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[IRCA] Tecsun PL-380 AM Heterodynes (or lack thereof)
Hello All,
There have been several questions regarding the new Tecsun PL-380's
susceptibility to internally-generated AM-band heterodynes, a quirk
affecting of all the S/L 4734 DSP chip radios (PL-300WT/G8, D92L, D96L and PL-310)
manufactured so far.
Although a full review of the Tecsun PL-380 is being drafted, for
those considering a quick purchase, a comparison was made of the internally
generated heterodynes showing up on the PL-310, and on the new PL-380.
Although there is only one PL-380 review model here currently, at
least on this single model, the AM heterodyne issue seems to have been reduced
from the PL-310's problem level. Tecsun has obviously changed some of the
circuitry in the PL-380 so that in general the heterodynes are less
obtrusive, although they still do exist on the AM band. The heterodynes in both
models can be reduced or eliminated by switching the DSP filtering down to 1
or 2 kHz, although whether this solution will be acceptable probably
depends on the type of DXing done by the user (for 9 kHz-split DXers, it would
probably work fine).
During daytime testing here, both the PL-310 and PL-380 have a
moderate 2 kHz heterodyne on 621 kHz (with 620-KPOJ at a medium level). On 1404
khz the PL-310 has a moderate 1 kHz heterodyne, while the PL-380 has none.
Both units have a weak 1kHz heterodyne on 1430 kHz (with a medium level
Bremerton station on the frequency). The PL-310 has also has a 1 kHz heterodyne
on 1431, while the PL-380 has none. (NOTE: Because of its soft-mute-free
operation, the PL-380 will typically receive a 1430 kHz domestic station at
a good level on both 1429 and 1431 kHz, whereas on the PL-310 the soft mute
function will cause a severe drop off in 1430 kHz signal strength on these
frequencies, leaving mostly the internally-generated heterodynes).
On 1602 kHz the PL-310 has a strong 1 kHz heterodyne (with a moderate
KVRI-KOHI mix on 1600 kHz), while the PL-380 has none. On 1640 kHz, however, I
did find a moderate 2 kHz heterodyne on the PL-380 that was absent on the
PL-310 (the only frequency on the AM band that I could detect such a
situation).
Since there is only one PL-380 review model here, the sample base is
limited, and other PL-380 users (Roy in Australia, and Rob in London, Ontario)
may wish to add their comments. There already seems to be an AM sensitivity
difference between my PL-380 and Roy's model, based on comparisons with the
PL-310's we both have (my own PL-380 seems equally sensitive on AM with my
two PL-310s, but Roy's does not). Since our current sample base is limited,
two more PL-380's have been ordered from eBay's "Anon-co," to give us a
clearer picture of the AM sensitivity situation on this model.
In general, the PL-380 here has performed like a dream in TP-DXing, and may
well be the ultimate $45 bargain in AM-DXing history.
73 and Best Wishes,
Gary DeBock (in Puyallup, WA, USA)
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