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



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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