Channel Guide

Stuff On This Page:

1. CAVERN Channels & Radios Explained
• Retevis RT22 FRS Channels
• BTech GMRS v1 Channels

2. CAVERN Just Had to Be Special
• Group Channels Map

3. CAVERN Repeater Channels
• Main Channel @ Repeater 1
• CAVERN Emergency Alert Channel

4. CAVERN Channel Reference
• Channel Grid

CAVERN Channel Guide (PDF download)
• Playing Nice (Interoperability Notes)
• An Emergency Situation Example
— Why Make a Big Mesh? (The Future VERN)


1. CAVERN Channels & Radios Explained

About our Recommended Radios:
• FRS: Retevis RT22
• GMRS: BTech GRMS V1
We chose these radios because they are low-cost and have good power specs and programmable channels. This is not an endorsement: many other radios can be made to work quite well, and CAVERN volunteers can probably help you program your radio for easy operation. Send email to NetCon for assistance with these or other radios you may already own.

• Retevis RT22 FRS Channels:

The standard radio channels in CAVERN’s pre-programmed Retevis RT22 and BTech V1 radios are identical to most factory programmed FRS/GMRS radios, but only for the first seven (7) channels. This was because the best choice for a low-cost, higher-power (2-Watt!) was the RT22 radio, but it only offers a memory locations for 16 FRS channels (not the full 22, which is normal). Also, for FRS channels from 8 to 14, we cannot reduce the radio’s power to transmit at the legally required 0.5 Watts (so we left those out… for now). That left us locations 8-16 for the remaining 8 FRS/GRMS channels, including one extra location for a special alert-only channel (see below).

Fortunately, we only needed a few channels to get our six (6) Groups started on the radio (their origin was our local FireWise program). The RT22, at 2.0 Watts, is also quite a powerful little FRS radio and we can program it to work with our Repeater. Pretty much a win-win-win because we don’t really need those extra channels for the Cobb Area VERN*.

• BTech GMRS v1 Channels

CAVERN programmed BTECH GMRS V1 radios are arranged like most GMRS repeater capable radios with channel locations 1-22 corresponding to the standard GMRS channels. Channel locations 23-30 are the 8 repeater-capable channels (which output on FRS/GMRS channels 15-22).


In practical terms, Channels 1-7 on the CAVERN pre–programmed FRS and GMRS radios play nicely with other standard radios. CAVERN’s Retevis RT22 FRS and BTech GMRS V1 radios will interoperate (transmit/receive) with many off-the-shelf FRS & GMRS radios, such as you might overhear other families using at supermarkets, beaches, water parks, shopping malls, wilderness areas, etc. When we use those channels (not often), it’s for direct communications between two radios (aka “simplex”, which does not use the Repeater) within one of our six groups. For the lower-power FRS radios, this normally requires “line-of-sight” between the radios.

Example: someone in Group 3, our BottleRock group, might talk on Channel Location 3 with someone else in the BottleRock group who is using a standard, off-the-shelf FRS radio. Thus, if there’s an emergency, even non-CAVERN operators can receive relayed information through others nearby in their Group’s area. And they can use a radio they already have — even without the CAVERN programming.

* Networks elsewhere might well need more channels, so eventually we’ll address those needs on the VERN project website.


2. CAVERN Just Had to Be Special

CAVERN radio programming DOES NOT conform to FRS and GMRS standards on FRS Channels 8-16 and GMRS Channels 15-22. Here’s why:

The vast majority of CAVERN network communications go through our Main Repeater. Our Repeater 1 is located in Group 4 on Hobergs Hill (overlooking the resort destroyed in the 2015 Valley fire). That’s a centrally-located high vantage point that can ‘see’ a significant amount of the terrain within the other five CAVERN Group areas (see the Group Channels Map below). We are working on a plan to elevate Repeater 1 so it’s even higher up and can reach more of the people in all six groups. This is helpful for connecting GMRS radio operators with higher-powered radios (typically 5 Watts) who can relay information between entire neighborhoods/groups over longer distances. On radios we pre-program for CAVERN operators, that corresponds to:
FRS Channel Location 8 and
GMRS Channel Location 23

