GMRS with vehicle repeaters/relays

[n1das]

Dude, that's awesome. That's exactly what I've been wanting to build, ad been told I was nuts for trying on occasion.

Can you tell me what kind of Icom mobiles you were using? Any other secrets to building such a gadget? What questions would I ask if I knew, but don't even know to ask?

I used a pair of Icom IC-F420S UHF Part 90 mobiles. A pair of UHF GM300 mobiles would work too. There are a lot of possibilities for UHF mobiles that would work, provided they are not ham equipment. Stick to using only Part 90/95 commercial UHF mobiles.

The Icom mobiles have basic repeater control functionality built into them for building simple bare bones repeaters. I recall Icom sold a desktop repeater package based on the F320S (VHF) and F420S (UHF) mobiles. I recall it is similar to a Motorola GR300 (?) repeater based on GM300 mobiles. Audio, COR, and PTT were routed through the accessory cable on each mobile. I wired up a simple connector board for the two accessory cables to plug into. Speaker audio out of the receive mobile went through a simple high pass filter before going to the transmit mobile's audio input to make the de-emphasized audio sound a little less muddy on the air and attenuate the level. It ended up sounded as good as commercial repeater on the air. Audio volume from the receive mobile was set around 2/3 and programmed using the Minimum Volume function. The COR output (RX EXO function = ON) from the receive mobile was routed directly to the PTT input on the transmit mobile. The transmit mobile automatically generated the repeater's hang time upon releasing PTT by the receive mobile. I forget the setting in the programming that had to be enabled in the CPS to generate the hang time but it is there. I programmed a 2 second hang time. The transmit time-out timer (TOT) was set at 1 minute (default).

The receive mobile used DCS/DPL and the CSQ was set to a reasonable level. The COR output (RX EXO function = ON) is labeled as Horn Output on the accessory connector and opening CSQ AND decoding DCS/DPL pulls this output low. That's exactly what's needed to go to the PTT input on the transmit mobile. I also used the repeater with CTCSS/PL for a while. I found the DCS/DPL decode function to false decode regularly which required setting the CSQ level. The mobiles OTOH have a very stable CTCSS/PL decoder and I found I could program the CSQ level to 0 (wide open) and rely on the CTCSS/PL decode function to squelch the receiver and control the COR output. The CTCSS/PL decoder was fast enough to not leave an obnoxiously long squelch tail if the radio talking to the repeater didn't generate a reverse burst when un-keyed. All of my Part 90/95 commercial handhelds generated a reverse burst so you would never hear an annoying squelch tail when a radio un-keys.

Both mobiles were housed in an RF-tight metal NEMA/UL enclosure. Both mobiles were mounted to the inside of the enclosure for good RF grounding of the radio's casting to the enclosure. I did not use the mobile's supplied mounting bracket. One side of each mobile was bolted directly to the wall of the enclosure and I fabricated a flat metal bracket to mount the other side of both mobiles. A pattern of vent holes were drilled for airflow and an 80mm 12V DC fan was used to move air through the box and across the transmit mobile. Bulkhead mount N connectors brought RF in and out of the box. RG-142U coax was used for the internal connections to the mobiles from the bulkhead N connectors. 12V DC power input was filtered through a pair of feedthrough capacitor filters. Both mobiles were also filtered through a 12V ignition noise filter from RadioShack to filter out ignition noise and alternator whine. My car is diesel powered so there was absolutely zero ignition noise to begin with due to no spark ignition system in a diesel engine. The end result was the only RF paths in and out of the box were through the bulkhead N connectors for each mobile. The mobile duplexer I used was mounted on the outside of the box and with short RG-142U jumpers to make the connections from the mobiles (N connectors) to the duplexer.

The Icom mobiles have a high pass filter option in the programming for the receive audio to filter out any received PL tone in the receive mobile to prevent messing up PL encoding in the transmit mobile. I found it gave the audio a very distinctive band-limited "radio" quality to it. I found I got better repeat audio with this function OFF and didn't have any problem with encoding PL in the transmit mobile.

