Salvage, Teardown: DingTong DT-98 8W 403-470Mhz Handheld Transceiver

Imagine my surprise when stopping to catch the bus one day, I see a hand-held radio in the grass not far from the bus stop. I was in a hurry and had to leave, so I hopped on the bus and forgot about it.

The next day, I was catching the bus again, and the unit was still there. Figuring it was probably lost and unwanted, I examined the unit but was unable to determine to whom it belonged. It was dead, with no identifying markers on it. It was also fairly dinged up, as if it had case damage from being thrown out of a speeding car, and then possibly run over, flinging it up from the road into the grass.

No matter the case, it was a Chinese import radio, of the sort that ACMA looks scornfully on. So I suppose maybe it was a good thing the owner threw it out the window, otherwise they might be liable for a fine. But this does give me a chance to examine one, so I took it home and took it apart.

The Unit

The unit is a DingTong branded unit, of a most basic design similar to the BaoFeng BF-888S, possessing no LCD display whatsoever. The unit has a short whip antenna, with front speaker, mic and LED indicator. There is a belt clip on the rear with cradle charging contacts, and both sides show damage from skidding across the road.

The discarded unit had no volume control knob, presumably lost in the impact. Like many Chinese import radios, the polarity of the SMA connector is reversed – male on the unit and female on the antenna. The whip is marked for 400-470Mhz operation, gain is unknown but not presumed to be high.

The left side has the PTT, and two other buttons, presumably monitor and (possibly) power level/light/something else.

 

The right side has a pair of jacks used for a remote headset/earpiece.

Removing the belt-clip and battery shows that it is a DingTong DT-98, claiming 8W of power output and a frequency range of 403-470Mhz. The URL listed does not lead to the manufacturers’ site (instead, to some advertising).

On Trial

The unit was practically dead on arrival. This is not unexpected, as it was left powered up on Channel 16 since its abandonment. As a result, to see what it could do, I had to give the battery a little charge first. A quick trip to my benchtop supply and that was enough to get it started.

As part of being a low-cost no-frills radio, it has no LCD at all. As a result, it relies on a rotary selector dial with markings. But as this can get hard to read with 16 positions in all, the unit also has voice synthesis which announces the channel numbers in mandarin (which sounds like this). The unit pops loudly at every frequency change, so it’s probably not very good with an earpiece.

I was interested to know who might have used the unit and how they were using it, so I hooked the antenna output through some adapters to a dummy load to give it a quick test on all 16 programmed channels. A small amount of leakage from the dummy load would ensure that nobody would be adversely interfered with, along with being short 2-second burst transmissions. The leakage was sufficient for my old radio scanner in frequency counter mode to register the frequencies.

These were (in Mhz):

1. 430.025
2. 431.025
3. 432.025
4. 433.025
5. 434.025
6. 435.025
7. 436.025
8. 437.025
9. 438.025
10. 439.025
11. 439.125
12. 439.225
13. 439.325
14. 439.425
15. 439.525
16. 439.625

A quick check of the frequencies seems to show a pattern which may be used for factory alignment, so it seems this radio was never programmed. This seems to be a radio sold by people who may not know much about radios as “walkie talkies” on the premise of “select-a-channel and it works”. But unfortunately, the frequencies that they come programmed with can cause trouble – they could overlap with licensed users and cause interference.

For one, the frequencies chosen do not seem to align with any known “CB style” service. It’s not:

  • Australian UHF CB (476-477Mhz)
  • “Public radio service” in China (409Mhz)
  • SLPR (420-422Mhz) as used in Japan
  • UHF-FM (448-449Mhz) as used in South Korea
  • FRS/GMRS (462/467Mhz) as used in the USA
  • PMR446 (446Mhz) as used in Europe.

