[IRCA] PL-300WT Tests On Going - Part One

["John H. Bryant" <bjohnorcas@xxxxxxxxxxxxxx>]

I was/am really excited when the 300WT arrived on the scene. Beside 
the DXing possibilities offered by the DSP circuitry, the fact that 
it offers running numerical values of signal strength and S over 
Noise offered at least the possibility of running some semi-accurate 
antenna comparisons... The 300WT might be the instrument that I 
needed to do some development on multi-bar ferrite antennas, etc.
I ordered one and then an additional two PL-300WTs from the Hong Kong 
source and have just had time to spend about half a day with all three.
Some notes:

The three were all produced in May 2009 (sticker inside) and their 
unaligned stock performance was quite similar on weak signals. There 
were differences... one was always slightly better, one was always in 
the middle and one was always slightly poorer, but with these three, 
the performance differences were very slight.
Foolishly, I did not keep one stock and peak the antenna bar on the 
other two to see how much they improved.  Intuitively, the 
improvement was slight, if any.  As Gary and others have found, each 
of my units had the coil over at the left end.
Man. peaking these things is a whole new experience, after a lifetime 
of peaking up analog circuits without a varactor at work in the 
circuit simultaneously with the movement of the coil. These things 
have no real resonant peak.... rather, it is a plateau, or seems so 
to me. There is obviously a broad range of coil inductances that the 
varactor will compensate for, so the set is out of resonance at some 
point (for my three, that is with the coil partly off the bar) or it 
is in resonance.... as I slide the bar toward the center, there is no 
change in reception, despite me making major changes in inductance 
(by the sliding of the coil.)
There is less plastic in the PL-300WT than in the E-100.  The ferrite 
bar is only supported in a tray under the right-hand half of the 
bar.  The rest of the bar is suspended.... cantilevered out in space. 
This is probably why they are so enthusiastic in the use of glue in 
holding the bare bar onto the little tray under the right-hand 
half.  I was able to get two of the three antenna bars out, intact, 
after breaking the first one.  I did not find any "secret" to 
successful bar removal.... just patience and gentleness.
The varactor makes the antenna circuit so forgiving that I found that 
I could use my standard Plywood Slider boards and the coils that were 
designed to work with my E100s for the PL-300WTs.  I hold the radios 
to the boards with Velcro and have a set-screw arrangement in the 
Litz wires between the radio and the Sliding coil, so swapping radios 
and getting things up and running was very easy.
In the next day or two, I'm going to do another comparison of all 
three 300WT radios.... this time with all of them set up as 
Sliders.  I'll then pick the two most similar to use in antenna tests 
and return the third one to stock status for use in the Barefoot Class.
I did make one series of comparative tests last evening.... Between 
one of the PL-300WTs as an 8" Slider and my favorite TP DX ULR, an 
E100 8" Slider with the vaunted $50 Murata filter aboard. I checked 
the performance of the two on about 8 or ten weak signals throughout 
the domestic band, using my audio switching box that can switch my 
headphones back and forth instantaneously or put one radio in each 
ear.  The test was a real revelation.....  I'll be using the PL-300WT 
as my DOMESTIC DX receiver for the foreseeable future. The reception 
of these weak signals was at least slightly superior on the 300WT on 
each and every test frequency!!!  I'll not be doing much domestic DX 
out here in the Pacific NW, but I was beginning to hit difficult 
times in Oklahoma with 550 domestics, so a hot new receiver will be 
most welcome when I return to the Southern Prairie. The difference 
between the two radios was mostly in intelligibility... The very 
narrow Murata filter tends to muffle audio unless off-tuned one kHz. 
and you can't really do that on a very weak signal.  However, beside 
the boost in intelligibility, the 300WT did also seem a bit more 
sensitive, over-all.
I'm going to run a comparison between an E100 Slider without a Murata 
filter and a 300WT Slider to see if I can isolate/verify the gain in 
weak signal sensitivity a bit more.
Right now, I'm not convinced that the 300WT is the superior radio for 
all situations of TP DXing. It certainly has the HUGE advantage of 
not having to have a very difficult-to-perform IF filter transplant 
to be useful with off-channel TP or TA DXing.... and useful it will 
be.  However, there were instances last summer and fall where the 
Murata-filtered E100 just performed miracles of working in close to 
domestic channels. I'm thinking of 738 and 747 and even 1 kHz. splits 
where one could get useable DX signals "backing in" to the DX side of 
the pile.  Comparing the two sets here by just off-tuning a domestic 
by two or three kHz., I seem to hear slightly less domestic splatter 
with the Murata.  I'm not certain that is a totally relevant test. In 
truth, there is only one way to tell which can work in close the most 
successfully.... a trip to Grayland :>)
So far, I've not noticed any objectionable AGC action with my three 
PL-300WTs, and given the amount of weak signal work that I did 
yesterday, I think that I'd have noticed, were it a problem with 
these particular sets.
Back to work!  More later.


  
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