Mon 30 Sept 2019
  KPFZ 88.1 FM
   (Lake County public radio)

Episode 186 from Thank you Ben!

CAVERN’s organizers were live on the air with radio host Ben Weiss on public radio station KPFZ, chatting about the CAVERN project and its roots, RF radio topics, organizing your community to be prepared for emergencies and the future convergence of software-defined radio (SDR) and terrestrial radio mesh networks, including the mothership VERN project’s development happening at a small nonprofit tech thinktank right here in Lake County.

Useful Links (WIP)


CalFire Incidents:

GMRS /FRS / Radio


Cobb (under construction, needs volunteers!)


Sonoma County Emergency:

CAVERN project (Firewise) Groups

RT22 Channels Explained

CAVERN’s preprogrammed Retevis RT 22 radios channels match the way most FRS/GMRS radios are programmed, but only for the first few channels. This is because the RT22 only has 16 channels and cannot transmit at the legally required 0.5 Watts for FRS channels 8-14 (so we left those out for now). What this means in practical terms is that on the CAVERN-programmed “Retevis RT22” (FRS) radios, channels 1-7 correspond to most other off-the-shelf FRS radios, BUT channels 8-16 do not. Refer to this table:

1 (Group 1 – Boggs)1
2 (Group 2 – Cobb)2
3 (Group 3 – Bottlerock)3
4 (Group 4 – Hobergs)4
5 (Group 5 – Seigler)5
6 (Group 6 – Hannah)6
7 (Group 7 – TBD)7
8 (CAVERN Main/Talk)15
9 (CAVERN Emergency Alerts)15 (+ 103.5 hz tone AKA tone #13 )

CAVERN Emergency Channel

Not everyone wants to listen to a scanner or CAVERN throughout the day…and especially at night. Luckily CAVERN programmed radios can screen out the day–to-day chitchat on the frequency, so that you only hear alerts of local emergencies put out by fellow CAVERN volunteers.


To screen out chitchat set your CAVERN-programmed RETEVIS RT22 to channel 9, or (newer)BTECH GMRS V1 to channel 33. Additionally any FRS/GMRS radio that supports privacy tones can be set to channel 15 with a “privacy” or CTCSS receive tone of 103.5 Hz. Consult your manual or (Often tone #13 corresponds to 103.5 Hz.)

NOTE: We test the tone at the beginning of Net check-ins or when a Fire siren is tested BUT we conduct actual check-ins on non-emergency channels! (RT22 ch8, V1 ch 15 or 23, most FRS/GMRS radio ch.15 with NO privacy tone.) So reset your radio after test or you may not hear anything!


Should you need to announce an emergency, first listen and ask on the non-emergency channel if the network is already aware of the emergency.

If there is imminent danger to the some part of the Cobb area (as in a moving fire within 1-3 miles likely to require evacuation) put out an emergency alert with as much detail RETEVIS RT22 to Ch .9, or BTECH GMRS V1 to channel 15 or 23 with CTCSS 103.5 set on transmit. Additionally any FRS/GMRS radio that supports privacy tones can be set to channel 15 with a “privacy” or CTCSS tone corresponding to 103.5 Hz (often named tone #13).

CAVERN Check-Ins: a “How To” Guide

About CAVERN Check-Ins

Anyone who can hear the CAVERN radio network is welcome to check in: you don’t necessarily need a ‘Callsign’ or a CAVERN ID (at least not the first couple of times). You can start out by checking in with just your first name or even a “handle” (i.e. a nickname).

We begin each weekly Check-In by testing our Emergency Alert channel. We do this, a few minutes before the main check-in starts, to make sure everyone is able to tune their radios to hear emergency alerts ONLY (if people want to, they can ignore the normal daily patter on our main repeater channel). Once we’ve given everyone about five minutes to confirm their ability to hear the Emergency Alert Channel (see the right-hand sidebar: we generally program these channels into peoples’ radios for them), then we proceed with the main Check-in, which is a roll call led by a Network Control person and organized by CAVERN groups in order*.

* We check in our Cobb Area Volunteer Emergency Radio Network operators starting from Group 1 through Group 6 and even to ‘Beyond’ the local area. Radio waves can propagate over very long distances. We have spoken to radio operators as far away as Signal Peak in the Sierra Nevada mountains. That’s 120+ miles east, using just a 5-Watt GMRS radio (and direct line-of-sight)!

CAVERN Groups 1—6
CAVERN Groups 1 through 6.

