A question about extending repeater coverage

[password]

This is just an idea I've had and would like some input in it, mainly concerning legality not practicality. I currently have a repeater on .700 and it got fairly good coverage, about 8 miles on a hand held (130ft db408 with flat land) . I can hear it close to 15 miles out but cant get back into it. It’s also only 7W so I can turn it up a good amount, just haven’t as there’s no point to it.

 

My idea is to have a "repeater" that links into the main repeater for improved handheld coverage, it would be on a simplex pair and repeat onto the repeaters main input channel. This should allow me to hear the repeater directly then use one of the linking repeaters to get into it.

 

The gmrs repeater input channels are just to close in frequency for me to practically use those as a rx and tx in one repeater, as they would only be 0.5~ MHz apart using repeater input frequency’s. The aux repeaters would have PL tones to avoid bubble pack users form getting into the system.

 

The aux repeaters would have an input of 462.500 and output of 467.700 and just extend the main repeaters reception, The output would be yagi back to the main repeater and its 462.500 would be an antenna like a db-404, this would allow hand held coverage in areas you cant currently get into the repeater at.

 

My question is, is such a system legal, or is there something preventing this from being legally doable.

[marcspaz]

The idea/concept you are looking for is an RF-linked mesh network.  Same concept as cell phone service.  It's legal and easy, but expensive.  I have done it for IT wireless networks, but not voice.   There are many clubs and owners who have networks that may be willing to talk to you about it.  Some of them are members of this forum.

 

I would stay far, far away from simplex rebroadcasting devices.  They are more annoying than helpful.  I would put them in the category of "when all else fails, its better than nothing."

[WRAK968]

The aux repeaters would have an input of 462.500 and output of 467.700 and just extend the main repeaters reception,

The main issue I see here is that you could inadvertently cause an unlicensed user using a bubble pack radio to transmit on a repeater without knowing it. Another way of doing it would be to use RoIP which would link two repeaters together over the internet. This is how my system is set up, or was, Just went down due to a PA failure The nice thing is that users are still required to transmit on the 467.xxx frequencies which means the bubble pack radios won't become a nuisance on the repeaters themselves.

[password]

I had considered useing internet basced repeating, but i cant find any good fit for gmrs, What did you use? I also do not have internet at the repeater site, but I could devise a way to get it there.

 

I am conserned about bubble back users but using non-standered tones, I cant see how anyone would ever "find" this for use with bubble pack radios.

 

This is more of an idea for me, I've got countless moble kenwoods on the shelf and could rig up one of these fairly quickly. My main consern is is it legal to use not repeater input frequnacys as repeater inputs?

[quarterwave]

How about another repeater part way into the coverage area you want to expand to, and part way in the existing coverage area. Same Freqs, just use a different PL to get into the second repeater, but same output PL. 

 

Think of it as overlapping circles. 

 

I know of an entire county's fire system that was setup that way years ago, we called it poor mans trunking. 

[password]

The problem with building to is location, I got lucky on my first tower location but it’s unlikely I could get another good location.

 

I can set up these simple repeaters at houses how ever, hence why I liked that idea. I could also link repeaters but I’m yet to see a fairly good way, and I’d need Internet at the tower site.

 

I’m mainly looking for any input on I’d such a system I’m thinking of would be legal or not

[marcspaz]

...My main consern is is it legal...

 

 

It is perfectly legal to create a mesh network and/or use RF or internet linking.  The only problem I see with your original post is, the pairing offsets for duplexing.

 

You have 2 options. 1.) use a simplex repeater which records what it receives and then re-transmits the recording, or 2.) you must use a proper duplex (split mode) frequency pair (462.7250 MHz and 467.7250 MHz, for example).

 

The other 2 things to track is your max transmit power and bandwidth.

[password]

That’s what I’m trying to figure out, I would be using a proper pair on the main repeater but when useing one of the AUX repeaters i would be useing an extra frequency

[Logan5]

Yep, it starts to get real complicated after that. lol, I'm out.

[password]

I dont fell ive properly explaned how this system is designed out.

Here is an image with a bit of an explination, The red line is the repeaters main heatrable range on handhelds, you can get back to the repeatetr and its useable in the green zone. This is a normal 462/467 repeater

 

Inside the yellow zones you would turn to an extended zone, this would be like 462.550 and would just pick up your signal and output it onto the 467.700, so you would be useing a 462.550/462.700 split on your actual handheld.

 

This should work out with what ive played with, its just a question of legality at this point.

[marcspaz]

That’s what I’m trying to figure out, I would be using a proper pair on the main repeater but when useing one of the AUX repeaters i would be useing an extra frequency

 

Don't use an extra frequency.  I'm no lawyer, but I think that violates FCC rules.  Use one pair for all nodes and overlap coverage, use RF linking, or use internet linking.

 

EDIT:  Again, I'm not a lawyer, but as far as I can tell, there is no legal limit on how many approved pairs you can use in an RF linked network.  However, your link pairs should use extremely narrow focused beam directional antennas on the lowest usable power, so you avoid harmful interference.  Otherwise the FCC will shut you down after a handful of complaints.

