Thursday, May 18, 2023

A Review Of The XHData D-109 DSP Radio

Next up, let's talk about the new XHData D-109 DSP radio. I ordered one from Amazon last week and it came over the weekend. It was just over $30 with free shipping from XHData using Amazon Prime.

The D-109 is a beautiful little radio, slightly larger in height and width than XHData's analog DSP radio, the D-219. It measures out at 6 inches wide, 3-1/4 inches high, and 1-1/4 inches thick. It is quite a bit larger than the RadiWow R-108.

XHData D-109

Full coverage of mediumwave is available - 520 to 1710 kHz. All AM bandwidths are available - 1,2,3,4,6 kHz. It tunes in 1 kHz steps. The radio also covers the longwave band. It came pre-activated on my radio, but may be disabled if you wish. Shortwave coverage is complete, from 1711 kHz to 29999 kHz. FM coverage ranges from 64 to 108 mHz, seemingly all in one band.

Fit and finish is good. The sound from the front-facing speaker is very pleasant, as others have stated. Two watts of audio are available. It has impressive battery life with the lithium 18650, 2000 mAh battery. I've been running it using the speaker for several hours per day for nearly a week, and the battery still shows a full charge. Charging is through a typical USB cable plugged to a 5 volt source. The XHData designers have used a USB-C style connector, a bonus.

I found the tuning knob is a little small, but adequate. Frequency entry on the keypad is direct and immediate, like the Tecsuns have, nice. No extra buttons to press. Keys are robust and click with a tactile snap, and feel like they'd last a long time. The display is backlit with a nice soft golden yellow color. The display is crisp and clear, but otherwise typical for a digital DSP radio. It shows battery charge, clock time, alarm times, temperature, and receive RSSI (in the typical dBµV) and SNR (signal-to-noise) levels.

The radio has a clock, two alarms, and a sleep function. A scan function scans any band of interest quite nicely. Plenty of memories are available for those who use them. 100 each for FM, longwave, and mediumwave, 300 for shortwave.

The radio supports bluetooth and can be used to play audio from an external device through its bluetooth connection. It also sports a TF card slot for a micro SD card, which can be loaded with music and played through the radio's audio system. Allowed formats are: MP3, WMA, WAV, and FLAC. Recording of received station's audio is not possible, unfortunately. At least as far as I can tell.

For mediumwave, the 10/9 kHz channel step choice is easily set by holding down the 2 key for a couple of seconds when the radio is off. Tuning is interesting. The radio seems to be locked at a 1 kHz tuning rate (10 kHz for FM) unless you rotate the tuning dial quickly, which then goes into fast tune and steps at 10 (or 9) kHz (mediumwave) or 5 kHz (shortwave) or 100 kHz (FM). For example, on mediumwave, tuning slowly tunes as such...  the frequency changes: 620..621..622..623..624..625..jump to 630. They've elected to advance to the next channel when you pass the 5 kHz halfway point. There are channel up/down buttons too. The channel up/down buttons only step up or down 1 kHz at a time, and no convenient channel jump at the 5 kHz halfway point. I feel it would have been better for channel up/down to advance at the user's chosen 9 or 10 kHz step and not 1 kHz. Maybe someone has figured out something which circumvents this.

Mediumwave sensitivity is exceptional. I did some signal strength comparisons with the R-108 and it is identical, or better. Even the RSSI (dBµV) readings are within one or two dB. It is more sensitive than my larger old school analog Tecsun R-9700DX, slightly better than my D-219 DSP analog, way better than my Sangean SR-35 and Dreamsky DSP analogs. In fact, it holds its own against my PL-880 and Sangean ATS-909X. That's impressive. Now comes the problem.

Shortwave is the problem. Maybe not a fair test here, as I am within 1.5 miles of two 5000 watt stations. I am bathed in more than 200 mV/m from each of those stations, 266 mV/m from one. Those are truly clobbering signals, 1/4 of a volt per meter. My SDRs can barely handle it. Intermod and overload on shortwave coming from the mediumwave band, particularly between 2-8 mHz, basically makes shortwave unusable for me at this location. An initial trial in the country about 4.5 miles from a 20 KW transmitter had a similar negative result. I need to take this radio well out into the country, far from mediumwave transmitters, and see if that makes a difference.

I was convinced I could remedy this but could not. I plugged in an external antenna, running the coax feed through a 30 dB (attenuation) RTL-SDR broadcast AM Reject filter in series with an old Grove TUN-4 preselector for the shortwave bands. It did not work, in fact it was worse. Experimenting with a shorted piece of coax with no antenna connected, I discovered that part of the problem is that mediumwave signals are somehow being funneled into the radio via the antenna ground (the coax shield). The longer the shorted piece of coax got, the worse was the intermod. More experimenting is yet to come. Shortwave above 41 meters is a little better, but still hit and miss, though when I was able to null the mediumwave interference a bit, shortwave sensitivity seemed good.

The whip antenna on the D-109 is 21 inches in length like its analog cousin, the D-219. Warning, don't do this! I removed the whip antenna by unscrewing the bottom mounting screw, and pulled the whip from the radio. Unfortunately XHData in their design wisdom have decided to solder a connecting wire directly to the bottom of this screw, and the wire broke off. There is no fixing this unless you pull the case apart, a nasty job on this radio, affirmed by Gary DeBock in his teardown of the D-109.

The radio works wonderfully on MW with an 18 inch tuned box loop. The sensitivity, already very good, is outstanding when coupled to the loop.

Bottom line so far: Great radio for mediumwave. I'm not an FM fan, so no FM testing was done. If you want something for shortwave, you had better be sure you live in a rural area away from high power AM stations. $30 seems a good price point for this radio. It's a keeper for me, and has become my morning driver radio.

No comments: