[IRCA] Supercharging the Tecsun PL-380- A 7.5" Loopstick Transplant

[d1028gary@xxxxxxx]

Hello All,
 
The new Tecsun PL-380 DSP radio is the latest refinement in high  
performance pocket radios from China, offering very effective 1 kHz DSP  selectivity 
for AM-DXers, as well as freedom from the "soft mute" issue  troubling 
previous DSP models. With superior FM and SW capabilities, this new  Ultralight 
model has a lot to offer for its $46 (plus shipping) price.
 
The full PL-380 review was being completed here to detail this model's  
impressive capabilities, but there was a slight detour due to an unexpected  
delay. In checking the PL-380's stock loopstick, it was discovered that the  
ferrite bar was small and poorly designed, and that the loopstick coil had a  
serious inductance mismatch with the 4734 DSP chip, resulting in  
less-than-optimum AM sensitivity. For a dedicated TP-chaser demanding extreme AM  
sensitivity to match this models's outstanding AM selectivity, this was simply  
an unacceptable situation-- so everything was dropped to design an 
effective  7.5" loopstick transplant, and install it in the PL-380.
 
An 81-turn Slider coil was used to find the optimum AM inductance match  
with the PL-380's 4734 DSP chip, then a new 81-turn fixed coil of 40/44  Litz 
wire was wound on a 7.5" Amidon Type 61 ferrite bar, with inductance  
matching the 554 uh value for optimal AM sensitivity. The new loopstick was  
soldered into the PL-380's circuitry, providing an average 20 dBu boost in  
signal strength on all AM frequencies (as well as a massive increase in LW  
sensitivity). It was then mounted on a custom plastic frame attached  to the 
PL-380's top front cabinet section, and was tested on both AM and LW for  
weak-signal performance. The modified radio has been found slightly superior in  
transoceanic DXing performance to any of the previously modified ULR radios,  
including the E100 Slider models. Both the AM and LW bands received a 
tremendous  sensitivity boost because of the loopstick transplant, opening up a 
new world of  weak-signal performance on both bands.
 
The Microsoft Word article describing this 7.5" loopstick transplant  
procedure has just been completed, and is suitable as a guide for experienced  
hobbyists to complete this PL-380 transformation. It is available currently  
at  
_http://www.dxer.ca/file-area/cat_view/87-ultra-light-radio-files-area/95-ulr-radio-modifications_ 
(http://www.dxer.ca/file-area/cat_view/87-ultra-light-radio-files-area/95-ulr-radio-modifications)  on  DXer.Ca (the first 
option on the list), in the Yahoo Ultralightdx file  section (Alignment and 
Modifications section, last option on the list), and also  directly at the 
following link:  
 
 _http://www.mediafire.com/?vnjhmkmazxx_ 
(http://www.mediafire.com/?vnjhmkmazxx)  
 
The delay in completing the full PL-380 review is regretted, but hopefully  
this new loopstick design will be of interest to those DXers demanding 
maximum  AM sensitivity to match the PL-380's razor-sharp selectivity. With this 
 effective combination, the new PL-380 can certainly fulfill its potential 
as a  legendary 9 kHz-split DX chaser.
 
73, Gary DeBock (in Puyallup, WA)
 
 
 
 
 
 
 
     
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