Re: [IRCA] [ultralightdx] DT-400W alignment

[D1028Gary@xxxxxxx]

To _Schuster@xxxxxxxxxx (mailto:Schuster@xxxxxxxxx) ,
 
     Thanks for your comments. I was the original  reviewer of the DT-400W in 
the 2008 Summertime Shootout, and have also  disassembled the radio 
completely, to compare it with the DT-200VX it  replaced.
 
     My three DT-400W review units all were ordered  from Amazon.com, and all 
three had equally good performance.  The wide-band  AM sensitivity was 
excellent across the band, and this performance has generally  been typical of the 
DT-400W reports from other DXers who have purchased the  model.  There have 
been at least two purchasers who were not fully  satisfied with their DT-400W 
performance, finding it not as sensitive as other  Ultralight models on either 
the high or low end of the AM band.  Most  likely, poor factory alignment is 
responsible for these substandard DT-400W's,  and a request to Sangean for a new 
AM alignment might be an option, if the  radio is still within the warranty 
period.
 
     The DT-400W's RF circuit board has been  extensively redesigned from 
that of the DT-200VX, making it next to impossible  for a hobbyist to align the 
1400 kHz trimmer while the radio is  operating.  No doubt Sangean maintenance 
technicians have the two  multi-pin jumpers necessary accomplish this, but a 
hobbyist would  need to construct these jumpers out of cannibalized parts using 
significant  time and expense, which is impractical unless the hobbyist would 
do these  DT-400W alignments routinely.  In the summer, I gave serious 
consideration  to making these two multi-pin jumpers, but since the user reports have 
 generally been excellent for the DT-400W, there really hasn't been enough  
demand for alignments to make such a project worthwhile.
 
     Poor sensitivity on the lower part of the  DT-400W's AM band can be 
usually be easily corrected by peaking the loopstick's  coil on a 600 kHz  (or 
thereabouts) weak signal, however.  For those  unfamiliar with the construction 
of Sangean's DT series, the loopsticks are  typically buried at the bottom of 
the radio cabinet, meaning that inverting the  radio can sometimes provide a 
slight boost in AM sensitivity, and nulling  ability.  The loopstick itself is 
well designed, and technicians have  discovered a major boost in sensitivity 
simply by relocating the stock  loopstick outside the cabinet.  Sangean buried 
the loopstick at the bottom  of the cabinet in the DT-400W (and DT-200VX) to 
avoid digital RF hash at the top  of the cabinet.
 
     73,  Gary  DeBock           
 
 
In a message dated 1/17/2009 4:40:23 P.M. Pacific Standard Time,  
schuster@xxxxxxxxx writes:

 
 
 
Just got a Sangean 400W from Buy.com and am comparing it head to  head
with my original, old DT-200V.

Sensitivity seems comparable;  frankly I at first blush I can't detect
the described difference wherein  the 200 is more sensitive at one end
of the band than the other, compared  to the 400 which is more uniform
across. Frankly, also, the selectivity on  the 200 seems a bit tighter
and it nulls slightly better.

Further,  the audio of the 400W seems "hissy". On further tuning
around, I'm  convinced this may be as much a function of the audio
circuit and speaker  design, as the alignment. It seems the 400W's
alignment is a KHz or so off  center (or the filter is not quite
symmetric) as I listen 10 KHz above and  below local powerhouse stations.

Did I get a poorly QC'ed 400W? Would  you bother trying to exchange it?
How about return to Sangean? Those who  have opened the case - is there
a readily accessible tweak that would allow  me to return it better to
spec?  (mailto:ultralightdx-unsubscribe@xxxxxxxxxxxxxxx?subject=) 

.

 
__,_._,___ 

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