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[IRCA] Tecsun PL-300WT DSP-enhanced Ultralight Radio-- Further Details
Hello All,
With a large number of medium-wave DXers apparently waiting to receive
their new PL-300WT's from the Chinese eBay sellers "Liypyn" and "Anon-co," more
information regarding this innovative pocket radio may be of interest.
The PL-300WT was thoroughly disassembled here to gain various technical
information, and the radio does indeed have some very unusual characteristics.
There is no alignment system designed for either the AM or FM bands, and
no frequency limit adjustments or upper-band trimming capacitors were found.
The new DSP chip was designed to provide optimum performance on both
bands, without alignment. Does it accomplish this purpose? Basically, yes-- the
out-of-the box performance was very good on my PL-300WT model, as reported
previously. However, despite the manufacturer claims, the loopstick can
indeed be aligned. Although its construction certainly doesn't make this job
easy, a hobbyist can peak the coil on a 600 kHz signal, and gain some
additional low-band AM sensitivity by doing so. The final aligned inductance of
the single coil is about 282 microhenries.
For the typical DXer who does not enjoy taking radios apart, the new
PL-300WT should be an ideal model, assuming that the same very good
out-of-the-box performance applies to other such radios. Tecsun's no-alignment design
is quite an innovation.
The PL-300WT's DSP chip apparently is designed to provide maximum
sensitivity on all AM frequencies when the loopstick inductance is fixed around the
282 microhenry value. This makes the PL-300WT's AM RF design significantly
different than that of the Eton E100 and other radios with single-coil
loopsticks, which benefit greatly from a Slider loopstick which can adjust
coil inductances along with the changing frequencies. In the PL-300WT, so such
adjustment is needed, and as long as the loopstick shows an inductance of
around 282 microhenries from the single coil, maximum sensitivity should be
possible. This means that although a Slider loopstick transplant will not
benefit the PL-300WT, a larger fixed-coil loopstick providing the 282
microhenry inductance will boost the sensitivity greatly (this has already been
done on the PL-300WT here, using a 7.5" Amidon ferrite bar wound with a
40/44 Litz wire coil). Photos of the disassembled PL-300WT have been uploaded
to the Ultralightdx Yahoo group site, for those interested.
The PL-300WT's front-panel access door to the world time selector switch
was stuck on my review model, and stubbornly refused to open. After
completely disassembling the radio, I gently attempted to open the access door from
the back side-- which made the door completely fall out. All attempts to
make it work have failed-- the time switch door has apparently decided it
was "time" to teach me a lesson. Beware of its flimsy construction.
As reported previously, the LW and SW bands on the PL-300WT are mediocre at
best, and my investigation confirmed that the LW band does not receive
signals from the loopstick. Since I've yet to receive any LW signals on my
review model, I'm still wondering how or if Tecsun really intended this band
to receive any signals.
In summary, the PL-300WT's out-of-the-box AM and FM performance is truly
remarkable, and more than justifies the modest $50 price, in my opinion. I
hope that the legion of DXers who have purchased this breakthrough DSP model
will be equally satisfied in the exciting medium-wave DX capability.
73, Gary DeBock
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