Medium Wave DXing with the REALISTIC DX-370

As I have mentioned previously, one of my hobbies is Long Distance MW radio listening. And one of the radios I use frequently is one that is hardly ever mentioned in MW distance listener circles, the Realistic DX-370.

The Realistic DX-370 -- like most Radio Shack portable radios -- was made by Sangean. In many cases Radio Shack just put their name on a Sangean radio and marketed it in their stores. In the case of the DX-370, they combined two versions of a Sangean model -- the ATS-800 and 800A -- to sort of make their own model.

When it first came out, the DX-370 was intended to be an 'entry level' model of digital readout SW radio. The larger DX-390 (a Radio Shack re-branded Sangean ATS-818) was more expensive and had more features, including SSB and a tuning knob. The 370 was more of a bare bones radio (less memories, no SSB, no tuning knob, less SW frequency range), but still was worth the money, as it worked rather well.


The DX-370 is a Sangean ATS-800A with Sangean ATS-800 firmware and features, but unlike either the Sangean 800 or 800A it tunes all the way up to 1710 khz on the MW band. The DX-370 was made in Taiwan.

The Realistic DX-370, a digital portable radio made in the 1990's. It was a budget Sangean digitally tuned AM-FM-SW radio. As you can see from this picture, the LCD display doesn't like 60F or less temperatures (106.1 Mhz is a local pop station in the Seattle area).

The DX-370 is a digitally tuned radio, but you just use the up and down buttons, which can tune very fast if needed. They speed up the longer you press down the up or down tuning button. This can take some getting used to for someone used to a tuning knob or direct-entry buttons. You have very little muting while tuning the radio.

Like the Sangean ATS-800, the DX-370 covers AM, FM, and SW in two "bands", on going from 90 meters to 41 meters, and the other SW "band" covering 31 meters up to 13 meters.

Like the Sangean ATS-800, and unlike the Sangean ATS-800A which the DX-370 is built upon, there is no 9 khz switch, which sucks if you want to take it overseas.

But the radio is actually capable of tuning in 9 khz steps -- one evening I turned my DX-370 on and it was tuning the AM band in 9 khz steps for some reason! It's the only time it's happened in the years I've had the radio. Obviously it was a microprocessor glitch, but it shows that there probably is a diode or resistor somewhere on the DX-370's PCB that keeps it locked in 10 khz mode. If it just had a switch added, it would probably tune in 10 khz or 9 khz steps -- the two khz standards for the MW band around the world.

The DX-370 has the best MW selectivity of all my portables except my Sangean PR-D5. It has the same ceramic filter used by the Radio Shack DX-398, as well as the same TA7758 IF chip.

It has narrow selectivity (sounds like maybe 5-6 khz bandwidth?) on the AM band, but it's not so narrow that the AM or SW bands sound muddy. The trebles are suppressed somewhat, but it has a full, listenable sound. And it has a pleasant sound through headphones, with more treble available than my PR-D5.

My DX-370 with the back off. I hard wired the FM/SW whip antenna to the terminal on the radio's PCB to keep it from ever breaking down or glitching. That's the white wire you see on the right side of the picture. I also added back-to-back protection diodes, which I ran between the whip antenna terminal and the negative side of the battery -- which also can be seen. The radio's 120mm loopstick can be seen, and also my power jack diode repair (diode soldered over the jack, extreme lower right of the radio's PCB) can be seen. I plugged in the wrong power supply by accident once -- it was the wrong polarity -- and fried the original power jack protection diode. I was lucky in that -- at that time -- I was unaware of how easy it is to wreck surface mount PCB connections. :-)

I use the DX-370 a lot because it is small, handy, tunes quickly, sounds good through headphones, it is probably the easiest Radio Shack or Sangean digital portable on AA batteries (especially for a digitally-tuned SW portable radio -- designed to work with 6 Volts, it can work on 3.6V according to specs). It has a clock -- which is handy -- if you want to check the time while listening you just toggle the middle button from radio to alarm to clock and back. It has an alarm which I think I've used once -- the alarm will switch on the radio or give you a piercing tone.

GOOD ON FM

The DX-370 is also is pretty sensitive on FM (it has a TA7358 FM RF amp chip). One Christmas when I took it with me to northern Louisiana I was able to hear FM stations from as far away as Longview and Nacogdoches, TX, as well as Texarkana, Arkansas. I would turn the whip and get two different FM stations from 100 miles or more away, in full stereo. It was amazing.

