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Zero Retries Guide to VHF / UHF Radios for Data

Compiled by Steve Stroh N8GNJ
Editor - Zero Retries Newsletter

Software Defined Transceivers are out of scope of this Zero Retries Guide.

Frequency references are for US versions. Other countries have different frequency ranges for their VHF / UHF bands. Example - no 222 - 225 MHz band outside US and Canada.

In Production / No Modification Required / Amateur Radio

“In production” generally equates to the radio being listed as available from Ham Radio Outlet (primary reference) or other retail vendor (when I’m able to verify other availability).

This section lists Amateur Radio VHF / UHF FM radios that are known to be usable for high(er) speed “audio interface” data communications such as VARA FM and 9600 bps Frequency Shift Keying (FSK) that do not require modification to be usable for higher speed data.

HF / 50 - 54 MHz / 144 - 148 MHz / 440 - 450 MHz

50 - 54 MHz

  • Alinco DR-06T (Use Adapter 1 for standard 6-pin MiniDIN “data” port)

144 - 148 / 222 - 225 / 440 - 450 MHz

144 - 148 / 440 - 450 MHz

Note on Yaesu FTM series radios - The “flat audio” capability of this series of radios is not mentioned prominently in marketing material, but each unit listed below has been verified to have the Yaesu-standard 10-pin MiniDIN data port as shown in the manual for each unit. The ASP variants of the Yaesu radios listed adds “Audio Signal Processor [to] improve reception of weak signals”. Of the Yaesu radios listed below, all except the FTM-150R incorporate Yaesu’s C4FM digital voice capability, which isn’t used for data communications with an external TNC or audio interface.

144 - 148 / 440 - 450 / 1240 - 1300

  • Icom IC-9700 - no external flat audio connections, but does include an integrated audio interface. Also incorporates Icom D-Star Digital Data (DD) mode - 128 kbps on 1240-1300 MHz.

144 - 148 / 440 - 450 / 1240 - 1300 / 2400 / 5600 MHz

  • Icom IC-905 - no external flat audio connections, but does include an integrated audio interface. Also incorporates Icom D-Star Digital Data (DD) mode - 128 kbps on 1240-1300 MHz.

144 - 148 MHz

  • No 144-148 MHz “data” radios are currently in production that don’t require modification.

222 - 225 MHz

  • No 222-225 MHz “data” radios are currently in production that don’t require modification.

430/440 - 450 MHz

  • No 430/440 - 450 MHz “data” radios are currently in production that don’t require modification.

In Production / Some Modification Required / Amateur Radio

“In production” generally equates to the radio being listed as available from Ham Radio Outlet (primary reference) or other retail vendor (when I’m able to verify other availability).

This section lists Amateur Radio VHF / UHF radios that are in production that are known to be usable for high(er) speed “audio interface” data communications such as VARA FM and 9600 bps Frequency Shift Keying (FSK) but require some modification to be usable for higher speed data. Radios listed in this section have detailed modification instructions available.

TYT TH-9000D

  • TYT TH-9000D, most popularly sold on Amazon. Variant for 144 - 148 MHz.

  • TYT TH-9000D, most popularly sold on Amazon. Variant for 222 - 225 MHz.

  • TYT TH-9000D, most popularly sold on Amazon. Variant for 440 - 450 MHz.

The TYT TH-9000D can be easily modified for (some) flat audio to a 9-pin DSUB socket. Reportedly this series of radios are clones of the Alinco DR-135 / 235 / 435 radios that featured a flat audio connection from a 9-pin DSUB socket.

Note from Masters Communications: [TYT TH-9000] radios are not 9600 or VARA FM Wide capable, but work well with VARA FM Narrow.

See the articles:

TYT TH-9000D Modification Instructions:

TYT TH-9000D Modification Hardware

No Modification Required / Out of Production / Amateur Radio

Amateur Radio VHF / UHF radios that are out of production that are known to be usable for high(er) speed “audio interface” data communications such as VARA FM and 9600 bps Frequency Shift Keying (FSK) that do not require modification to be usable for higher speed data.

Unless otherwise noted, radios in this section have an integral 6-pin MiniDIN “data” port.