The CAVERN Directed Net

CAVERN is a Directed Net, meaning that, while any network session is in operation (usually for less than an hour), all communications go through a person who serves as “Network Control” (aka “NetCon”). Whoever is NetCon during the network session, that’s the person running the network, queueing people up in an orderly way so they don’t ‘step on’ each others’ transmissions (see Note #1). Basically, you don’t transmit until given the go-ahead, and if you need to interject anything, you first ask for permission as briefly as possible. To ask NetCon for permission to speak next, you use short phrases such as: “net control <your first name>” or “net control, comment…”. When NetCon says to go ahead, then you proceed with your “traffic” (i.e. your transmission or communication).

1. For more info on our implementation of the Directed Network protocol, which is very practical for effective emergency communications, see: “Intro to Network Control“.
2. Leave breathing room on the Airwaves: after anyone speaks, everyone should allow a few beats so NetCon can queue the next speaker. Sometimes, it’s so someone can answer your question (other than NetCon).
3. In the world of FCC-licensed GMRS radio operators (which is a different world from the unlicensed Citizen’s Band radio, or “CB”, familiar to fans of the Smokey & The Bandit movies), we reserve the word “break” ONLY for extreme emergencies. You will probably never say “break” on the CAVERN network: if anyone does, it’s probably bad news for everyone (e.g. a wildfire or storm damage).
4. Comments (i.e. non-roll-call messages) should benefit all listeners on the network.
5. We make time for casual chats among members after we close the net and release the frequency for general traffic.

CAVERN Check-In Protocol

Check-Ins start with Group 1 (download the sample check-in script at the ‘Intro to Net Control‘ link in Note #1 above). When you hear NetCon call for your Group by its number: first listen for the Licensed GMRS radio operators in your group to check in (they often have a lower number and can hear more people with their higher-powered radios); then check in by the order of your CAVERN ID. If you’re #5 in your group, you’ll go, and #6 checks in after you, etc.

Say your first name plus your CAVERN ID (or GMRS callsign, if you have one) to check in. That’s really all there is to it! For example: “Betty at Seigler 87, checking in” or “Angelo, WRCE720, checking in”. If you don’t know your CAVERN ID or don’t have one yet, no problem: just use your first name or a “handle” (a nickname, like “Pink Panther”). We understand that some shy woodland creatures may want to remain pseudonymous or that some parents prefer their kids not to use real names: that’s perfectly OK. The important thing is to use a persistent pseudonym to identify yourself so others can reach out to you reliably in an emergency.

If at first you do not succeed by immediately hearing acknowledgement from NetCon, just try checking in again. You can even check in later during another group’s time (anyone from the first few groups can check in late during any group’s slot or at the end).

You can also ask someone who you can hear and you can probably heat NetCon to “relay” your check-in for you. If you can hear a weak signal/distant station that NetCon does not seem to hear, during a gap you can say “net control, relay…” and, as soon as NetCon gives you the go-ahead, pass on the info you heard. (Expert Tip: listen with your radio’s “squelchoff, or very low, to hear weak stations.)

If you have a question for NetCon, during a check-in, just say “net control, question” and ask it when your turn comes (e.g. “how do I turn my squelch down?”). For more detailed questions, please send Network Control an email.

How To Relay Check Ins

Sometimes, people who are clearly audible to you cannot be heard by Network Control. In those cases, you can be the “relay” between them and the other people on CAVERN’s network. In fact, in a serious emergency, the ability to relay for neighbors can be a potential lifesaver for you or those near you. Happily, there’s an easy protocol for relaying signals this way. Here’s what it might sound like:

Hannah 1: “NetCon, Relay…”
Net Control: “Hannah 1, go with your relay…”
Hannah 1: “Relay for Hannah 22.”
Net Control: “Copy, Brett: 22 is checked in…”

How NOT to Check In

Hannah 13: “Achey-breaker-break. This is Hannah 13 aka Josh the Radio Dude, aka Whiskey Tangle Foxtail Doohickey 7-4 Niner. I’m hearing someone pretty weak out there… might be Brenda? I dunno… hey, I really like the new website, you guys! Anyway, go ahead and check in my dog Jasper, my pet iguana Tickles, my cockateel Snorton Buffalo Wings III… oh, and me, Josh the Radio Dude… (Awe-sooome!) Kay… I’m gonna go have some lunch now. This has been amazing as usual. Back to you, Mr Networky Dude.”
Net Control: “Uh… Josh, your super-long transmission stepped on Brett’s urgent relay. Brett, please repeat your relay… go ahead…”

In the “not” example above, try replacing the word “relay” with the phrase “urgent wildfire alert!”. Can you understand why worried people under the imminent threat of a wildfire would not be that interested in your pets’ names or your lunch plans? Would your otherwise “awesome” sense of humor be appropriate in such a situation? Maybe you see why rehearsing network protocol is important…? Remember: we’re practicing for life-and-death situations that are guaranteed to happen someday. We all need to be ready to communicate what we know (or need to know) in the most professional way possible, especially when talking to emergency responders. Be like “Brett/Hannah 1” below. Short & Sweet!