 

I dont fell ive properly explaned how this system is designed out.

Here is an image with a bit of an explination, The red line is the repeaters main heatrable range on handhelds, you can get back to the repeatetr and its useable in the green zone. This is a normal 462/467 repeater

 

Inside the yellow zones you would turn to an extended zone, this would be like 462.550 and would just pick up your signal and output it onto the 467.700, so you would be useing a 462.550/462.700 split on your actual handheld.

 

This should work out with what ive played with, its just a question of legality at this point.

 

 

That image is a mesh network.  That is why I told you to lookup how mesh networks work, and then apply the principles to your GMRS Network.  Ham clubs and amateur radio repeater owners do this all the time. Especially for regular nets and emergency operations.  The repeaters are all linked via an RF PTP controller or via an internet controller.  Then, when they have their daily/weekly meeting on the radio, regardless of the location, everyone on every repeater can hear each other.

 

Two members here have meshed their systems together using the overlap method.  Its the cheapest and easiest.  However, if you happen to be somewhere that you can hear two or more repeaters at the same time, there is a very slight echo.  Almost not noticeable.  That is the only drawback I am aware of, but together they cover more than 6,000 square miles.

[rdunajewski]

Sounds like you're looking for a voting system where the yellow circles are satellite receivers, and the audio gets back to the transmitter site (which can and should also have its own receiver, like a normal repeater). Then you need something to evaluate the signals coming in from the array receivers and select which one to use as the transmitter's source of audio to repeat. The voter can switch fairly seamlessly between receiver sites as the signal varies during a transmission. Rather than cutting out when the signal changes, ideally a second receiver will pick up the user and the repeater will grab that other receiver's audio.

 

Traditionally this is done with leased phone lines or microwave links which are very expensive. However, this can also be done over the Internet with one major caveat: timing. When your voter is comparing the signal quality of each receiver, the audio waves need to be in-phase (synchronized) for the comparison to work. For RF or copper links, this is pretty simple to do as everything comes in (roughly) at the speed of light. Over the Internet, however, the packets containing the audio can and will be delayed by variable amounts of time. The only way to line up the audio across various receiver sources is to use an accurate timing system like GPS to "timestamp" each packet and assemble them on the other end. 

 

There's a device called an RTCM for Allstar which does this. They're not super cheap but nowhere near the expensive professional grade stuff. You'd need one at the repeater location and one for each additional receiver, plus a GPS for each site. I've done some experimenting with these. You can even achieve simulcast where you have multiple transmitters at the same time, but the RF needs to be in-phase as well or the transmitters will interfere with each other instead of "amplifying" their collective signals. You'd need transmitters which have an external 10 MHz reference signal and a timing source based off GPS ($$) to provide a synchronized 10 MHz clock input. I haven't gone this far, and I think this is probably overkill for GMRS.

[password]

Yes basically a voting system but not voting, each of the yellow marked ones would have a different input, likely determined by PL tones so no two are ever transmitting at once, and there’s no audio to vote with. I get how a normal mesh works, but I’m looking for a more simple system.

 

The yellow ones would not output anything but a link and the main repeater would be the only output

 

My question is on linking frequency’s, after much looking I’m assuming the FCC considers them as fixed usage and it is alloud

[marcspaz]

Yes basically a voting system but not voting, each of the yellow marked ones would have a different input, likely determined by PL tones so no two are ever transmitting at once, and there’s no audio to vote with. I get how a normal mesh works, but I’m looking for a more simple system.

 

The yellow ones would not output anything but a link and the main repeater would be the only output

 

My question is on linking frequency’s, after much looking I’m assuming the FCC considers them as fixed usage and it is alloud

Oh, man... now I get what you are trying to do. That's actually a good idea. I'll have to think about that for a few. I don't see any legal issues... just need to think of the best method. Split PL for sure.

[password]

It’s definitely a different idea, but this repeater was a crazy idea I had one day and now it’s fairly solid, my concern is that I can’t use the repeater input frequency’s as they are just to close for isolation, so I’d have to have an input on 462.550 for instance not 467.550 as that’s just to close to my link frequency back into the main repeater.

 

There will obviously be a pl on this but it still could technically allow an unlicensed user into the system without them technically doing anything illegal. It seems unlikely it would happen but I’m unsure how the fcc looks at this as I’m “allowing” it to happen by using a frequency that’s not exclusive to licensed users but I did protect unlicensed used the best possible way I could.

[Radioguy7268]

I'd look at why your repeater doesn't receive as well as it should.  If it can transmit out with full quieting to 15 miles at just 7 watts, then a 4 watt portable should talk back in from that distance. A good used band pass filter & a receive pre-amp would set you back less than $250. What's your effective receive sensitivity measured at the site? (how strong of a signal does your receiver system require before it opens the repeat audio path?) What's the noise floor? Do you have any desense when the repeater begins to transmit?

 

Your idea of satellite receivers is worthwhile, but you're already seeing that it's limited due to the lack of frequency spacing and spectrum if you stick to GMRS.

[DeoVindice]

I've thought about this myself for a couple different applications.

