Retevis RT3S: setup and building a codeplug from scratch

The Retevis RT3S is one of the most popular budget dual-band DMR radios out there, and it is almost always a ham's first digital handheld. The radio ships with a Chinese factory codeplug stuffed with utility frequencies, and in that state it receives nothing useful. To bring the radio to life on the amateur bands and on your DMR network, it needs to be fully reprogrammed. Let's walk through the whole path from scratch: which cable and CPS you need, how to build a working codeplug by hand, how to write it to the radio, and the pitfalls waiting at every step.

First things first: the RT3S is almost a complete hardware twin of the TYT MD-UV390 — it is the same platform under different brand names. So everything written here about setting up the RT3S applies, with minor caveats, to the MD-UV390/UV380 as well. If the general codeplug theory hasn't clicked yet, keep our breakdown of what a codeplug is and what it consists of handy.

What this radio is and who it suits

The RT3S is a handheld built on the AT1846S chip with two bands: VHF (136–174 MHz) and UHF (400–480 MHz, up to 470 on some revisions). It works in two modes: digital DMR (Tier I/II) and plain analog FM. Power is stepped, up to roughly 5 W at maximum, and the case offers moderate IP protection — this is a consumer-grade amateur class, not professional "armor."

• Who it suits. A beginner who wants to get into DMR cheaply and not be tied to a single band. A dual-bander is handy: on 70 cm you work through DMR repeaters and a hotspot, while on 2 m you keep local analog channels.
• Strong points. Price, two bands, support for a digital contact list with tens of thousands of entries, and compatibility with open tools and firmware for the MD-UV3xx platform.
• Weak spots. The factory CPS is unintuitive, documentation is sparse, and different batches have minor firmware differences. So we work strictly step by step and don't blindly trust "someone else's" ready-made codeplugs.

Cable and CPS: where setup begins

The RT3S is programmed only from a computer using the manufacturer's software. You need two things: the right cable and the right CPS version.

1. Cable. The Retevis/TYT cable bundled for the MD-UV3xx is a USB cable with a built-in controller (when connected, the radio shows up as a HID/COM device, not as an ordinary CH340 USB-serial). Cheap universal "Kenwood programmers" with two jacks won't work here. If the cable isn't detected, the problem is almost always the cable itself or the driver — details in our article on programming cables and drivers.
2. CPS. Download the CPS strictly for the RT3S from the Retevis site or a trusted mirror, matching your firmware version. The CPS version must match the generation of the radio's firmware, otherwise reading/writing will give you an error or garbled channels.
3. First-connection order. Install the CPS and driver, connect the radio while it's off, turn it on, let Windows detect the device, and only then start a read.

The iron rule before any experiments: first read the factory codeplug from the radio (Read) and save it to a file as a backup. If something goes wrong, you can always restore the radio to its original state.

Building the codeplug: contacts and talkgroups

The logic for assembling a codeplug in the RT3S is bottom-up: first the reference entities (contacts, receive lists), then the channels that reference them, and finally the zones that group the channels. If you try to go in the reverse order, half your fields will have nothing to fill them with.

We start with digital contacts (Digital Contacts). In DMR a "contact" is not a person but a call destination: a talkgroup (group call) or a specific DMR ID (private call). Create one entry per group you plan to listen to and transmit on.

• Name — human-readable, for example DMRhub General or TG Local.
• Call Type — Group Call for a talkgroup, Private Call for a direct call to a subscriber.
• Call ID — the talkgroup number or the subscriber's DMR ID.

In parallel, fill in your own Radio ID field (the radio's own DMR ID) in the general settings section. Without your own DMR ID you won't get on the air properly: the network simply won't accept a call from a zero or borrowed ID. The ID is issued free of charge — how to get it is described in our guide to DMR ID registration; on the DMRhub portal the number is issued straight from your dashboard.

RX Group List: what the radio will listen to

The next step is the RX Group List. This is the set of talkgroups the radio will receive on a given digital channel in addition to the group you transmit to. Without a properly built receive list you'll talk but won't hear replies from neighboring groups — the classic beginner complaint of "I transmit, they hear me, but I hear no one."

Create one or two receive lists (for example, "Network" with all the groups of your DMR network) and include the needed contact-groups in them. One list is then reused across many channels. The logic is covered in detail in a separate article on the RX Group List and receiving groups — I strongly recommend reading it, this is the spot that most often breaks the link.