The repeater worked well overall and I used it for several years as a mobile GMRS repeater before repurposing it as a 440 ham repeater in 2011. For the 440 ham repeater project, I used an NHRC-micro controller to provide the CW ID, courtesy beep and DTMF control for the necessary ham repeater functions. The PA in the transmit mobile died while it was a ham repeater at a friend's tower site. I replaced the mobile with an Icom IC-F2020 mobile and never had a problem with it after that. The repeater no longer exists today because it was recently dismantled and replaced with a DMR repeater on 440.

 

[AronDouglas]

Most mobiles have some sort of repeater capable function built in, its just a mater of reading manuals TBA

From the looks of it, a vehicle relay is about as hard as a real GMRS repeater, requiring the same level of filtering/duplexers. So not a real challenge after all. And thanks to ICS and Open Repeater, controllers are REALLY small these days!

 

[n1das]

Most mobiles have some sort of repeater capable function built in, its just a mater of reading manuals TBA

From the looks of it, a vehicle relay is about as hard as a real GMRS repeater, requiring the same level of filtering/duplexers. So not a real challenge after all. And thanks to ICS and Open Repeater, controllers are REALLY small these days!

Yes, RTFM, LOL. I didn't have any manuals to read and learned about the features through exploring the radio's features in the CPS. I was using the old DOS-based CSF-300S CPS back then.

No controller was used with the mobile GMRS repeater because of the basic repeater control functions built into the mobiles and no CW ID required for a GMRS repeater. The 440 ham repeater project used an NHRC-micro controller for the CW ID, courtesy beep, DTMF control and the necessary ham repeater control functions. It was real easy to add the NHRC-micro controller to what I had already built. The NHRC-micro is the size of a Comm Spec PL board and can be mounted inside a mobile.

I agree with you, a mobile GMRS repeater is a real GMRS repeater and has all of the same challenges to deal with when it comes to antennas and filtering/duplexers. The difference is the repeater setup is installed in a vehicle instead of at home or at a tower site. I found it real handy to have a local on-site GMRS repeater to use wherever I went.

I never went out of range of the repeater while driving because it was in the car with me at all times.

 

[quarterwave]

To the OP...

If you all, or maybe just those who venture out, have phones and data service on the property, how about setting up a private Zello channel and link a PC with a control station.

Honestly 600 acres should be easy to cover (handhelds) with a modest repeater, though. Don't over think this.

 

[wowologist]

part 1 - IMHO ~ You may be "overthinking" this basically because you may have not used a system yet... I might suggest ordering the common (here come the trolls, I know their not type certified ...but seriously?) baofeng hand helds off of your china mart of choice and do a little research on GMRS repeaters in your area already (if none, GREAT be a do-er not a follower! see part 2) Here in the SF bay area we have a plethora of some very strong systems that reach well over ~75 miles and are accessible with 4w HT (~8-12miles IN TO the repeater, 35-45miles with a mobile) because their owners are really into that part of doing it right and utilize well thought out antenna placement and equipment etc. Always check in with the repeater OP and ask for permission to use it and start yapping! - just because the repeater is accessible publicly and you are licensed does not mean you have automatic privileges to utilize it, as it is someone else's' property. The VRS "system" that your ?wanting? to utilize would really be a waste and unless you're in really, really, really mountainous terrain wouldn't really serve a purpose greater than having a fixed site with good eyes(reception area, and if that is the area you're intending to do this in...you would want to stick to a VHF-Lo system)

part 2 - if there really are NO GMRS repeaters operating in your neck of the woods GREAT you won't need to coordinate frequencies with others and can pick a set at random and set up shop. If you have a barn (you said you had acreage so growing up in really north California on 2000 acres I couldn't imagine the word acres being used without having a barn!!) your antenna is limited to 20' above the HIGHEST point the antenna is mounted UPON. I myself use TYT mobiles (40w) and TYT/Wouxon HT's and a 60$ china mart UHF duplexer, arrow antenna and they work like a charm.

...and now its dinner time so I will have to finish this up later.

 

[a417]

Most mobiles have some sort of repeater capable function built in, its just a mater of reading manuals TBA

I'd go with some, not most. Part 90 not so much, part 95 well....anything goes.

 

[n1das]

I'd go with some, not most. Part 90 not so much, part 95 well....anything goes.

