to that controller.

Does IRLP have remote voting options? I know svxlink and app_rpt both do but I wasn't sure about IRLP.

The problem occurs in the event of possible coverage overlap with the two system (geographical spacing information was not given). If the timing is not right and the two transmitters key up with more than a few milliseconds of difference in passing traffic then the audio will become distorted and possibly unusable to anyone in the overlapping coverage area, The woes and reasons why simulcast analog systems can cost as much as simulcast P25 systems in LMR application…timing is critical. Voting can be done with commonly available software but simulcast is a bit more difficult. Multi-cast however, is not an issue (which throws at least one of the requirements out of the window).

 

[R8000]

Your example shows commercial frequencies being used. If that is the case, you need the help of a experienced radio vendor who has a true RF engineer on staff to design a simulcast system for you (tons of math !). If it is on ham, you are in over your head and can't afford a simulcast system that actually works. If it is a ham system, then remove the line "must be on the same frequency" and just use repeaters on different pairs. You will save yourself tens of thousands of dollars.

 

[BSUFanatic]

Well, what are your obstacles, both literally and figuratively? Is topography the main concern? Are both repeaters at elevated locations, as your illustration appears to suggest?

Mountains and trees are the main obstacles.

Sounds like a relatively simple "voting" system, however presumably constrained by budget.

Keep talking.....how would you set this up?

 

[BSUFanatic]

A design that links the repeaters via an RF link or through the Internet. And uses appropriate controllers.


No, it wouldn't. Those radios have 300 MHz of TX/RX separation, while your proposed solution has a mere 600 kHz of separation.


Not happening within the parameters you're setting.

Thanks for the response. A couple of followup questions.

Could you talk more about this comment? "A design that links the repeaters via an RF link"
Because I don't see anyway to do that.

Also, what's the impact of a larger offset?

 

[BSUFanatic]

A couple of things could work.

First off, using a real repeater instead of two handhelds forced to work as a repeater, should provide better range so only a single repeater might do the trick. It would typically have better antennas, higher power, and less interference from the transmitter part and the receiver part of the repeater. The antennas would also be installed where they will have additional height vs. the two handheld radios could ever think about being installed.

Second, two repeaters on the same frequency pair would need to be separated by enough distance so they don't interfere with each other. This is a two edge sword though. This distance will make it so users on one won't generally be able to talk through the other but if the two are linked you can get additional range since users that are on either one can communicate with users on the other as well as their own.

One comment is that it may be easier if the two repeaters are on different frequency pairs (although this would violate one of your "requirements") since that would generally eliminate the interference issue between the two. That shouldn't be an issue for the users since they would only communicate with the repeater in their area and being on different frequencies would have no affect on their ability to communicate with each other.

A common solution would be to use something like IRLP (IRLP - Internet Radio Linking Project) to link your two repeaters. This would require them to have the associated IRLP hardware on each end as well as an internet connection on each end to allow the link to be established. Check out the "How it works" link on that site for specifics. Depending on your specific configuration, you can link several repeaters together for coverage over several different areas. This technology is used to allow global networks of repeaters to link together for international conferences with literally hundreds of repeaters in multiple countries to take part. Some are on VHF, some are on UHF, but that doesn't matter since IRLP handles everything needed to allow them to communicate as if they were a single repeater.

You could also add one (or more) receivers to each repeater in various areas with a single very powerful transmitter to allow low power handheld radios to be heard from those various areas while each can hear the single transmitter. At the main repeater site, a "voting" controller would select the receiver with the strongest signal and repeat that over the transmitter. This is a fairly complex setup and each individual receiver needs their own link to the voting controller. Also those receivers will need to be designed for this use since they not only would need to relay the received audio, but also the strength of the received signal to that controller.

Thanks for taking the time to write this.

If I had 2 briefcases like in the video both on the same Tx and Rx and were near each other? I figured they wouldn't see each other.