BUT !!!** We also add special security tones to ensure that our local volunteers have the primary access to the Repeater, which also broadcasts on one frequency (output) and receives signals on another (input). These tones and different input/output frequencies do not provide much security or privacy, but they can limit most Repeater traffic to our public safety uses. More on that below…

• Group Channels Map

CAVERN’s six Groups (the Repeater is in the center of Group 4)

** I do like an emboldened but, I cannot lie.


3. CAVERN Repeater Channels

CAVERN Repeater 1 (Frequencies in MHz):
462.550 | Output
467.550 | Input

• Main Channel @ Repeater 1

The Main Channel uses a “DCS” tone of D071N (or 071N). The Main Channel is for daily updates & messages, weekly check-ins and other general community radio communications.

The DCS tone for the Main Channel is pre-programmed into any GMRS radio you acquire through CAVERN on Channel Location 23 (GMRS). CAVERN programmed FRS radios can only monitor the Main Repeater (including the Emergency Alerts) at Channel Location 8 until updated.

• CAVERN Emergency Alert Channel

The Emergency Alert Channel uses a CTCSS tone of 103.5 hertz, and is ONLY for the purpose of alerting everyone in the Cobb Area to a serious emergency situation. Folks can monitor this channel 24/7/365 and only hear alerts (and occasional tests).

The CTCSS tone for the Emergency Alert Channel is pre-programmed into any FRS/GMRS radio you acquire through CAVERN, and configured as Channel Location 9 (FRS) and Channel Location 33 (GMRS).

Note: you can learn to program radios yourself, but you’ll need special cables, frequency/tone data and, well, unless you’re a radio nerd, it’s a lot easier to get them through us. As a bonus, our friendly neighborhood radio nerd (Mel), also adds a lot of local emergency responder channels into CAVERN’s programs. That includes Police, Sheriff, CalFire Tactical, AirTankers, etc, for those fine upstanding citizens who scan the airwaves and listen to what the local agencies are up to. Indeed, some CAVERN operators, because of their location, equipment and expertise, can hear certain information being broadcast better than most and relay it to the entire network.


4. CAVERN Channel Reference

To help new CAVERN operators understand how our BTech GMRS v1, and Retevis RT22 FRS channel locations correspond to standard FRS & GMRS channel locations, we prepared a downloadable data sheet.

The Guide shows: “Standard” FRS & GMRS channel locations for most non-CAVERN radios (i.e. the “factory settings”), and; the corresponding pre-programmed CAVERN channel locations for both of our recommended FRS and GMRS, plus; additional CAVERN Repeater Frequency & Tone settings for radios (i.e. to help limit Main Repeater access to Cobb Area volunteers) and some additional notes.

NOTE: If you need help after you review the Channel Guide, please email NetCon.

Playing Nice (Interoperability Notes)

In 2017, the FCC changed its rules to allow FRS use on channels 15-22 and made our network possible. The new channel rules mean that cheap low-powered FRS radios (which require no license) can now share repeater output channels that were previously reserved for high-powered GMRS radios (which require an FCC license).

This is both an opportunity and a challenge. FRS radios (0.5—2.0 watts) are short range devices that can realistically only reach other radios in a neighborhood where you have  “line-of-sight” between radios (usually up to a mile or so). GMRS radios (5-50 watts) can often reach radios several miles away, sometimes, depending on various conditions, they can even transmit and receive signals from over 100 miles away! GMRS radios can access the 50-Watt CAVERN Repeater 1, which electronically relays the transmission throughout the Cobb area and to points beyond. FRS radios can hear these transmissions (very important for alerts) but often cannot reply back to the GMRS operator talking because they are too far away or lack the power.

