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Tuesday, March 26, 2013

Si483x-based Kaito KA321 DSP Receiver Ordered

It's looking more and more like the proposed Tecsun R-2010 may never see the light of day. No matter, I've ordered a Kaito KA321 from Amazon yesterday which uses the same Silicon Labs receiver chip, the Si483x. The '321 seems to be the DSP second-cousin of the Kaito WRX911 and Tecsun R-911 and the analog DSP sister of the Tecsun PL-380. Tecsun also produces a radio using this chip in the DE-321.

The Si483x is another of Silicon Labs' chips developed for consumer AM/SW and FM operation. This second generation mechanically-tuned digital CMOS AM/FM/SW radio receiver IC integrates the complete receiver function from antenna input to audio output into one chip, like the Tecsun PL-380's Si4734 digital chip did. The difference: this chip is analog-tuned.

Maximum band coverage of this chip is 504 KHz to 1750 KHz in the mediumwave band, 5.6 MHz to 22.0 MHz in the shortwave band, and 64 MHz to 109 MHz in the FM band. The 120, 90, and 60 meter tropical bands are not available. Neither is the longwave band.

AM sensitivity is comparable to the Si4734 chip, at 30µV input for 26dB (S+N)/N (signal plus noise to noise). The PL-380's Si4734 chip had a typical 25µV (S+N)/N sensitivity.

As an added bonus, use of a mechanical resistive tuning pot allows the frequency to be displayed in a linear format on the dial, so frequencies at the high end of the band are not crammed together as with capacitive tuning. It should make tuning a lot easier.

The Radio Shack 12-586 AM/FM Pocket Radio also uses this same chip and has had some positive reviews in the press. Reports are that AM sensitivity is good.

The '321 has been out of the gate for awhile, since about Fall 2011. I'll try to do a mini review soon. This being an analog-tuned chip, it will be interesting to compare real-world sensitivity and tuning differences between this and the Tecsun PL-380's digitally-tuned chip.

Kaito KA321 AM/FM/SW DSP Receiver

12 comments:

gkinsman said...

Bill,

Hopefully the DSP makes for excellent FM reception. I've got the similar looking, purely analog Tecsun R-9012, and the FM on it is absolutely hideous (the same station appears at multiple spots on the dial, many stations cannot be received at all).

-Gary

RADIO-TIMETRAVELLER said...

Hi Gary,

Will definitely check it out for you. I want to compare it closely to the Tecsun PL-380 and see how the analog differs.

Bill

Raj said...

My Tecsun 380 goes silent with antenna input of more than 50mV. Such big signals may not show up in real life but I am wondering why!

RADIO-TIMETRAVELLER said...

Raj,

It would depend on what frame of reference you are using. The PL-380 measures antenna input in dBuV, or dB above 1 microvolt. 50 actual millivolts (mV) would blanket the receiver if across the antenna terminals. 50 millivolts per meter field strength might not. Local station WYSL-1040 in Avon presents about 175 mV/m field strength at my location, but the PL-380 handles it quite well.

Bill

gkinsman said...

Bill,

One big disadvantage of an analog DSP radio is that you lose the ETM mode of the digital DSP radios (like the PL-380). This works so well that I sometimes use my PL-380 as a spotter receiver for my Satellit 800 or CCRadio-SW on shortwave.

-Gary

Dr. Coyote said...

I've had one since October, and it's great. FM is very good, and SW & MW are just a notch less good than my Tecsun 380. Head and shoulders over the 911, and for about the same price.

The analog tuning is a big plus here, because it's simple. Gave away a handful of them to family & friends at Christmas because it is so easy to work.

Looking forward to your review. I'm guessing you'll like it.

Raj said...

Bill, the signal level was at the antenna. It was fed from a HP test set. Tecsun 600 and 660 and many others I own show no distress at this input. The 380 goes completely silent!

Bugmethx said...

Any updates on the review? Thanks!

RADIO-TIMETRAVELLER said...

Thanks for your comments guys.

I have the radio in hand and will try to get working on a review this week.

Raj - I guess the unprotected front end of these one chip DSP sets is a little more vulnerable than I thought!

Bill

Stephen said...

Hi Bill,

I picked up a 12-586 at Rat Shack last week to try it out. I also bagged a 12-587, a similarly-sized digital display radio.

Here's a mid-afternoon bandscan on the 12-586.

I notice (as you may als see) that it likes to "lock" onto stations when possible. When tuning, I notice it doesn't start with the garbled splatter then as you approach center it smoothly cleans up, it starts as nothing then jumps into in-tune reception. Going from one station to the next is also jumpy.

A huge deal breaKer for me is that even though it has the very good selectivity to be expected from an SiLabs chip, tuning across it completely misses a lot of weaker stations. One way to tune these in, at least higher on the band, is to use another radio's local oscillator to generate a stronger carrier to lock onto. BUT, when turning the 12-586 off then back on, it often "snapped" to a nearby strong station. (I recorded a video but it didn't come out right.) A few examples are below. The desired station is first, then the pest. Approximate dBu readings are from the PL-398mp.

1620 WNSB415 (~21 dBu) vs 1630 XEUT (~51 dBu)
1490 KSPE (~teens-low20s) vs 1470 XERCN (~58-60)
~1370? - was getting 1360 KLSD (~66-68) off-tune splatter, interestingly tuning the other radio caused the RS to lock onto 1360.
1280 KFRN (~26-28) vs 1270 XEAZ (~52-54)
1190 KGBN (~16-20) vs 1170 KCBQ (~80, ~125mV/m)
1110 KDIS (~22-24) vs 1130 KSDO (~75-76), 1130 splatter or 1090 XEPRS (~52-55) on various attempts.

This behavior is quite annoying to me, so the radio is very likely going back unless I can find a GOOD reason to keep it.

Also here's a 12-587 bandscan. For several seconds when tuning a frequency, often there's a lot of noise. Some frequencies also have a carrier which interferes with a station, a prominent example being 570, occupied by KLAC.

For comparison, here's a Sony SRF-M37W bandscan recorded around the same time. (This radio's AM filter was replaced with a somewhat tighter one.)

RADIO-TIMETRAVELLER said...

Hi Stephen,

Thanks for your detailed report. I have much the same feeling about the KA321. Will have more to say in the review.

Thanks also for the info on the 12-587. Was wondering about this radio. By the way, the 12-587 video showed "private" so could not view it.

Bill

Stephen said...

Thanks, Bill. Apparently a few recent videos were uploaded with the wrong visibility settings, but I fixed them.

73, Stephen