Art writes:
When I read Radio-Timetraveller's review of the Kaito KA321, detailing that radio's 3-notch tuning issue, I realized that I have the same tuning problem with a different radio. I thought my radio was a defective unit and have been using it as a paperweight.
A friend brought me back a nice looking radio from Europe, the Blaupunkt BTA-6000, a current model for Europe but made in China. It is a simple AM/FM/Aux Input unit approximately the same size as the Sony ICF-38. I had high hopes for this radio when I saw its sharp looks, only to be terribly disappointed by its quirky performance.
When tuning the radio, as I approach a local AM station it suddenly kicks in at about half volume; as I further turn the tuning knob, that station suddenly steps up to about double loudness; as I turn past the station the sound steps back down to half volume. I guess this 3-notch system is supposed to help me tune exactly to the middle of the frequency but I hate this frustrating feature.
Weak AM stations are much quieter in volume than locals. Also, when trying to listen to a weak station next to a local, the radio sometimes abruptly re-tunes itself to the local. It is nearly impossible to DX with this radio.
FM was satisfactory on this radio and it received weak college stations fairly well. I didn't test the Aux Input.
A quick look inside reveals the tuning knob to be a potentiometer not a capacitor, so this seems to be an analog-tuned digital chip radio. I could not read the writing on the chip.
The box of this radio says "Analogue" but I missed what should have been a tip off that the radio was not fully analog - the AM tuning dial is evenly spaced throughout the upper frequencies, which is uncommon for analog radios (except for the truly excellent Sony ICF-EX5mk2).
I love the earlier DSP chips in fully digital radios such as the Sangean ATS-909X and Tecsun PL-398. Those radios make listening enjoyable in urban areas (like mine) that have heavy electrical interference and too many locals. But this implementation of a DSP chip in a semi-analog radio is unsatisfactory to me. It's the worst of both worlds.
After this experience, I would not knowing buy an analog-tuned digital radio.
Finally, Radio-Timetraveller wondered how a European version of a radio with that type of chip would handle the 9kHz/10kHz difference. I am using a Europe-only semi-analog in the USA and have not noticed any additional problems due to the 9kHz/10kHz difference. It seems like the chip can adjust itself to work with equal performance on all continents and that is not a compliment.
What you have there is a varactor (a.k.a. varicap) tuned circuit. It is analog.
It's cheaper to use that kind of circuit than to use a tuning capacitor. It works, but unfortunately it can be rather unstable.
This was/is the problem with the GE/RCA Superadio 3.
Posted by: Drive-In-Freak | April 18, 2013 at 09:16 PM
A shame-that's a nice looking radio.
Sounds like a mechanically tuned DSP with the soft mute cutting in and out as you tune. I can't stand DSP radios for that reason
Posted by: dorpmuller | April 19, 2013 at 01:33 PM
If someone were to make a radio with that styling, with good performance, I'd buy it without hesitating. I love circular tuning dials.
Posted by: Keith Beesley | April 19, 2013 at 08:17 PM