Instead, they are in the 70cm Amateur Radio band (430Mhz – 450Mhz) with some overlap with the 433-434Mhz LIPD devices. Based on an ACMA Radcomms database search, and a look in the WIA bandplans, the channels are used by the following in the Sydney/NSW area:

  1. Hornsby and District Amateur Radio Club Repeater Input (VK2RHT)
  2. Amateur Repeater Input (although none in NSW at this time)
  3. Earth-Moon-Earth Frequency Band
  4. Hunter Radio Group Repeater Input (VK2RNC)
  5. Goulburn & Southern Highlands Amateur Radio Society Repeater Input (VK2RHR)
  6. Amateur Satellite Band
  7. Amateur Satellite Band
  8. Amateur Satellite Band
  9. Goulburn & Southern Highlands Amateur Radio Society Repeater Output (VK2RHR)
  10. Amateur Simplex
  11. Hornsby Packet Radio Repeater (VK2RPH)
  12. Amateur Simplex
  13. Hellenic Amateur Radio Association of Australia Repeater Output (VK2RSV)
  14. Chifley Amateur Radio Club Repeater Input (VK2RCZ)
  15. WICEN Repeater Output (VK2RAV)
  16. WICEN Repeater Output (VK2RFI)

Looking at the channels, a good number of them are over repeater inputs which could cause them to key-up and rebroadcast the signal further than expected. Without the offset programmed into the radio, the user would not be aware that they’re perhaps being rebroadcasted over a wide range, and the people trying to “tell them off” would not be heard by the user. Of course, this is quite a notable issue with amateur radio repeaters, so many have CTCSS tone squelching on their inputs. While this stops them from being rebroadcast, their transmissions will still cause blocking and interference of legitimate transmissions and potentially an annoying heterodyne squeal.

Some of the channels are over repeater outputs. This is probably not as bad comparatively speaking, but will mean that they may hear some signals they’re not expecting to hear, and their transmissions may jam some legitimate users from hearing the output of the repeater (depending on the relative strength of the signal). With 8W to play with, this radio probably will put out a stronger signal than the average hand-held, but I suppose the antenna’s probably not too great either.

The remaining channels are a little more complex. Channel 3 in the Earth-Moon-Earth frequency band and Channels 6-8 in the Amateur Satellite Band are specially reserved regions of the bandplan as these services to space can require working very weak signals, and thus having the minimum of noise and interference is necessary. Sending out a strong terrestrial signal, when we’re trying to receive a space-borne signal which is very weak, is surely going to ruin the day. There is a potential that it could jam a satellite’s uplink frequency as well, denying service to a wide-footprint simultaneously (as the satellite has a large field of view which could span across states/countries).

Of all the channels, Channel 10 and 12 are probably the most innocuous of the bunch, as they are intended for simplex working. However, one must remember that to use the amateur radio bands, they must be appropriately licensed, pay the fees and identify by callsign at the required intervals.

At least the unit did not broadcast on the government band (roughly 410 to 430Mhz, using APCO25) or it could endanger lives by jamming first-line responder’s digital radios in an inconsistent and intermittent way (as analog signals jamming a digital transmission would not be decoded by the intended radio, and APCO25 trunking may cycle the frequencies from transmission to transmission, so only some transmissions are garbled). This probably explains the strong stance ACMA has against “Chinese import” radios, while understandable to some degree, is also confusing for some radio amateurs who are fully aware of the rules, have the tools to program radios appropriately and use them responsibly, and see that the radios are otherwise not causing significant issues in terms of spurious emissions.

I did take a look around for some programming software, but I couldn’t find any. The manufacturer’s website just leads to some advertising, a search online showed absolutely nothing. As a guess, it could be based upon the Baofeng or Woxun models, so I grabbed a standard Baofeng style programming lead and cycled through every radio supported by CHIP, but to no avail. The radio would not be read-out when it was powered on, or powered off.

As a result, given the frequencies it was already on and the damage it had suffered, I decided to take it apart and dispose of it.

Teardown

To take it apart, two Torx screws at the bottom need to be undone, and then the collars which hold the pots and SMA socket in place need to be undone and removed. Then, the whole rear assembly pops out, bottom first, similar to some Motorola radios.

We can see that all costs have been optimised, and the speaker (of a 16 ohm 1W rating) is glued into the case and soldered to the board. To take it apart more gracefully, I got out my soldering iron and desoldered the wires. The electret microphone is covered with a rubber boot which insulates against feedback, and this is “pressed into” by a channel in the front case – this has eaten into the rubber and damaged it. Apparently this radio was inspected by “QC04”.

