[IRCA] Tecsun PL-380 AM Heterodynes (or lack thereof)

[D1028Gary@xxxxxxx]

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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