28.0 - 29.70 / 50 - 54 / 144 - 148 / 430 - 450 MHz

144 - 148 MHz / 222 - 225 / 440 - 450 MHz

  • Kenwood TH-F6A - Only portable radio that (unmodified) provides flat audio connections. A menu setting switches the microphone / speaker connections to bypass pre-emphasis / de-emphasis circuitry for flat audio. Requires a custom cable for use with a higher speed TNC or audio interface.

144 - 148 MHz / 440 - 450 MHz

  • Kenwood TM-D700 - This was an excellent data radio. While this radio included an internal TNC, the internal TNC could be bypassed for use with external audio interfaces and TNCs. Not only did it include an integral 6-pin Mini DIN “data” port, but its operating modes were remotely controllable via an RS-232 port.

  • Kenwood TM-D710 - This was an excellent data radio. While this radio included an internal TNC, the internal TNC could be bypassed for use with external audio interfaces and TNCs. Not only did it include an integral 6-pin Mini DIN “data” port, but its operating modes were remotely controllable via an RS-232 port.

  • Kenwood TM-V71A - This was an excellent data radio. Not only did it include an integral 6-pin Mini DIN “data” port, but its operating modes were remotely controllable via an RS-232 port.

  • Yaesu FTM-200DR (Use Adapter 3 for standard 6-pin MiniDIN “data” port)

  • Yaesu FTM-300DR (Use Adapter 3 for standard 6-pin MiniDIN “data” port)

  • Yaesu FTM-500DR (Use Adapter 3 for standard 6-pin MiniDIN “data” port)

  • Yaesu FTM-6000R (Use Adapter 3 for standard 6-pin MiniDIN “data” port).

144 - 148 MHz

222 - 225 MHz

440 - 450 MHz

This section in development.

Some Modification Required / Out of Production / Amateur Radio

Amateur Radio VHF / UHF radios that are out of production that are known to be usable for high(er) speed “audio interface” data communications such as VARA FM and 9600 bps Frequency Shift Keying (FSK) but require some modification to be usable for higher speed data. Radios listed in this section have detailed modification instructions available.

144 - 148 MHz

  • Kenwood TM-271 - The European version of this radio includes a DSUB-9 connector for flat audio. The US version of this radio does not include that connector, but the internal connections are accessible and there is a cutout on the back panel for the DSUB-9 connector. Or you can opt to bring out the flat audio signals directly into a 6-pin MiniDIN cable.

    Modification instructions per Arcom:
    Kenwood TM-271 Packet Connector, COS and PL Mod

    Modification instructions per Steven Davidson K3FZT:
    New 2-m Winlink Gateway for Philadelphia Area Hams

    This section in development.

No Modification Required / Out of Production / Commercial

Commercial (surplus) VHF / UHF radios that are out of production that are known to be usable for high(er) speed “audio interface” data communications such as VARA FM and 9600 bps Frequency Shift Keying (FSK). Radios listed in this section do not require modification to access flat audio connections, but do require reprogramming1 for use in Amateur Radio VHF / UHF spectrum.

Radios listed in this section have reprogramming instructions available, but sometimes reprogramming software and hardware is problematic and expensive to acquire for a single radio. W1BTR Big Time Radio offers a Radio Programming Service for commercial radios to Amateur Radio frequencies.

The primary factors to consider a commercial radio that is out of production are low cost (typically exceeded their commercial service life and sold as surplus), rugged and reliable, and simpler for dedicated use such as data links on single frequencies - no or minimal display and controls. There are nearly infinite variations of commercial radios as their configuration and options are often customized for a particular customer. Thus you really need to know how to interpret model numbers and other configuration information such as option codes to be sure what you’re buying.

This section in development.

Some Modification Required / Out of Production / Commercial

Commercial (surplus) VHF / UHF radios that are out of production that are known to be usable for high(er) speed “audio interface” data communications such as VARA FM and 9600 bps Frequency Shift Keying (FSK). Radios listed in this section typically require modification to access flat audio connections.

Radios listed in this section have reprogramming instructions available, but sometimes reprogramming software and hardware is problematic and expensive to acquire for a single radio. W1BTR Big Time Radio offers a Radio Programming Service for commercial radios to Amateur Radio frequencies.