The silkscreening is marked GLW-1, with a PCB date of Week 13 of 2017, making this a very recent unit. Components on this side include the electret microphone for use hand-held (although crushed somewhat by the case), a JRC NJM2904 dual-opamp and an RDA5802N FM stereo radio tuner. There is also a trimmer, which is probably used to align the frequency, conveniently placed on this side.

To remove the PCB to examine the other side, a large number of screws have to be undone, but also, the centre pin of the SMA jack needs to be desoldered to let the board come free of the metal casing.

The casing itself seems to be cast with channels and areas acting as both heatsink and shielding. Some of the work to do with the casting appears manually done – note the “B” marked into the mould. The rear battery clip mechanism is attached to the plastic at the top by two screws.

This is merely a plastic hook that is free to slide, with a spring providing the force to “return” it to the home position. It pushes against the channel cut into the metal casing.

The bulk of the components are on the other side, but surprisingly, the number of components is less than I expected, because of the use of mixed-signal IC technology. One of the transistors had thermal paste and a thermal pad to allow for heat conduction to the metal rear.

The bottom left corner appears to be the frequency reference crystal and modulator/demodulator section. This makes sense as the crystal oscillator is situated there, along with the tuning adjustment pot on the rear. The main chip is marked AT1846S and is an integrated single-chip transceiver based on DSP techniques in a CMOS technology chip. It has an analog IQ baseband interface, and supports a number of frequency bands and features such as AFC, AGC, emphasis/de-emphasis, RSSI, VOX, SQ, CTCSS/DCS encode/decode, DTMF, volume control and sleep modes. It has 8 GPIOs and an I2C control interface.

As a result, it seems that the control is taken care of by the left-top portion of the image, with a HM AP88F389 (unknown) microcontroller, with some ATMEL 24C08AN EEPROM for configuration data. The chip marked VOICE-D is probably the voice synthesis chip. I did try desoldering the EEPROM to read-out on my programmer, but I must have damaged it somehow as it was a dead short. There is also a MC34119L audio amplifier IC to drive the speaker.

The lower half of the board, towards the right, appears to be the RF front end filters and amplifier, hence the transistor with the thermal paste. This makes sense as it’s next to the transceiver chip, which only has an output of 8dBm (or about 6.3mW) and the radio claims an 8W output.

Testing the Battery

As I have taken the whole unit apart, I decided to take the battery apart too. Its rating is a very curious 7.4V 3000mAh, which seems too unrealistic for the size.

I was interested to see whether they used Li-Ion or Li-Poly cells as well. After all the physical trauma they’ve been through, I don’t think I want to keep it around for too long, just in case they suffer some “delayed” spontaneous combustion.

The cell is glued together at the seams, and it was a destructive process to pry it apart. Unexpectedly, it seems that the protection board is at the bottom of the battery, so there are long tabs that connect the terminals at the rear of the battery to this board. Because of their close proximity to each other, one wrong move and you have a short circuit. The construction also needs a soldering iron to deconstruct neatly.

A closer look at the bottom shows that the rear “T” thermistor contact on the outside is an absolute lie. There is no pack thermal monitoring, and thus the charger cradle itself might not even have circuitry that expects to use it. They probably included it just to “look safe”.

The end PCB is quite simple with two intermediate series contacts marked I-I on the left, and the battery pack + and – marked B+ and B- on the right. The charger input comes in through the Z+ and Z- terminals, and the power to the radio is supplied through the P+ and P- terminals.

The underside of the board is noticeably bare. It’s marked ChaoNian 885EF, and has just a single 8205A transistor package and a 6-pin IC. I wonder if this is a protection IC only, or a balancing IC only, or both. Regardless, it is lacking any form of secondary safeties, making it quite a questionable design.

Each cell is a prismatic Li-Ion cell with a thin metal shell. Terminals are spot-welded to the same end with cardboard insulation and blue shrink-wrap around the cells. Green insulating paper is wrapped around the assembly.

Each cell is marked KY483760 201703YX. I presume this means the cells were made in March 2017 by a company with the initials YX or KY, although more information could not be found.

