[IRCA] Hot-Rodded Ultralight TP-chaser Shootout

[D1028Gary@xxxxxxx]

Hello All,
 
With nothing better to do on a relatively warm day off, I decided it was  
finally time for a competitive Shootout of the most sensitive and selective  
Ultralight radios ever used to chase TP's here, and at Grayland.
 
As most of the fanatics who enjoy this type of activity will recall, in the 
 early days of the ULR boom, experienced TP DXers quickly became bored 
waiting  for the rare propagation openings which would allow reception of Asian 
stations  on their SRF-59's, and other modest units. Since some of these 
DXers had just  enough technical knowledge to put their stock ULR's in serious  
jeopardy, a strange mission of transplanting monster loopsticks  and narrow 
filters commenced in early 2008, with mixed results. Nothing much was  
really accomplished until sensitivity and selectivity improvements were made in  
combination, such as in the Eton E100, with the 7.5" Slider loopstick, and  
Murata CFJ455K5 narrow IF filter (a concoction of John Bryant, Guy Atkins 
and  me).
 
Recently China's Tecsun company introduced their PL-300WT with the  
innovative DSP chip, from Silicon Labs. Although Tecsun's  manufacturing process 
unfortunately produced mixed results for AM sensitivity in  their new model, 
the DSP chip has certainly succeeded in providing a quantum  leap in 
selectivity for stock Ultralight radios. In testing against the  Murata CFJ455K5 
premium ceramic IF filter in modified E100 units, the  DSP-enhanced selectivity 
of the PL-300WT was found to be competitive or  superior on all frequencies.
 
Accordingly, immediate efforts were made to transplant a 7.5" loopstick  
into the PL-300WT, and test the radio against other heavily modified 
TP-chasing  Ultralights. Because of the design of the DSP chip's varactor component, 
a  single fixed inductance from the loopstick (anything from 180-450 uh,  
depending on the individual varactor) is used to optimize AM sensitivity on 
all  frequencies. This means that a fixed coil loopstick will provide maximum  
sensitivity throughout the AM band, once the correct inductance is found to 
 match the varactor. Assuming that the radio's final sensitivity would at  
least match that of the E100 and C.Crane SWP Slider loopstick models, such  
a system would provide a significant increase in DXing convenience, by  
avoiding the need to slide a coil to peak the radio's sensitivity.
 
Today, such a full competitive Shootout was finally conducted, in which the 
 new Tecsun PL-300WT with a 7.5" fixed-coil loopstick was compared with the 
Eton  E100 (with a 7.5" Slider loopstick and CFJ455K5 Murata filter) and 
the C.Crane  SWP (with the same 7.5" Slider loopstick and CFJ455K5 Murata 
filter). As  modified, the cost of the PL-300WT unit was about $85, while the 
other two units  cost about $150 each.
 
The Shootout was conducted in mediocre summer conditions, with the  fringe 
stations quite weak. Despite this, an accurate evaluation of the radios'  
relative performance was possible.
 
In relative sensitivity, the fixed-coil Tecsun PL-300WT slightly  
outperformed the C.Crane SWP Slider model, which in turn slightly outperformed  the 
Eton E100 Slider model. This was the judgement after all three radios were  
tested in the reception of four extremely weak fringe stations: KARI-550,  
KGMI-790, CFAX-1070 and Auburn TIS- 1700. A large part of the PL-300WT's  
advantage was its ability to tune in the stations on their fundamental  
frequencies without muffled audio, a side-effect of the Murata CFJ455K5 narrow  
filter in the E100 and SWP models. In the Murata filter-modified models,  tuning 
in the fringe stations 1 kHz away from the actual  frequencies improved the 
audio, but slightly decreased their signal  strength. This is unnecessary 
in the PL-300WT.
 
In the selectivity comparisons, three very tough fringe stations were  
tuned in adjacent to local pests: KPAM-860 in the shadow of KHHO-850, KFFX-1080  
in the shadow of KPTK-1090, and KUTI-1460 in the shadow of KSUH-1450. This 
type  of competition tested not only the sensitivity and selectivity of the 
modified  radios, but nulling ability as well. To improve audio quality in 
the Murata  filter-equipped radios, the stations were all tuned in 1 kHz 
farther away from  the local QRM than their fundamental frequencies (i.e. 861 
for KPAM-860, and  1079 for KFFX-1080). The DSP-enhanced PL-300WT once again 
proved to be  competitive with the other units, providing excellent rejection 
of the splatter  from the local pests. The adjacent-channel rejection 
provided by  the DSP chip was almost exactly equivalent to that provided by the 
Murata  CFJ455K5 premium IF filter in the modified E100 and SWP units, and 
all three  units were able to solidly receive the fringe stations without 
significant local  splatter. The balanced-frequency audio provided by the 
PL-300WT, however, would  have been preferable for the recording of MP3's in an 
actual DXing  situation.
 
In summary, the DSP-enhanced AM selectivity of the new Tecsun PL-300WT  
(and presumably the Grundig G8) is a major breakthrough for transoceanic  
Ultralight DX chasers, especially in combination with effective external  
antennas. It looks like an exciting fall DX season is coming!
 
73, Gary  DeBock                        
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