2019 Kincade Fire glow
2019 Kincade Fire glow, just west of Cobb Mtn.

July 2019 original: Mel
Feb 2020 upgrade: Dav

Operating Your CAVERN Radios

CAVERN Network Control distributes these two inexpensive radios to our member operators with pre-programmed channels to make it easy for you to listen and join in.

1. CAVERN-Programmed RETEVIS RT22 Radio

Operating the CAVERN-programmed RETEVIS RT22 (starts at 3:30) This old video with bad audio will be replaced soon!
  • Tap “+/-” button to change the channel.
  • Ch.8 is the day-to-day chat and check-in channel for CAVERN.
  • Ch.9 is for emergency announcements and (siren) tests.
  • Hold down the “—” (minus sign) key until you hear an “on” prompt to scan all 16 channels. Hold again to turn “off.”
  • Press and hold down the “+” (plus sign) key until you hear static to “turn off squelch” and hear weak stations.
  • Keep your radio on 24/7 so you don’t miss emergencies and other alerts.
  • To maintain good battery life, periodically take your RT22 radio out of its charger for a few hours (keep it on!) instead of always leaving it plugged in (e.g. rotate 2+ radios on/off the charger).

2. CAVERN-Programmed BTech GMRS-V1 Radio

Until there is a full write-up here, please read’s easy-to-read guide. Note: guide says “All programming must be done in the Frequency Mode.” Not true: we list some exceptions, and a few helpful notes, below:

  • If you hold the “F” button down too long you will get a big surprise (and so will anyone listening!) Try to avoid doing that accidentally. (Read Miklor to find out!)
  • “M” button takes the squelch off (squelch suppresses noise but may also suppress weak signals)
  • Ch 15 “GMRS 15” bypasses the repeater. Good for talking to your local group.
  • Ch 000 is (or should be) “CF LNUE” which stands for CalFire Lake-Napa-Unit-East. That is the Cobb area’s CalFire dispatch center located in St. Helena. You can monitor this channel for initial Fire dispatch calls.
  • Ch 33 monitors CAVERN for Emergency-only transmissions BUT DOES NOT TRANSMIT.
  • To transmit an emergency alert: Ch 023 [MENU]1,3 [MENU] (display=”T-CTCS” prompt says “CTCSS”)1,0,3,5[MENU]=”confirm(ed)” (See video below)
  • [MENU] 41 SC-ADD adds or removes that channel from scan. Very handy if you have a noisy channel you’d rather skip!
  • Scan Button is the “*”. Prompt says “Scanning Begin”… (it sounds like “scanning beacon” due to the accent)
  • The “#” button locks the keys. Set the upper band to “000” and the lower band to “023” and you can safely put your radio in your pocket!).
CAVERN GMRS Operators listen up! Here’s how to program your radio for Emergency transmit.

Recommended Radios for CAVERN

Most FRS or GMRS radios will work CAVERN however we’ve made it easy with 2 pre-programmed FCC approved radios.


The RT22 is one of the first high power 2 watt FRS radios available. It is FCC type 95 approved (meaning legal to use without a license*.) We buy them in bulk so a pair can be had for a mere $25 already programmed (and that price will drop soon!) these are short range radios 1/2 mile to 2 miles is the practical range, great for connecting a neighborhood. Contact for information or to get one.


The BTECH GMRS-V1 is a 5 Watt GMRS repeater capable radio/scanner. Transmitting requires a GMRS $70 10-year family license. It can be purchased directly from Amazon but often has some pre-programmed on hand. Price varies $50-60. Practical range is 1-5 miles but with a repeater 20-100+ is normal. Also works as a scanner which can monitor Calfire, Sheriff, weather, Ham radio and more.

Other Radios
Popular FRS radios

Most FRS radios can access the CAVERN channel and GMRS radios the CAVERN repeater. In addition many 10-50 watt commercial mobile radios can be programmed for CAVERN. Contact if you already have a radio or are interested in high power GMRS.

* technically when you operate an FRS radio you are automatically “licensed by rule.”