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[IRCA] PL-300WT Tests On Going - Part Two
Hi John,
Thanks for your detailed observations, which certainly agree with most of
the PL-300WT (and G8) experimentation here.
It was a big surprise for me to discover the "bulletproof" nature of the
new DSP radio, with its extreme resistance to overloading. I had been
testing a new 9-foot (side) PVC-framed passive loop in my backyard, which
previously had managed to overload any portable brought within 1 foot of its large
coil. The E100 (both Slider and stock) was especially bad, with multiple
birdies and false peaks all over the place. (With analog radios, the monster
loop simply "took over" all the tuning, forcing its resonant frequency into
the radio regardless of what frequency the radio dial showed).
The PL-300WT had no such problem, however. Both the stock and 7.5"
loopstick PL-300WT's were extremely well-behaved when inductively coupled to the
monster loop, receiving a great signal boost on the loop's resonant
frequency, but only when the radio's tuned frequency was the same as that of the
loop. The radio showed no false peaks, even when the loop was tuned to local
sloppers. This fact alone was amazing, and put the radio in a class by
itself among the portables I've tested.
In the shootout between a 7.5" Slider E100, 7.5" Slider SWP (both with
Murata CFJ455K5 filters) and a 7.5" fixed-coil loopstick PL-300WT, my results
basically agreed with yours, John. The DSP-produced selectivity of the
PL-300WT was easily a match for the Murata CFJ455K5 filters in the Slider units,
and had the added benefit of no muffled audio on the frequency of choice.
In the sensitivity comparisons, I found that the 7.5" loopstick PL-300WT
had a slight advantage over the fully-modified E100's and SWP's, primarily
because of the muffled audio from the Murata narrow filters on the frequency
of choice. Tuning these radios 1 kHz up or down improved intelligibility of
the audio, but slightly decreased signal strength, thereby giving the
PL-300WT a slight advantage (at least in my subjective opinion :>)
The Slider-only units (E100 and SWP) were competitive in sensitivity with
the 7.5" loopstick PL-300WT, however, with the Slider-only SWP showing a
slight edge over both the Slider-only E100 and the 7.5" loopstick PL-300WT on
all AM frequencies. Unfortunately, a Slider-only SWP is a non-starter for
TP DXing, with barn-door selectivity.
Like you, John, I will be taking quite of collection of stock and
hot-rodded Ultralights to Grayland, eager to see how they perform in actual
TP-DXing. The PL-300WT shows a lot of promise, but until it performs a few
"miracle receptions" like we have come to expect from the fully modified E100's, I
guess we will never be fully convinced, right? :>)
73, Gary
In a message dated 6/27/2009 8:24:45 P.M. Pacific Daylight Time,
bjohnorcas@xxxxxxxxxxxxxx writes:
Just kind of an interim Part Two for tonight.
I took the FM antennas off and the stock ferrite loops out of all
three units and put them to work as 8" Sliders. Set up that way, one
receiver seemed to produce just a bit better S/N ratio on the weakest
signals, so it was converted back to a Barefoot Class PL-300WT. I was
able to spend a couple of hours comparing one of the PL-300WTs and a
stock IF E100 with both set-up as 8" Sliders. I moved down our
mountain, at least 150 feet from any man made structure and (most
importantly) out of and away from my metal-clad house. The first
outdoor tests were very interesting.
The first thing that I discovered was that I had forgotten how nearly
useless an E100 Slider is here on Orcas Island. The
multi-powerhouses serving Vancouver and Victoria are all within 20
line-of-sight seawater miles of me here and an E100 Slider just
overloads like crazy. More than 50% of the dial is unusable from
splatter, birdies, images, slop and I don't know what all else....
its just awful. The PL-300WT was a real revelation,
though. Reception was possible on every 10 kHz. channel. Adjacent
channel rejection was just excellent. The only channels with any
slop/splatter at all were just a few frequencies where I was next to
the most powerful of the Vancouver stations.... There, I noted some
splatter, but the station assigned to that adjacent frequency was
very listenable/ ID-able to a DXer. The near bullet-proof nature of
the PL-300WT will be a real boon to urban DXers, allowing the use of
larger antennas, just as Gary has reported.
With all this wonderfulness surrounding the 300WT, I was surprised to
find that - in raw weak signal sensitivity - my E100s out-performed
the DSP circuitry of the PL-300WT on the lower half of the band.
There were only a handful of frequencies in the 700-900 range that
had weak signals that could be heard amongst the overload crud on the
E100... The most memorable was KXL-750, Portland (I was testing 6
hours before sundown.) This far North, KXL is really quite weak in
the day time. Time after time, the two E100 Sliders heard KXL better
than did the either of the two PL-300WTs. The same things was true
with a couple of stations in the 800s. However, above 1000 kHz., the
PL-300WT was the equal and usually the superior to either E100 (these
were all with stock filters.) I rush to say that all of the
differences were quite small... and usually involved S/N ratio.
It will be very interesting to see how these babies compare out on the
Coast.
I also noted the "AGC pumping" that Pete Taylor and a few others have
mentioned. I listened to a lot of weak signals today, and I only
heard the "pumping" three or four times. It seems to take the
perfect signal level to trigger it. At the weakest discernable
audio, things are very linear and normal. However on a signal that
is about language recognition level, there is a definite rather large
up/down movement in the volume with slight fades in strength. I
don't think that this is the AGC. If it were the AGC cutting in/out,
the volume would decrease from the existing setting as the AGC began
to control a signal. If my ears were working, in this instance, the
volume actually INCREASED abruptly and then dropped back down....
Like a pre-amp was cutting in for just a bit and then dropping back
out. In any case, its most likely in the gain algorithm (the
software definition of gain response) and something that we'll likely
learn to live with. Just slightly stronger signals or really weak
signals don't seem to exhibit this behavior.
I'm certainly in Ratzlaff's camp.... this radio seems to have a few
quirks, but it is such an outstanding performer overall that I'll
probably abandon my beloved E100s for domestic DX and almost
certainly for TP/TA work, too.
I'm learning more about the S/N and overall Signal strength readings,
too. They appear to be instantaneous readings.... a brief snapshot
taken every two or three seconds. There appears to be no averaging or
smoothing in these raw numbers.... I'd much rather see some small
amount of averaging to calm the readings a bit, but I do still think
that they will be a real help when comparing antenna systems. Also,
it appears to me that "25" is the best signal-to-noise reading that
the system can award... I haven't yet noted the maximum raw strength
reading. I suspect this numerical read-out is worthy of study and
discussion.
I'd love to know if my observations match or disagree with those of
others...
Tomorrow. I'm going to marry up the PL-300WTs to a 1" x 32" Ferrite
bar and to a 3/8" x 48" bar and try to do some comparisons...
What fun!!!
John Bryant
Orcas Island, WA
Winradio G313e and various Ultralights
Wellbrook Phased Array + Superloops
**************Make your summer sizzle with fast and easy recipes for the
grill. (http://food.aol.com/grilling?ncid=emlcntusfood00000006)
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