N9EWO Review :
PALSTAR LA30 Ferrite Loopstick Antenna
The very pricey "Palstar LA30" Ferrite Loopstick Antenna on left.
Prototype built in a plastic case on right.
Both shown with the MW loopstick attached.
Laying on left side of the prototype's case is the "tropical band" element.
(left Palstar photo, right N9EWO photo)
Very Important Note : The review and information you read below was done with a PROTOTYPE of the Palstar LA30 Ferrite Loopstick Antenna, and may be different when compared to actual production samples. We have NOT tested a actual production unit at time of writing (and have no plans to do so).
Up With This Thing ? / High Quality Tuning Capacitor
OK, so I’m not a “Medium Wave DX” broadcast listener. I may tune casually around the band once in awhile and that’s about it. However in mid-August of 2008 I was very fortunate to obtain a prototype of a “Ferrite Loopstick Antenna” from the RF engineer Pete Gianakopoulos KE9OA (sadly is now a S.K.) who designed it for Palstar in Ohio USA. In the spring of 2009, the model number was decided as the "Palstar LA30".
IMPORTANT: What I cover here with this prototype may not be true with any “actual” production sample. For two, the prototype lacks the power and attenuator buttons. No internal AA battery holder either. The PC board (at least in the tested prototype) is of a high quality glass epoxy “shielded” type. The numbers on the 2 boards shown in the photo below are slightly different. The RF engineer gave me an "extra" PC board with no parts on it at the same time as shown in the picture below. I’m sure that other minor differences exist too ?
The large and geared tuning capacitor is used in actual production samples. The one installed in the tested prototype was smaller, however it's still larger than most caps that are used in gear today and even has ball bearings. But in either case it uses a much HIGHER quality capacitor over the now discontinued Quantum loops, which contain a tiny and much lower quality plastic transistor radio tuning cap (for example what you would find in a cheap $ 2. AM pocket radio ?).
The prototype was built in a large plastic box. Of course the production units are in a solid all metal case .
Production Palstar LA30 "7472401" PC Board w/parts (on left).
Prototype "7472400" PC Board with no parts attached (on right)
(left Palstar photo, right N9EWO photo)
Loop and FET Amplifier / How Well Does it Work ?
Very high Q and gain, approx. 20 db > area (for the prototype). Yes, very VERY SHARP tuning. Balanced loop / amplifier design using two surface mounted MMBF5486 FET’s followed by a MMBR941 output transistor. However, from viewing the "on line " owner’s manual and schematic, production samples use a MMBT5486 output transistor (or is it a MMBT5179 ?).
regulator is a nice touch however it was not used in the
prototype (bypassed) for the increased gain. I just have to
remember to use a 12 volt regulated wall wart with it (no
biggie). The web site and owner’s manual specifications list
the gain as 15 db.
: The text shown below in bold (and updated schematic) in a more
current version of the owners manual , points to the internal 10 volt
voltage regulator now being omitted. However this has not been
verified. But all the more reason to use a "non switching" 12.0 volt
regulated power supply with it (and NOT at 13.8 volts). I now have to
wonder IF Palstar ever used the 10 volt voltage regulator as in Pete's
original design from day one ??
From what I
can tell (with my limited MW loop experience) the
performance / gain is excellent using the MW loop with
equally excellent directivity as it's rotated. With the
PROTOTYPE “Tropical Band” loop, the gain is the same
but with less "sharp" tuning. This can be expected with
the frequencies involved. Rotating it does little to null out
noise/signal again with the higher frequencies. Also the tropical
loop was wound on a slightly shorter ferrite rod over the MW one
(remember : these are prototypes). Additionally I was told that
production samples are using slightly thicker ferrite rods. In
all cases the loops are wound using # 36 x 14 strand
“Litz” type wire. Additionally, these loops do not tilt
in any way and of course the Quantum
On ONE very strong 1 kW MW local signal, I had to kick in some attenuation (or slightly off peak the tuning) to control some minor "receiver" overload. But this was not a real issue and the production units have a switchable 15-db-attenuator button just in case.
This prototype coverage is from 520 to 1700 kHz on the MW loop element, and from 1700 to 5500 kHz on the Tropical Loop element (actually up to 6500 > kHz with reduced performance / gain).
Prototype A Winner ?? / Too Expensive
No…. it probably does not work as well as a larger loop, but considering the size of this antenna, this “prototype” of the LA30 performed very well indeed to my ears. It does not require all kinds of room either. If production units work any differently...…sorry I cannot say, untested as I type this text. Palstar does seem to have this loop overpriced in my view, and the LW and Tropical Loops are even sold separate adding to the already high cost (comes only with the MW loop).
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