The primary factors to consider a commercial radio that is out of production are low cost (typically exceeded their commercial service life and sold as surplus), rugged and reliable, and simpler for dedicated use such as data links on single frequencies - no or minimal display and controls. There are nearly infinite variations of commercial radios as their configuration and options are often customized for a particular customer. Thus you really need to know how to interpret model numbers and other configuration information such as option codes to be sure what you’re buying.

Radios listed in this section have detailed modification instructions and reprogramming instructions available.

…

This section in development.

Explanation of “Higher Speed” VHF / UHF FM “Data Radios”

Almost any VHF / UHF FM radio can be used for data communication, as evidenced by how widely 1200 bps Audio Frequency Shift Keying (AFSK) packet radio has been implemented, most widely with Automatic Packet Reporting System (APRS).

1200 bps AFSK works well with typical FM radios because its audio tones are well within the audio bandwidth of the radio (designed to convey the frequencies of the human voice). Human voice is conveyed well by FM radios in part due to “pre-emphasis” circuitry in the transmission / microphone section which boosts voice audio for better transmission, and “de-emphasis” circuitry in the receiver / speaker section which removes the boosted audio for clearer receive audio.

However, the pre-emphasis and de-emphasis circuits of VHF / UHF FM radios begin to distort the more complex audio used for higher speed data communications. 2400 bps AFSK is usually possible with most radios using the microphone / speaker connections, and some radios can achieve 4800 bps AFSK. But 9600 Frequency Shift Keying (FSK) has not been made work2 using microphone / speaker connections.

When TAPR, K9NG, and G3RUH co-created the Amateur Radio 9600 bps FSK modem in the mid-1980s for VHF / UHF FM radios, it required that the voice pre-emphasis / de-emphasis circuits be bypassed. Initially, any VHF / UHF FM radio used for 9600 bps FSK had to be individually modified. Methods to bypass pre-emphasis / de-emphasis circuits varied with each radio’s unique circuitry.

Within a few years, manufacturers began offering VHF / UHF radios with a “data” connection - see Explanation of the Amateur Radio 6-pin MiniDIN “data” (9600 port) connector below.

Radios listed on this page (with the exception of Icom Digital Data (DD) Radios and Repeaters, and New Packet Radio sections are VHF / UHF FM radios with voice pre-emphasis and de-emphasis subsystems bypassed. Note that these “data” radios are typical VHF / UHF FM radios in every respect… just with a special connector (and in some cases, mode settings in the radio’s menu) to provide flat audio signals for data use.

While the bypassing of pre-emphasis and de-emphasis technique was developed to use 9600 FSK, the advantages for data communications of that technique has been used with more sophisticated data modes3 such as VARA FM that layer multiple techniques4 to use all available audio bandwidth to achieve speeds up to 25 kbps - more than 2.5 times as fast as the original 9600 bps data rate. Some VHF / UHF FM radios have been specifically designed for even wider bandwidth audio5 and can achieve data rates of 19200 bps FSK, or perhaps even faster.

VARA FM Can Achieve 12.5 kbps Using Microphone / Speaker Connections

Because VARA FM layers multiple techniques to achieve fast data rates, it can adapt to the “constraint” of pre-emphasis / de-emphasis being in the audio path, it can achieve 12.5 kbps even when using the microphone / speaker connections of any VHF / UHF FM radio. It’s a valid argument that when VARA FM is used, a flat audio connection isn’t necessary for “9600 bps equivalent” data speeds.

Explanation of the Amateur Radio 6-pin MiniDIN “data” (9600 port) connector

The standard 6-pin MiniDIN connector on some Amateur Radios is referred to as the “Data” connector. This connector is also referred to as the “9600 port”.

Image from Wikipedia - https://en.wikipedia.org/wiki/9600_port

See the Wikipedia article 9600 port for a basic explanation.

Analog, not Digital
This connector does not provide data (digital) signals (suitable for direct connection to a computer). Signals available on this connector are analog - audio input, audio output, and Push-to-Talk. Signals on this connector have bypassed the radio’s voice pre-emphasis (microphone) and de-emphasis (speaker) circuits so that audio signals from “modems” (sometimes referred to as “TNCs” or “Sound Cards”) will not be distorted by the radio’s pre-emphasis and de-emphasis circuits.