I used Icom IC-F420S mobiles which are Part 90 mobiles. I know some but not all Part 90 mobiles have basic repeater control capabilities built into them. I recall Icom also sold a desktop repeater chassis based on a pair of these mobiles. It reminds me of a Motorola GR300 (?) desktop repeater package that was based on a pair of GM300 mobiles. One of these repeater packages might work for the OP for building a mobile GMRS repeater setup like what I had.

I later repurposed the repeater setup as a 440 ham repeater. It has since been replaced with DMR repeater on 440.

I thought about putting a GMRS repeater up again but decided it's not worth it. The vast majority of my use of GMRS/FRS over the years has been for local simplex type ops. I don't use GMRS/FRS at all anymore since moving my local on-site simplex operation with family and friends to 900MHz using Motorola DTR and DLR series FHSS digital radios. A coworker once asked me why not just use FRS? My answer was that I've already been doing that since FRS was first created in 1996 and longer than that as a GMRS licensee since 1992 and using good quality equipment. I want a secure, all-digital solution that's higher quality and more professional than FRS. I don't bother with GMRS/FRS at all anymore because the DTRs and DLRs work so well for my use. I've been bit by the digital radio bug.


Sent from my XP8800 using Tapatalk

 

[a417]

I used Icom IC-F420S mobiles which are Part 90 mobiles. I know some but not all Part 90 mobiles have basic repeater control capabilities built into them. I recall Icom also sold a desktop repeater chassis based on a pair of these mobiles.

I will disagree with you on this, having the requisite functions of the building blocks of a repeater does not make them having "basic repeater control capabilities". Taking two GM300s and building it into the GR300 is not the same beast. They are each building blocks of a larger system. I would agree with you if you said that the radios had the functionality necessary to be built into a repeater system, but not that they have basic repeater control capabilities.

An example of a built in repeater functionality would be Kenwood and the x90 dual deck system. If you take a (for instance) a TK690 & a TK790 and install them together, they function as 1 radio. The software allows for an actual repeater function to cross-band the VHF & UHF deck and give you a barebones cross band repeater (albeit no controller, IDer, but it does have a TOT). They fully function as a radio until the button is pushed to become a repeater, then they're a repeater. It was actually a very durable and flexible dual band, high power unit all things considered...dumb, but durable.

As for running a mobile repeater...
You would need to contain all this within the limits of your FCC license, which means the existing 462/467MHz frequencies. For a mobile repeater to work well you'll need lots of frequency separation, and you're going to have an extremely hard time getting that with the limitations. The filtering required gets expensive and complex.

I understand what you are looking for, but using GMRS and an SVR and connecting back into your own repeater is going to be a challenge.

I can't emphasis how accurate this above quote is.

So less than 2 square miles. Easily doable using a repeater and portables, 15miles using mobiles is also doable.

[snip]

A mobile repeater should be just taken completely off the table for this application.

This. this this this.

A well placed antenna, a solid setup, and run portables. Mobile repeaters and SVRs with lots of moving pieces are just moving headaches. The OP may have overestimated his original need for a unique solution, and underestimated a well thought, simplest/fewest moving pieces installation.

 

[K4KDE]

I am curious, wouldn't a smart phone be a better choice since everyone already has the phone ?
I dont know the first thing about GMRS and it's advantages.
thank you for letting me interrup

Just going to leave these here for everyone;

Wireless Carriers Report Service Down in Some Irma-Hit Areas

Cable and wireless service providers are still grappling with the fallout after Hurricane Irma struck Florida over the weekend. Carriers are getting a better idea of the damage the storm caused and the work ahead that will be needed to restore service.

www.bloomberg.com

Hurricane Harvey Knocked Out Cell Service. Now Calls for Backup Wireless Power Are Rising

"It’s a huge public safety issue"

fortune.com

Don't Count On Your Cell Phone For Help After The Next Huge Hurricane

Don't Count On Your Cell Phone For Help After The Next Huge Hurricane

www.huffpost.com

 

[Justintime1989]

To get frequency separation you could use an itinerant business channel like 154.600 to link to a GMRS radio. Not exactly legal but the FCC doesn't do much enforcement these days.