For testing, I topped off each cell individually on my Keysight E36103A bench-top supply to 4.2V (CV) at 300mA (CC) until the current fell to 50mA. Then the discharge was run at 300mA (CC) until 2.8V on the B&K Precision Model 8600 DC Electronic Load.

As we can see, it seems that each of the cells tested at about 1300mAh. As a result, each of the cells being about 1500mAh is a possibility, as often the cells “settle” to between 80-90% of the rated capacity for the majority of their life. However, the claim that it is 7.4V 3000mAh is just patently wrong – when the cells are used in series, the voltages add but the capacity does not. As a result, it’s truly a 7.4V 1305mAh battery as tested.

Conclusion

The DingTong DT-98 seems to be quite an “anonymous” Chinese import radio. This unit seems to be a rather recent unit judging from the date codes, and didn’t live a long life before it was “discarded” by the roadside. Despite this, information about the unit appears to be sparse and the manufacturer’s website is non-existent. I could not find any compatible programming software for it either.

While I didn’t test it for its spectral output or audio quality, I did see that the unit appeared to be unprogrammed and using a set of frequencies which resided in the 70cm amateur band. While this is not the worst outcome possible, it still poses a decent potential for interfering with amateur radio users. The general public and unknowing sellers who just buy and sell the units thinking they are walkie-talkies will be operating unlicensed and liable to a fine as well.

The radio uses the “latest” integrated DSP-based circuitry, and as a result, is much less complex than I expected. There is not much to tweak or align, or even repair. The performance might well leave something to be desired – judging from the rabid arguments that have gone on in regards to other Chinese import radios that have been posted online.

The battery is, in true Chinese fashion, overstated for capacity and relatively “lightweight” on safety features. While I don’t have the charger, I would suspect the safety of the charger may well be questionable as well. The longevity of either is not something I can accurately judge, but at a guess, I’d have to say it’s probably somewhat limited.

As a result, I’d have to say if you don’t know what you’re doing, stay away from these Chinese import radios. You don’t want to be responsible for jamming other paid license users who are conducting business, doing research, or possibly even saving lives (e.g. fire brigade, ambulance). Doing so can come with severe penalties if caught, and is downright irresponsible.

If you must play with the radios, educate yourself about the frequencies you’re allowed to use and then program the units accordingly. Don’t just use them out of the box.

While ACMA is very strict about what units comply with CB, of which none of these Chinese imports generally do, they’re a little less restrictive about amateur radio as the point of it is to research and experiment. That being said, owing to the open-ness of these radios for band-extension and almost any-frequency operation, I can understand their objection to these radios including some blanket statements which make it seem like it’s illegal to even possess them.

That being said, I don’t agree they should be illegal. As long as they’re being used responsibly (on frequency with no significant spurious emissions, transmitting at or below the legal power, following operation protocol), I don’t see what harm they would cause. That being said, it seems unlikely that ACMA will let anyone other than Standard/Advanced radio amateurs will be permitted to use them (even if they are allowed, which is slightly unclear at this stage). A Foundation call person like myself is limited to commercially produced amateur radio transceivers … so unfortunately, the people who might need low-cost handhelds the most are not allowed to use them.

I suppose that’s probably a good reason to take the test and upgrade my license … but at least, for now, the scourge of this DingTong DT-98 has come to an end.

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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5 Responses to Salvage, Teardown: DingTong DT-98 8W 403-470Mhz Handheld Transceiver

  1. Mark says:

    According to the Web Archive, suotom.com once used to be the website of a MP3 player manufacturer: http://web.archive.org/web/20110406042647/http://suotom.com/.

  2. Jimmy Tomson says:

    I know you are done with that radio…
    Chirp works on a lot of radios:
    https://chirp.danplanet.com/projects/chirp/wiki/Home

    • lui_gough says:

      Indeed, as I wrote in the article, I tried a BaoFeng style lead with the unit switched on or off and with every single radio supported by CHIRP at the time (I was using the daily build) and none of them could read out the memory. As per CHIRP instructions, one should not program from a blank slate, and instead need to read-out the data first, modify, then write or risk bricking the radio.

      – Gough

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