Flat Audio
Audio that is not pre-emphasis and de-emphasis is sometimes referred to as “flat audio”, typically in conjunction with repeaters that use audio conditioning units or circuits.

Originally Used for 9600 bps
This connector was originally used (required) for 9600 bps data using Frequency Shift Keying (FSK). 9600 bps data is rarely used in the past decade, thus the 6-pin MiniDIN connector is usually not included in new Amateur Radios. The development of VARA FM, and its ability to transmit and receive data up to 25 kbps caused a resurgence in interest in radios that included this connector, and some new radios, such as the recently introduced radios from Yaesu, include this connector.

This section in development.

Adapters for Standard 6-pin MiniDIN “Data” Connector

Adapter 1 (Alinco)
Masters Communications Model Alinco-6 adapter converts the DSUB-9 connector used on Alinco DRx35 series radios to standard 6-pin MiniDIN.

Adapter 2 (Bridgecom)
Masters Communications BCM-6 adapter converts the unique High Density DSUB-15 connector used on Bridgecom BCM-xxd radios to standard 6-Pin MiniDIN.

Adapter 3 (Yaesu)
Masters Communications DIN6-164 cable converts the unique 10-pin MiniDIN connector used on some Yaesu radios to standard 6-pin MiniDIN.

Yaesu CT-164 converts the unique 10-pin MiniDIN connector used on some Yaesu radios to standard 6-pin MiniDIN.

Adapter 4 (Kenwood commercial)

Masters Communications Model Kenwood-25 Adapter converts the DSUB-25 connector used on some Kenwood TK-x90 radios to standard 6-pin MiniDIN.

Adapter 5 (Motorola)

Masters Communications Model Motorola-16 Adapter converts the 16 pin (or 20 pin) accessory (option) jack used on some Motorola radios to standard 6-pin MiniDIN.

RPC Electronics Motorola 16 Pin MiniDIN Packet Adapter converts the 16 pin accessory (option) jack used on some Motorola radios to standard 6-pin MiniDIN.

This section in development.

Masters Communications Model FMDM-150M FM Deviation Meter

For as long as we’re going to be using FM transceivers for data communications, connecting external audio adapters, TNCs, modems, etc. to FM transceivers, setting correct Deviation is a significant issue for optimum performance.

Thus the FMDM-150M is a notable accomplishment in the service of data communications (using FM radios) over Amateur Radio - kudos to Kevin Custer W3KKC of Masters Communications for creating this unit.

While setting “good enough” deviation “by ear” is usually possible for lower speed data modes like 1200 bps Audio Frequency Shift Keying, higher speed data modes suffer when deviation isn’t set correctly. I purchased an AEA DM-1 at a hamfest last year mostly because it was cheap. I remember its reputation at the time it was introduced was “better than nothing” and it was an appliance rather than a big, expensive, hard to use service monitor.

Thus this low cost unit for determining accurate deviation with the interesting approach of using a Uniden BC335N scanner (with a minor modification) as the receiver system.

While individual might now want to invest in this system to set up a few personal data radios, this would be an ideal investment for an Amateur Radio club interested in data communications, or just a group of friends who want to do data communications.

Other Compilations of Radios Suitable for Data

This section in development.

Icom Digital Data (DD) Radios and Repeaters

Icom Digital Data (DD) mode is a feature of some Icom radios and repeaters. It provides data speeds of 128 kbps using a 100 kHz channel on 1240 - 1300 MHz.

This section in development.

New Packet Radio

New Packet Radio (despite its name) has no relation to conventional Amateur Radio Packet Radio. It is a new, unique, TCP/IP-based data protocol for Amateur Radio data communications. It provides data speeds up to 512 kbps using a 100 kHz channel on 430 - 450 MHz.

This section in development.

Change Log:

  • 2026-01-16

    • Added Masters Communications Model FMDM-150M FM Deviation Meter

  • 2026-01-13

    • My thanks to the discussion on the Zero Retries email list about this Zero Retries Guide with many helpful suggestions.

    • Corrected duplication of Adapter 1 and Adapter 4

    • Updated guidance verbiage in Commercial sections.

