This post is related to the ATS-20 I bought years ago, if you want to read posts related to the various ATS 25 - SI4735/32 I bought later, you can follow these links:
I write this in English because pieces of information related to this just born small receiver, are very scarce. Maybe SWLs "googling" will find this page more comfortable once written in English.
First I have to say that this receiver took me almost 1.5 months to get delivered from a chinese supplier, I bought it on amazon at around 50Euro. The time it took to be delivered was exactly as mentioned on the web page where I bought it, so I had no espectations to get this quicker. The small metal box comes with nothing: no re-charging cable, no instructions. Just put into a cardboard box.
The various models that one can find on the web may be branded or without any brand, mine one is branded ATS-20 and on the back is written: ATS-20 DSP receiver. Dispite the fact that it is described to cover a certain part of LW (153 khz - 279 khz), mine one covers from 149 kHz to 519 kHz and, connected to a good miniwhip antenna, it receives all the NDB I could test during late afternoon and aslo a couple of Navtex on 518kHz. Working in SSB I could also receive DDH47 on 147 khz tuning with the BFO which can go up and down in a range of -10,000/ + 10,000 Hz covering further +/- 10 kHz! (I stopped at 10,000 Hz..but it goes further up and down...I suspect to 99,990 Hz!!): I could receive the NDB SRN (330 kHz)in SSB at zero beat on 340 kHz with the BFO at + 10,000 kHz. Tuning 149 Khz and the BFO +9,000 Hz I could receiver the upper of the 3 EFR Teleswitching trasmitting station (nominally at 139,9 kHz).
But all above is just a curiosity.
In MW it covers 520-1720 kHz, in SW in various web pages it's written coverage between 2.3 MHz to 26.1 MHz, my model goes from 1720 Khz to 30,000 kHz, at least these are the readings on the (very small) display, I had not time to test it below 2.3 and above 26.1 MHz, probably it does not receive anything though the reading on the display is available.
UPDATE:
it receives DSC 0n 2187.5 and FT8 on 10m band (28074 kHz), so apparently it works also above 26,1 MHz and below 2.3 MHz.
BANDWIDTH FILTERS
Now the bandwidth filters. I have read on the web various values, my model has the following:
in SSB = 0,5 - 1 - 1.2 - 2.2 - 3 - 4 kHz;
in AM = 1 - 1.8 - 2 - 2.5 - 3 - 4 - 6 kHz.
DISPLAY
It's extremely small but readable, different models show the s-meter in different ways, mine one gives numbers: "S:1 -2 -3 - 4", other models give one or more lines depending on the signal strength. On the right of the s- meter there's a number 0 followed by a "%" which today were 2 "%%", after switching off and on again it showed a 100% which turned shortly again into a "0%%", I have absolutely no clue of what is that...I immagine it tells the charging status of the battery (??). Pushing the Bandwidth/AGC/Step selectors it turns to "%" and after selection is done again goes to "0%%". Tuning steps of main tunig and of BFO (which is again the main tunig knob after pushing) can be selected at 1 kHz, 5 kHz, 10 kHz in AM and 10, 25 Hz for the BFO steps in USB/LSB. AGC ON, Attenuation Mode, Frquency and Volume are shown as well "here and there" on the display. RDS in FM works pretty nicely, it takes some time to tune and show the broadcasted message, but definitely works.
BACK SIDE
Two switches are found there: on/off and FM/AM(SSB), the antenna BNC, the USB connection for recharging and finally the 3.5mm jack outlet for a headphone or any other audio connection to a laptop for decoding digital modes, recording, whatever..
IN OPERATION
With its telescopic whip, during the daytime I could get few shortwave stations inside the house, and many spurious signals from a couple of FM broadcasters. Connecting an external antenna, it magically turns into a good enough receiver. I made many comparisons between the SI 4732 and the Tecsun S8800 both connected to the same antenna through a small passive splitter (declared attenuation of 3.5 dB; frequency range of 0 - 1000 MHz; Made in China; Amazon supplied; priced 9 Euro; delivered in 24 hours). On both the radios I could receive same stations with comparable signal quality, of course the sound provided by the built in speaker of the SI4732, has nothing to share with the full and deep sound quality delivered by the Tecsun S8800 which remains - in my opinion - the best audio ever. The audio coming from the SI4732 internal speaker is anyway not that bad: of course connecting a good headphone or a good external speaker also the SI4732 gets to a fairly nice audio quality.
During the eveing on 7MHz band, with it's own whip antenna, I could tune various relay stations from Asia on air with programs from the most common broadcasters.
In SSB I made just a fast chek on Ham bands, decoding some WSPR in 10m band, listening short QSO on 20m, decoding some FT8 in 40m. Today morning and afternoon I kept it tuned on 12577kHz in DSC receiving with a Falcon OUT 250B: the receiver climbed fast the ranking of the spots sent to YaddNet, reaching rank 2 out of a list of more than 20 receivers connected and spotting.
When the battery gets close to be empty, the BFO start making crazy things: switching off and on gain at the same main tuning ad BFO readings, the signal is just not there anymore on the audio spectrum where it should be; re-tuning the BFO, you find the signal again but touching any other button it moves away. I thought this was linked to the almost empty battery, after recharging I could find the signal on the spectrum exactly where it should be with the proper tunig reading for BFO and main frequency. I have to say that on most of the bands the recharger can stay connected without creating noise, using an old mobile phone 5V recharger with a USB socket.
CONSTRUCTION
It seems to me a weak construction, the tunig knob has to make many turns to tune up and down the bands, I suspect that soon or late it will break; selectors for options (AGC, step, bands, volume, etc) are really very small even for child fingers; While the box is nice in itself, the front panel could have been designed with some more care to aesthetic.
What to espect more than this from a 50 Euro receiver with LW, MW, SW, FM RDS, SSB, DSP?
