Feb 172022

Lately, I’ve been stuck at home with not much bicycle mobile operation happening, and it’s given me time to review where I’m going with the station and the onboard communications systems.

At home, I’ve been listening to a lot of commercial radio, whereas on the bicycle, in pre-COVID times I was basically restricted to recorded music unless I wanted to use the FT-897D for broadcast radio reception.

Now, the Yaesu rig actually isn’t a bad receiver for broadcast radio… but a few downsides:

  • Wideband FM sounds good, but is only received in mono
  • Medium wave and shortwave broadcast requires a rather bulky HF antenna to be deployed
  • The FT-897D is thirsty for power: about 1A on receive
  • When receiving broadcast radio, I obviously cannot monitor amateur frequencies
  • Some of the stations I like listening to are on DAB+, which the FT-897D will never receive

Long-term plan

Long term, the plan is to use SDR to augment the FT-897D, basically I rig up a Raspberry Pi 4 (already procured) with a SDR, and through some antenna switching, basically use the FT-897D as the transmitter with the Raspberry Pi 4 implementing an all-band scanning receiver. That would give me dual-watch (actually, I could watch entire bands) capability which I miss on the FT-897D.

Likely, the SDR chosen will either be a multi-channel one so I can watch a couple of bands: 2m + 70cm; or maybe I monitor 2m whilst listening to a radio broadcast on the other. SDR would also open up DAB+ to me.

This is a long-way off though. And also is rather fixed to the bike, I can’t take any of this stuff on a walk, which lately in COVID times has been my more likely form of exercise.

Current MW rig

For medium wave reception, I do have a small portable transistor radio, a Sanyo BC-088 which I was given years ago in non-working condition. The fault at first was broken PCB traces from the unit being thrown against a wall by its previous owner, which was fixed and allowed the radio to give many years of entertainment for over a decade until another incident on the bike smacked it against Waterworks Road, breaking a few connections to the internal loop-stick antenna.

I’ve repaired that, and the unit now works, but found it does not get along with any microprocessor-based device; picking up all manner of hash when placed near my handheld GPS (Garmin Rino 650) and squealing like a banshee next to my desktop PC. It also seems to be a tad deaf.

SDR is one possible option, but the SDRs I have in my possession: a couple of RTL-SDR v3 dongles and a HackRF One, none of them will tune down to 693kHz where I normally have the BC-088 tuned. The HackRF One gets close at 1MHz, but anything below 10MHz sounds terrible with noise and birdies galore. Even for shortwave, the HackRF One seems to suffer; trying it out on the HF antenna at home, I find myself picking up 4BH at 18883kHz — they normally broadcast at 882kHz.

Thus, I figured I’d try a couple of off-the-shelf options for the short-term and see how they go. Ideally I wanted a single radio that could do MW, FM and DAB+ bands… bonus points if it could do shortwave too.

New DAB+ rig: Digitech AR-1690

I bought this at a time when I noticed all the Australian Radio Network stations (4KQ, 97.3) suddenly go mute on the Brisbane channel 9A multiplex. I wasn’t sure if it was my end or the station, as other DAB+ stations seemed to be fine, and thought this little rig would both be a useful observer, and scratch that itch of portable listening.

The Digitech AR-1690

This is a basic entry-level DAB+/FM set. It’s a smallish unit, roughly 125mm×73mm×30mm. There’s no real special features of this unit. It has 40 station presets; 20 each for FM and DAB+, and there’s two alarm functions that can be set. The clock is set by the radio transmitter time broadcast. The front panel features the volume and channel buttons, along with a SELECT button. The rest of the controls are on the top.

Top controls
  • Info/Menu button:
    • Long-press → enters a configuration menu where you can configure the system time, set the two alarms, see the firmware version or do a factory reset
    • Short press → scrolls through different pieces of information on the LCD display:
      • Frequency
      • Current time
      • Current date
      • (DAB+): Signal strength?
      • (DAB+): Genre
      • (DAB+): DAB+ Multiplex name
      • (DAB+): Frequency and channel
      • (DAB+): Signal error rate
      • (DAB+): Bit rate and standard (DAB or DAB+)
      • (FM RDS): Station name
      • (FM RDS): Genre
  • Mode: Switches between FM and DAB+ mode
  • Scan: Initiates a scan on the currently selected mode (so, all FM broadcast, or all DAB+ channels)
  • Alarm: A shortcut button for setting the alarms (same as holding Info/Menu, then navigating to Alarms)
  • Preset: Used for accessing memory presets, short press recalls a preset, long press to store a station preset
  • Power: Switches the radio on, stand-by (short press) or off (long press)

For power, it can either run on 3 AAA cells, or you can buy separately a Nokia BL-5C Lithium battery.

