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Re: [IRCA] ULTRALIGHT DXING
Gil, Russ and Barry,
Since yhe SRF-M37V, DT-200VX and SRF-T615 are being extensively
discussed, I couldn't resist sharing my own experiences.
The SRF-M37V not only has a selectivity issue in stock form, but also
has a spurious tendency in high-RF areas, making it undesirable in urban areas
with many locals. As Gil has noted, the SRF-T615 is indeed the top of the
line ultralight radio for sensitivity, although it also has moderate spurious
tendencies on the upper frequencies. The DT-200VX has the highest resistance
to urban RF issues among the digital ultralights, but it is not in the same
league as the SRF-T615 in the sensitivity capabilities. Selectivity of the
DT-200VX and SRF-T615 are similar, although my neighbor Guy Atkins has
engineered an excellent 450 kHz IF selectivity mod for the DT-200VX.
The challenge with the DT-200VX is getting it to have high sensitivity
on both the low and high end on the AM band. The design lacks the broadband
nature of the other two units, and alignment frequently makes it perform at a
equally mediocre level throughout the AM range. A user can typically choose
whether to favor the high or low end of the band by "hot-rodding" one side in
alignment, but typically this leaves the other side relatively deaf.
In two recent 6.25" antenna transplant experiments into the DT-200VX, I
finally had to decide to align one unit for the low band (520-1100 kHz) and
another for the high band (1100-1700 kHz), in order to cover the entire AM
frequency range with sensitivity comparable to an ICF-2010. For the average
user, the decision of purchasing the DT-200VX should be a question of whether
or not urban RF overload is a serious concern-- and if so, it (along with the
SRF-59 and SRF-39FP) would be an excellent choice.
73, Gary
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