 

Nonstandard and split QT tones would be one option for barring unlicensed users; it would restrict repeater use to those with OSTs or the ability to program nonstandard tones. I bet you could also use DTMF FleetSync option signalling, with every transmission through the extender SELCALLing the extender such that it would only be usable to users with DTMF or FleetSync. No bubble pack radio I'm aware of can do FleetSync or DTMF.

 

"Upside-down" repeaters could be used, whether permanently or temporarily, to expand repeater coverage into an area to which the repeater lacks line of sight. There are quite a few areas like that in the Mountain West, where a mountain range's shadow blocks RF.

 

It could also be useful when working in deep gulches or hollers, with a portable repeater/extender placed on the spur to facilitate comms into the holler. I've dealt with that sort of situation while doing SAR in the deep Ozarks; we wound up placing a man up high to act as a radio relay since no extenders were available.

 

A high-power extender would also make quite a bit of sense mounted in a vehicle if you anticipated being dismounted with a handheld and line of sight to the vehicle, as you'd be able to leverage the extender's higher power and better antenna to reach out a lot further/with better signal strength.

[password]

I'd look at why your repeater doesn't receive as well as it should.  If it can transmit out with full quieting to 15 miles at just 7 watts, then a 4 watt portable should talk back in from that distance. A good used band pass filter & a receive pre-amp would set you back less than $250. What's your effective receive sensitivity measured at the site? (how strong of a signal does your receiver system require before it opens the repeat audio path?) What's the noise floor? Do you have any desense when the repeater begins to transmit? I

 

Your idea of satellite receivers is worthwhile, but you're already seeing that it's limited due to the lack of frequency spacing and spectrum if you stick to GMRS.

The repeater is reachable in all most all locations, but not on handhelds, and if it is it’s vary unreliable. The desence is higher then I’d like when the repeater is in TX but it’s not really that bad at all compared to simplex. I’ve got a Sinclair q3220e and another can in the RX I can’t remember. But it’s not really about extending range just solidifying the coverage I have.

[deanq]

What antenna system does the repeater have? A better antenna would be cheaper or possibly a receive amplifier. Or both.

[password]

The antenna is a DB-408 (factory set for GMRS), with about 80FT of LDF-50 coax on it

[Radioguy7268]

The repeater is reachable in all most all locations, but not on handhelds, and if it is it’s vary unreliable. The desence is higher then I’d like when the repeater is in TX but it’s not really that bad at all compared to simplex. I’ve got a Sinclair q3220e and another can in the RX I can’t remember. But it’s not really about extending range just solidifying the coverage I have.

 

Any desense is too much. I've run plenty of 4 cavity duplexers in the scenario you describe (adding a bandpass cavity to the receive side) with absolutely no measured desense at 50 watts.

 

If you can hear desense, you're probably seeing at least 2dB of loss in the receive path. 2 dB doesn't sound like much, until you realize that 3dB better of receive sensitivity would double the coverage area of your system's portable talk in.

 

I guess it's human nature, but people will always pick the 4 watt portable over the 2 watt, yet how many of them will spend the time & money to improve the receive side of their repeater to gain 3dB? The net effect is the same. Getting 3dB of receive improvement will make your 4 watt portable seem like it's suddenly putting out 8 watts.

[WRAF213]

You can't use analog RF linking on GMRS. There's nowhere to put the links anyways. Use point-to-point Wi-Fi for building networks. If the repeater's receive side is solid in all desired locations, try improving the repeater's sensitivity with more robust filtering and a LNA before trying to figure out where you're going to put a bunch of voting receivers. Simulcasting would be overkill.

 

RTCMs don't take a 10 MHz clock directly, they require some PLL device to shift the frequency down to 9.6 MHz. There's plans to build such a device that are readily available, but there isn't an off-the-shelf solution. A 9.6 MHz OCXO would work for voting purposes as well. All of this is far more complicated than improving the repeater's receiver, since it turns a standard duplex repeater into a computer-controlled radio network.

[gortex2]

AS a few have said I'd look to increasing the performance of the current repeater. A good pre-amp and filters will go a long way. I am fortunate that I run a split antenna on my repeaters thru a combiner and multi-coupler. That allowed me a DB408 on RX and a DB404 on TX. The 408 gives me a bit better RX then adding in the pre-amp and filtering I have portables that can get in but can't hear the system. Its all about balance. I'm glad to see you have your power at a low level. Many think more power the better but thats not always the case. 

[WRFC951]

On 10/22/2019 at 8:42 AM, quarterwave said:

How about another repeater part way into the coverage area you want to expand to, and part way in the existing coverage area. Same Freqs, just use a different PL to get into the second repeater, but same output PL. 

 

Think of it as overlapping circles. 

 

I know of an entire county's fire system that was setup that way years ago, we called it poor mans trunking. 

This is what I am pondering too.  I live between two repeaters and if a 3rd could be installed that overlapped the first two our coverage area would be expanded.  I just don't know how the configuration would happen, especially if the two existing repeaters are using different frequencies.  I'm not sure if this is possible.

[WRXB215]

That is already being done. Different frequencies, different tones, linked. I talk on two of the repeaters almost every day. I've gotten to where I know right where I need to switch from one to the other.