Channels: frequency, Color Code, time slot TS2

Now the most important part — the channels (Channels). Each digital channel in the RT3S is a bundle of a frequency, DMR parameters, and references to the contacts and receive list you created earlier. The minimal set of fields for a digital channel:

• Channel Mode — Digital for DMR (or Analog for FM channels).
• RX/TX Frequency — the receive and transmit frequencies. For simplex (direct contact and most hotspots) RX = TX. For a repeater, TX is offset by the shift amount.
• Color Code — the color code, the digital analog of a CTCSS "password." It must exactly match what's set on the repeater or hotspot. A mismatch, and the channel is silent as a fish. What it is and why — in our breakdown of Color Code.
• Time Slot — the time slot, TS1 or TS2. For a hotspot and most simplex scenarios you almost always use TS2 — remember this as the default value.
• Contact (TX Contact) — the talkgroup your voice goes to when you key the PTT.
• RX Group List — the receive list you assembled earlier.
• Admit Criteria — the condition for going on the air; for discipline on a shared network, set Color Code free (transmit only when the slot is free).

A practical example of a channel for your DMR network's hotspot: RX = TX = the hotspot frequency (for example, in the 70 cm amateur segment), Color Code = 1, Time Slot = TS2, TX Contact = "DMRhub General", RX Group List = "Network", Admit = Color Code free. Make one such channel for each frequently used group — switching between groups is easier by selecting a channel than by manual entry.

Zones: bringing order to your channels

When you have more than a dozen channels, it's easy to drown in them. That's what zones (Zones) are for — folders that group channels by purpose: "Hotspot", "City repeaters", "Analog 2 m", "Reserve". The RT3S switches between zones from the front panel, and within a zone between channels using the knob/buttons.

A sensible zone structure saves your nerves on the air: you don't scroll through a hundred channels, you jump straight to the folder you need. How to lay out channels into zones properly and not duplicate them is covered in a separate article on zones in a codeplug.

Writing to the radio and switching to amateur mode

Once the codeplug is assembled, before you write it — double-check your Radio ID, Color Code, and time slots on the key channels again. Then:

1. Connect the radio with the cable and turn it on.
2. In the CPS run Write (writing the codeplug to the radio). Don't disconnect the cable or turn off the radio during the write.
3. After the write the radio will reboot. Check that your zones and channels have appeared.

About "amateur mode" and frequencies. The RT3S has no separate "ham mode" toggle — the range of operating frequencies is determined by the firmware and by what you entered in the channels. The factory version usually already covers the amateur segments 144–146 and 430–440 MHz; you simply set up channels on the needed frequencies. If the radio refuses to transmit on some frequency ("TX inhibit"), it means the frequency is outside the window allowed by the firmware — that's a limitation of the specific firmware, not of your setup. Don't go beyond the amateur segments and observe the terms of your license and local frequency-use rules.

Typical beginner mistakes

• Radio ID not filled in — the radio transmits "into the void," the network doesn't see it.
• Color Code or time slot doesn't match the hotspot/repeater — the channel is silent in both directions. Check this first of all.
• Empty or wrong RX Group List — you only hear the group you transmit to, neighbors' replies vanish.
• RX ≠ TX on simplex — you accidentally entered a repeater shift where it isn't needed.
• CPS and firmware version mismatch — the codeplug reads/writes with corruption.
• No backup of the factory codeplug — later there's nothing to roll back to.

These and another dozen pitfalls, with ready solutions, are collected in our article on common codeplug mistakes — look there at the very first "it doesn't work."

How to set up channels for your own network and hotspot

If you operate on DMRhub, the scheme is extremely simple. From your dashboard you take your DMR ID and the network's talkgroup list, create a digital contact (Group Call) for each group, assemble a "Network" RX Group List, and create channels on your hotspot's frequency with the Color Code and TS2 as described above. On the network side the voice goes through the server's AMBE vocoder, so you don't need a separate hardware dongle — a properly configured radio and hotspot are enough. The ready-made RadioStar image for the Raspberry Pi deploys a hotspot in practically a couple of steps and provisions itself for your account.

Bottom line

The Retevis RT3S is an honest workhorse for getting into DMR, if you don't begrudge an hour on the initial setup. The keys to success are the right cable and a version-matched CPS, a mandatory backup of the factory codeplug, bottom-up assembly (contacts → RX Group List → channels → zones), and a pedantic check of three parameters on every digital channel: frequency, Color Code, and time slot TS2. Do it carefully, and this budget dual-bander will hold your network confidently on par with radios three times the price.