    • Added to Kenwood TM-271:

      • Modification instructions per Steven Davidson K3FZT:

        New 2-m Winlink Gateway for Philadelphia Area Hams

    • Added to No Modification Required / Out of Production / Amateur Radio:

      • Azden PCS-9600D

    • Added to No Modification Required / Out of Production / Commercial:

      • Kenwood TK-x90 Series Radios

      • Motorola CDM Radios

      • Tait FM Radios

    • Added to Adapters for Standard 6-pin MiniDIN “Data” Connector:

      • Adapter 4

      • Adapter 5

  • 2026-01-12

    • My thanks to the discussion on the Zero Retries email list about this Zero Retries Guide with many helpful suggestions.

    • Reordered some information.

    • Added to In Production / No Modification Required / Amateur Radio:

      • Icom IC-7100

      • Icom IC-905

      • Icom IC-9700

    • Added to No Modification Required / Out of Production / Amateur Radio:

      • Yaesu FT-8900R

      • Kenwood TH-F6A

      • Alinco DR-135TMKIII

      • Alinco DR-235TMKIII

      • Alinco DR-435TMKIII

      • Kenwood TH-F6A

      • Yaesu FT-8900R

    • Added to Some Modification Required / Out of Production / Amateur Radio:

      • Kenwood TM-271

    • Added to Icom Digital Data (DD) Radios and Repeaters:

      • Icom IC-905

      • Icom IC-9700

      • Icom ID-1

      • Icom ID-RP1200VD Repeater

    • Added new section:

      • Explanation of “Higher Speed” VHF / UHF FM “Data Radios”

    • Added several footnotes.

  • 2026-01-11

    • My thanks to the discussion on the Zero Retries email list about this Zero Retries Guide with many helpful suggestions.

    • Added to In Production / No Modification Required / Amateur Radio:

      • Yaesu FTM-310DR

      • Yaesu FTM-310DRASP

      • Yaesu FTM-510DR

      • Yaesu FTM-510DRASP

    • Added verbiage to In Production / No Modification Required / Amateur Radio about new Yaesu radios.

  • 2026-01-06

    • Added to In Production / No Modification Required / Amateur Radio:

      • Yaesu FTM-150R

    • Added to Out of Production, No Modification Required / Amateur Radio:

      • Kenwood TM-D700

      • Kenwood TM-D710

    • Added verbiage:
      “In production” generally equates to the radio being listed as available from Ham Radio Outlet (primary reference) or other retail vendor (when I’m able to verify other availability).

    • Deprecated from In Production, No Modification Required / Amateur Radio… to Not in Production, No Modification Required / Amateur Radio:

      • Bridgecom BCM-220

      • Yaesu FTM-200DR

      • Yaesu FTM-300DR

      • Yaesu FTM-500DR

      • Yaesu FTM-6000R

  • 2024-12-13

    • Added to In Production, No Modification Required / Amateur Radio:

      • Yaesu FTM-150RASP

    • Added Masters Communications DIN6-164 Cable

    • Deprecated from In Production, No Modification Required / Amateur Radio… to Not in Production, No Modification Required / Amateur Radio:

      • Bridgecom BCM-144

      • Bridgecom BCM-440

  • 2024-08-30:

    • Added to In Production / Some Modification Required / Amateur Radio:

      • TYT TH-9000D

1

Reprogramming using software; radios that require crystals are out of scope.

2

Amateur Radio Operators in Japan adapted fax technology to achieve 9600 bps (and faster?) using microphone and speaker connections. However, each transmission required long training times for the “fax modem” to “sound out” the audio path. While this approach did work, especially when long transmissions were used such as file transfers, it was not widely used outside of Japan. The “modify the radio for flat audio connections” for use with 9600 and faster data communications was much more widely used.

3

Using the compute resources of a modern computer with multiple cores / GHz clock speeds, and Gigabits of RAM…

4

Description of the multiple techniques used by VARA FM is out of scope of this Zero Retries Guide, but another Zero Retries Guide that discusses VARA FM (and VARA HF) is in development.

5

Not yet listed in this guide.

© 2026 Steve Stroh N8GNJ · Privacy ∙ Terms ∙ Collection notice
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