This is where our human network can shine! By positioning more and more CAVERN-trained GMRS operators around the Cobb area, our goal is to make it possible for FRS radios (even the toy FRS radios families use at amusement parks, etc.) to get their messages relayed around the mountain and even to the surrounding communities. We need more GMRS licensed radio operators in all six of our CAVERN Groups! Send an email to NetCon and we can help you upgrade to a GMRS radio!

• An Emergency Situation Example:

Seigler 031 sees a fire, but does not have a cellphone signal, so she sends out an immediate alert on Ch 9 (the Emergency Alert Channel, see above) using the handy little Retevis RT22 FRS radio she carries around with her.

Seigler 006 is monitoring Emergency Alerts on a BTech GMRS radio set to Ch 33 (alerts only) and hears the Alert. Siegler 006 immediately calls 911 and then uses his 5-Watt BTech GMRS radio, set to Ch 23 with the Emergency Alert tone (see Channel Guide) to alert everyone throughout the Cobb area who may be listening for Emergency Alerts on the CAVERN network.

Boggs 143 asks for clarification using an RT22 FRS set to Ch 8 (‘simplex’ only), but is too far away to be heard by the Seigler operators.

Bottlerock 001, a GMRS operator monitoring the repeater with a much more powerful GMRS radio set to Ch 23 using the normal repeater tone, notices that Boggs 143 has not received a clarification. So, BottleRock 001 relays Bogg 143’s question through the repeater to Siegler 031, who answers the question. BottleRock 001 then relays that clarification back to Boggs 143.

As CAVERN grows (and the local population increases over time), Group Channels 1-6 may become increasingly useful for daily neighborhood communications (and we may more channels!). Group Channels were intended for use withing specific neighborhoods (see map), where these simplex-only (radio-to-radio) non-repeater channels put FRS and GMRS radios on a slightly more equal footing (range-wise) despite the difference in power (2W vs 5W). As these channels start to be used more and more, GMRS operators will want to monitor their local neighborhood’s Group Channel from time to time and relay that local traffic, if appropriate, using the Repeater to the entire CAVERN network.

Why Make a Big Mesh? (The VERN Future)

Someday, once we get support for the VERN project from a variety of sources (crowdfunding, grants, donations, etc.), we plan to make a radio mesh network available to Everyone Everywhere. People will be able to use a smartphone app to do many more things to protect themselves and their community, and much more efficiently, regardless of the topography where they live. And we’ll only need radio repeater(s) as backup.

A mesh network is not affected by difficult, mountainous terrain: it can reach every household in an area where people have nodes on their roofs (powered by the Sun!). When people register their account (or their rooftop node) they are pre-assigned to a group based on their home location. The mesh’s database uses cryptographic authentication to automagically recognize each registered CAVERN operator who logs in. And there privacy-enhancing features are possible: the mesh can protect your physical location from discovery by unauthorized persons, and in an emergency —even if there’s no GPS available!— the Mesh can triangulate your location and send that to Emergency Responders so they can find you quickly. There are many more things possible with the Mesh of the future, including delivering high-speed connectivity to remote areas without needing to microwave peoples’ brains with 5G just because some big corporation$ think that’s cool.

Our proposed Mesh is also a supernet. That means it keeps running even when the rest of the telecommunications infrastructure goes down. And it will go down hard at some point, Ozymandias! Meanwhile, imagine a scenario where the Internet’s backbone goes down for a while. Maybe a fishing boat somewhere off a coast dragged its little anchor over the wrong transoceanic fiber bundle (again). Maybe a meteor shower (or something resembling one) took out a few choice satellites and plinked a few groundstations. Maybe some people did something: you know how people can be, right? Too much hair dye or tanning bed time and someone, somewhere loses and eye. So, the Internet we take for granted today looks like it needs a Plan B, and a mesh that connects everyone to everyone else without corporate middlemen seems like a reasonable one.

Soon, you’ll be able to learn more about this R&D work at our VERN website (currently under construction). Please be patient and send lots of R&D donation support! 🙂