The back of the radio, nothing much to see here.
The battery compartment, with Nokia BL-5C installed

As for ports, there’s just the two on the right-hand side:


The power jack is a small ~3mm barrel jack, the radio is supplied with a USB cable that interfaces to this connector. Looks like a dead ringer for the old Nokia phone connectors, I might dig up one of my old chargers and see if it works. (Update 2022-03-11: Found one, it doesn’t… the barrel is the same size but the tip in the radio is too big to fit in the bore of the connector.)

In operation

The set seems to do a reasonable job. I’m close to Mt. Coot-tha, so receiving DAB+ really isn’t that difficult. The sound is quite reasonable for the size, I thought the speaker would be a bit on the tinny side, but it’s perfectly listen-able. Certainly it’s a big improvement on the BC-088!

One gripe I do have with this set is that the volume steps are very coarse, and there’s no real “quiet” setting. Minimum volume is mute, one step up is comfortable listening level in a small room. I would have liked maybe 3 or four steps in between.

In both DAB+ mode, it can report the station dynamic labels.

DAB+ dynamic labels

It also can pull a similar stunt with RDS data on FM:

FM RDS reception

New Short wave rig: Tecsun PL-398MP

Now, when I bought the above DAB+ receiver, I ideally wanted something that would do MW broadcast as well, as one of the stations pictured on the DAB set is in fact, a MW station as well.

There is such a beast, Sangean make the DPR-45 which can do MW/FM and DAB+, but it’s enormous. Too big for my needs. Plus I found it after purchasing the little AR-1690 (not that it mattered, as size pretty much rules the DPR-45 out). I figured the next best thing was to get a portable set that had a line-in feature so it could provide the stereo speakers that the AR-1690 lacks.

Enter the Tecsun PL-398MP.

The Tecsun PL-398MP

As the text above the screen suggests, this is quad-band radio; supporting LW/MW/SW and FM bands, as well as a (primitive!) MP3 player. Unlike the Sanyo BC-088 it’s replacing, which boasted 8 transistors (wow!), this unit is a DSP-based receiver using the common Silicon Labs Si4734 radio receiver IC.

Most of the controls are on the front. The labels marked in red are activated when the radio is turned off; so holding 1 down allows you to switch the FM radio band from the default 88-108MHz to 64-108MHz or 76-108MHz. Holding 2 down switches the clock between 12-hour and 24-hour time, 3 will switch the MW band between using 9kHz steps and 10kHz steps, 0 turns keypad beep on/off and the ST button toggles the “intelligent backlight”.

Unlike the AR-1690, this thing runs on either standard disposable dry-cells, or you can install Ni-MH cells and by holding the M button whilst the radio is turned off, you can enable a built-in charger. Dry cells are not exactly my favourite way of powering a device, for no other reason than the reduced energy density and their nasty habit of leaking electrolyte.

Maybe a future project will be to hack a LiPo cell into this thing.

On the back, are the controls for the MP3 player.

Back of the PL-398MP

I’ll get to the MP3 player part in a moment, but in short, don’t bother!

For tuning and volume, there are two thumbwheels on the right-hand side. These are both rotary encoders driving a small microcontroller inside.

Volume and tuning controls

The “digital” volume control steps aren’t too bad for resolution, certainly nowhere near as coarse as the AR-1690! The tuning knob works well enough for small adjustments, and for moving between presets. Thankfully for moving between stations, there’s the keypad for entering frequencies directly.

On the left are all the ports:

FM/SW antenna, line-in, earphone output, and a 5V mini-USB input

The line-in feature is what set this apart from other MW and SW-capable sets. Being able to connect an external shortwave antenna is a welcome feature, and with this radio, I purchased a Sangean ANT-60 antenna for this purpose.

On top, there’s just the Light/Snooze button; pressing it momentarily turns the lighting on. I presume it’ll also silence the wake-up alarm if you have one set, but I haven’t tried this.

Light / Snooze button on top

In operation

FM Stereo reception

I’m close to the Mt Coot-tha transmitter site, so this isn’t much of a strain for the receiver, I guess I’ll know more when I take it out of town with me, but it seems to receive the local stations well, without getting overloaded from the strong ones (looking at you ABC Classic FM).

Being a dual-speaker device, this can provide stereo without additional hardware. Audio quality is actually decent for a radio this size. The speaker drivers are about 50mm in diameter, appear to be a low-profile mylar construction; not going to win audiophile magazine awards and are outperformed by many Bluetooth speakers, but are decent enough.

Short wave reception

The shortwave feature of this set seems good so far. There’s not as much to listen to on the shortwave bands as there used to be, but I’ve been able to receive China Radio International and Radio New Zealand both quite clearly, and one evening managed to pick up the BBC World service.

It performs decently with its built-in antenna, even without me telescoping it out. I haven’t had a chance to fully try the set with the ANT-60 — I did try it indoors in my room, but I suspect I haven’t really got enough wire “in the air” to make much difference. I’ll have to try it at a camp site some evening.

