N9EWO Review :
PALSTAR LA30 Ferrite Loopstick Antenna
(prototype)


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).


What's 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) 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 current production
Quantum loops
, which use 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)

Balanced 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 ?).

The on-board 10-volt 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. 

Update : 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 ??

"NOTE : Powering the LA30 with more than 12VDC will cause the audio to distort. We supply a 9VDC wall adapter because at the current draw level of the LA30, its output is very close to 12VDC. The typical 12VDC wall adapter will have an output closer to 15VDC, which is too high for proper operation."

The Jameco 170245 regulated 12.0 volt  1 amp "wall wart" supply we use with the LA30 Prototype and works excellent (extremely clean, entirely non switching) . WARNING : A caveat as Jameco has started to use switching regulators in SOME of their older "linear marked" regulated adapters and with NO model number change that indicates this change (but does not affect all of them). We have experienced one of these changed new style adapters (was different voltage/model) with the switching regulator inside , and are unusable with any radio products (very RF dirty/noisy).

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 ones do.

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).


LA30 Prototype "Rear View"
(N9EWO photo)

Was This 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).

Our thanks again to Pete Gianakopoulos for the prototype test sample.

Dave N9EWO
c N9EWO, all rights reserved
ver. 2.2


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