Retevis RT98 for APRS, review 8 weeks after

After almost 8 weeks of using this little radio for my mobile APRS operations I thought it’s a good time to provide some feedback. I must admit I have mixed feelings about this radio…

I bought the radio because it was cheap and compact, almost as big as the Tinytrak 4! While investigating on how I could hook the Tinytrak to it I found out there is an unsquelched audio output. Unsquelched means the received audio signal is available regardless of the squelch setting or configured CTCSS tone! But I’ll come back to this point later.

While the RF part seems to be well conceived and built, the software part has some quirks

The RT98 seems to have a well built RF part. It has a very clean and sensitive receiver: while mobile and moving on a small hill I can directly pick up APRS data from Switzerland about 150km away. The transmitter too seems to be well built. My TH-9000 used to wipe out the reception on the FM car radio when sending out an APRS frame. This does not happen with the RT98.

While the RF part seems to be well conceived and built, the software part has some quirks. First, the absolute non-sense of removing the VFO functionality makes it absolutely useless for regular ham rag chew usage, but is fine for APRS where you are unlikely to change frequency. There is a V/M key which, in previous versions of the radio, allowed you to switch from memory mode to VFO. On this radio, it only cycles through different display modes : frequency, memory name and memory name + memory number.

The RT98 in my trunk with the Tinytrak 4

When leaving the settings menu at a specific setting entry and going back into the menu you’d expect to be at the menu point you were before. No, you start right at the first setting, annoying.

Since I am using the radio for APRS I like the keys and other commands to be locked to avoid unintentional changes. Well lock the radio, turn of the power (the radio is powered through ignition key) turn the radio on : it is unlocked…. Useless…

As I wrote earlier, the point inside the radio where I tap the receive audio is totally unsquelched i.e. the received audio is present regardless of the squelch setting or CTCSS. This makes it perfect for Voice Alert. The radio’s speaker is muted, the Tinytrak happily decodes the APRS frames in the background and the speaker opens as soon as a matching tone is received. How naive I was.

The CTCSS handling must have been implemented by a trainee I guess. As soon as you enable CTCSS, the radio exhibits a whopping 250ms long TX tail. Release the PTT and the radio still transmits silence with CTCSS tone for 250ms. This will make you miss any APRS packet within this time frame plus it will congest the network unnecessarily as other modems will not detect any digital carrier they will determine the frequency is clear and transmit… Boom collision….

The radio is quite usable for APRS as long as you give up on Voice Alert

I know that I like to over emphasize things in my writings and might give the impression to think the radio is crap. Yet I have to admit the radio is quite usable for APRS as long as you give up on Voice Alert, it is compact, cheap and quite well built. I would definitely recommend it over a mobile Baofeng on steroids (Baojie, QYT and similar).

I am still in the market to find a capable radio where I could do Voice Alert. I will most probably recycle the RT98 in a digipeater project. I have a Kenwood TM-251E, waiting for the DSU-8 CTCSSS board to arrive to give it a try…

To be continued….

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