Medium wave reception

This blew me away actually. Okay, so maybe a late 60’s era transistor radio with leaky vintage germanium transistors that’s had a hard life and more than one ham-fisted repair attempt is not much of a contest, but it left the old Sanyo in the dust.

4KQ on 693kHz was a bit of a fiddle to get tuned on the Sanyo, and even then, I found I had to have the radio oriented right to receive it. 4QR on 612kHz of course, was loud and strong. Both stations are very clear on the PL-398MP. Ohh, and while this set’s no rich console radio, it’s nowhere near as tinny as what I was expecting to hear. For a portable rig, quite acceptable.

Out of the box, my unit used 9kHz frequency steps, which will also suit Europe. For those in the USA, you’ll want to hold that “3” button with the power off to switch the radio to a 10kHz spacing. This will also switch the temperature display to show °F instead of °C.

Long wave reception

Firstly, to even get at LW took a bit of fiddling. The handbook is a little inaccurate, telling you to press a non-existent MW/LW button. The correct procedure to enable LW is to turn the radio off, then long-press the AM button. The display will then show “LW” and “On” to indicate the feature is now enabled.

Turning on LW mode.

The same procedure turns the LW feature off too.

Having done so, when you turn the radio back on, pressing the AM button momentarily will now switch between MW and LW.

Now, ITU region 3 where I am, does not have any official LW stations. Nor does region 2 (Americas), this is a feature that’s more useful to those in Europe.

There used to be a LW weather beacon on 359kHz broadcasting out of Amberley Air base, and my Sony ST-2950F (my very first LW-capable receiver) could pick it up with its loop-stick antenna. Neither it, nor the PL398-MP do today. I guess I could drag out one of my amateur sets out to get a third opinion, but smart money is that the transmitter is now turned off.

Never mind, I’ll just turn LW back off and not worry about it.

Line-in feature

This works pretty simple, the radio is supplied with a 3.5mm male-male stereo cable. Plug one end into the line-in port on the radio, and the other into your audio device. On the LCD screen, a “>>” symbol appears on the right-hand side. Turn the radio on, and get your source playing, you’ll hear it through the radio speakers.

Nice and simple. I’ll be able to use it with the aforementioned AR-1690, my tablet, and the little portable media player I already use on the bike.

MP3 Player

Yes, I did mention it has one. The controls are on the back, and the device takes a SD card via a port hiding under the rear stand.

The SD card port

Plugging in a FAT32-formatted SD card with some MP3s on it (The Goons Show, what else?) and turning the radio on, I then tried getting it to play something. Hitting Pause/Play at first seemed to do nothing, but eventually I must’ve either waited long enough, or managed to coax it to play something, it started playing the first track it found.

I could navigate between the tracks — I have no idea whether it sorts the files by file name or not, the display is too primitive to support showing any track metadata, but it did work. There’s no playlist capability in this device, no random shuffle mode, as I say, it’s primitive.

So I think I’ll just ignore it and pretend it’s not there. A Bluetooth receiver would have had greater utility, but never mind. There is a sister-model to this one, the PL398-BT with exactly this feature… but good luck getting one unless you order direct from China.

Hidden function #1: A lithium charger?

So, fiddling with the radio, I noticed a few hidden features that are undocumented. With the radio off, holding the VM button triggers the display to show “Li On” and the “Ni-MH Battery” indicator starts flashing.

Is this a “Lithium battery” mode?

Exactly what this is doing I’m not sure. There are radios in Tecsun’s line-up that do support and include Lithium batteries, so maybe the project to add this feature isn’t out of the question. I guess a trip into the set with a screw driver will be my next move, but maybe some of that work is done for me.

Hidden feature #2: Self test?

Holding the BW button whilst the radio is turned off seems to perform a self-test of the display.

All segments on the LCD turned on

When the button is released, it switches back to showing the time, plus some 4-digit code (firmware version perhaps?):

“3985”, a code for the gurus to meditate over

Not sure what this is.

Final comments

All in all, both seem to be decent sets. The little DAB+ set is more-or-less a one-trick pony, it’ll be interesting to see if it does any better or worse than the Tecsun. I’m also yet to introduce these to the Garmin GPS that caused my Sanyo so much grief.

It’s nice to know that short wave sets are still being manufactured, and the performance of this set is quite remarkable. Tecsun themselves are based out of Hong Kong, and seem to have a decent reputation from what I’ve seen in reviews online.

While lately it’s been my policy to avoid buying stuff that’s made in China / by Chinese companies — in this case the feature set I wanted was practically a unicorn, no one else makes something like this, and this set seems to perform decently, so we’ll see how it looks after a year or two to see how it is long-term. After all, the little Sanyo has been in my possession since the early 90s, and it was an old radio then… it still goes. Will the Tecsun last as long? We’ll see.

As for the Digitech unit; well, DAB+ has a crazy amount of DSP going on to pick out one station out of a multiplex. I expect being more complicated, it’ll perhaps have a shorter longevity, but hopefully long enough for me to cobble up a replacement. Time will tell.