Another shot of the DX-370 with the back off showing the protection diodes (surrounded by thick, clear shipping tape) that I added to the radio because I'm not 100% certain it has them otherwise. The white wire hardwires the FM / SW antenna because of the way it's attached to the main PCB. I prefer my radios to have their whip antennas hardwired where possible. If you look carefully in the upper left hand side of the PCB you'll see "ATS-800A", which is the Sangean board the DX-370 is made from.

The DX-370 is one of my best FM radios, both in sensitivity and the rich, full sound you get through the headphones. It has FM in stereo through headphones, which is very nice. The memories are quick to program and very easy to use -- you get five memories on each band.

The back of the DX-370. AS you can tell, it's an updated model (the "A" in 20-211A designates an updated version of the radio). The back also says it tunes from 535-1705 on the MW band, which is a mis-print: the radio definitely doesn't tune in that range (unless the microprocessor glitches). It tunes MW from 530-1710, using the North American MW standard. It's an example of the DX-370 being unique to Radio Shack: it is an ATS-800A circuit board with ATS-800 features and North American X-band added on MW.

USING THE PROXIMITY EFFECT WITH A LONG WIRE ANTENNA ON SHORTWAVE

I also use my DX-370 to scan through the 49, 41, and 31 meter SW broadcast bands at night to see what's on. It tunes quickly up and down the band, and it's fairly sensitive off the whip. If you're in a low signal area, you can use it with a longer wire by clipping a wire to the DX-370's whip antenna, using an alligator clip. I often use a 25 ft. indoor wire (about 8-9 meters) with my DX-370, by alligator-clipping the antenna to the radio's whip.

If your wire antenna is longer than 25-30 feet (8-10 meters), you can place the radio's whip antenna near the wire antenna's feedline, using the "proximity effect" to boost signals to the radio. That way you can use a longer wire with the radio without overloading the DX-370's RF circuits. When I had a 100 ft. wire, I was able to hear much of the world this way without overload to the radio.

For example, one early evening a few years ago I heard Tunisia fade in and out on 41 meters. With just the whip, I could barely hear the station. When I placed the whip near the 100 ft. wire's feedline, it came in readable enough to catch an ID. The proximity effect is useful if you have a small radio with no external antenna jack. And one plus is you never have to worry about static charges frying an RF amp transistor.


The DX-370's LCD readout doesn't like the cold. If it gets down below 60F/10C it tends to fade on some of the characters.

It has a 120mm x 7 mm MW loopstick, which is probably very adequate if you are in a high signal area. If you're in a low signal area like I am, an external loop will make the radio shine on AMDX -- which it does.

I tend to use my DX-370 the most, of all my portables, for MW DXing, because of its convenience, quick tuning, smallish size, full sound through headphones, and good selectivity. As I live in a low signal area, I usually use an external loop with it when DXing. But I have read accounts by other radio aficionados who have used this radio in high signal areas without an external loop, and they have had good results.

GOOD MWDX RADIOS IF YOU CAN FIND ONE -- OF IF YOU ALREADY HAVE ONE

Although I haven't priced any of these radios recently, I think they are probably fairly inexpensive online, as they weren't "fancy", high end models with a lot of memories or extra features. A quick search shows some DX-370's for sale as low as $40 online, used.

For those of you who live overseas, where the DX-370 apparently wasn't sold, the Sangean ATS-800A undoubtedly has the same performance (as the DX-370 has an 800A board inside), and I would suggest you try it out on MW with a loop and see what you hear. I've seen some Sangean ATS-800A's for sale online at moderate prices.

A lot of DXers might even have one one of these radios around and haven't thought about using one to DX the MW band with. In my view it's well worth it to try it out on the MW band, especially if you have a loop. And when you're tired of MW DXing, switch it over to FM. The sound is really good (on headphones -- it has a fair sound through the speaker) -- and a DX-370 pulls in a lot of FM signals, too!

ADDENDUM, Dec. 1st, 2019:
I've noticed a couple comments to my article here, which is cool -- it means there are others using this useful little radio for MW DXing. Unfortunately, it seems to be difficult to respond to comments directly. In one of the comments, a reader asks if there is a service manual available for the DX-370. As far as I know, they are hard to find. I have been unable to find one in any of the online manual websites. Perhaps a service manual for the Sangean 800A would work -- I haven't looked for one of those, and I'm not sure how easy those manuals are to find. 

Information on these 1990's-era radios is unfortunately a bit rare.
73
C.C.