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[IRCA] July 12 Grayland DXpedition and 8' Tuned Passive Loop Performance
Hello All,
When John Bryant mentioned to me that he was planning a mid-July trip to
Grayland to chase DU's (South Pacific DX from Australia, new Zealand and the
nearby islands), I eagerly booked a room at the Grayland Motel to chat
with him about various Ultralight radio experimentation, and to test out
various hot-rodded pocket radios is the very tough mission of DU-DXing. Recently
the Ultralight radio community has been thrilled with the introduction of
the Tecsun PL-300WT and Grundig G8 DSP-enhanced pocket radios, and this was
an excellent chance to test their AM selectivity against the premium
Murata CFJ455K5 filters installed in the modified Eton E100 and C.Crane SWP
Slider models (developed last year, in cooperation with Steve Ratzlaff, Guy
Atkins and John Bryant).
Besides this, during the spring I had experimented with different frame
designs for tuned passive loops, and had discovered a way to make practical,
lightweight PVC-framed loops much larger than the traditional 4'
wooden-frame designs. Inexpensive, practical PVC-framed tuned passive loops of up to
9 feet per side were developed at my home in Puyallup, WA, providing
extremely high DXing gain when inductively coupled to any type of portable radio.
Wistfully thinking about how effective such monster PVC-frame antennas
would be at Grayland, I quickly modified the design to develop a collapsible
frame 8' (diagonal) version that would fit in my compact car for ocean
beach runs, and which could be easily assembled in total darkness within a half
minute. An all-PVC altazimuth tilting base was also developed to optimize
nulls on these monster loops, which was also small enough to fit in my
compact car (along with both the 8' and 6' collapsible-frame PVC loops). This
would be my first chance to test out these fanatical creations!
John and I had a great 4-hour chat on Saturday night about our mutual
experimentation, DXing in Oklahoma and other matters. But with the notoriously
early dawn enhancement for DU-DXing, we had to cut it short to prepare for
DXing at around 1030 UTC (0330 local time). John and I would both test out
the new DSP Ultralights against the Slider E100's developed last year,
while I would also try out the Slider C.Crane SWP units, developed with Steve
Ratzlaff last winter. John's objective was primarily to chase new Ultralight
DU loggings with his Wellbrook Array, while my goal was to evaluate both
the new DSP Ultralights and the new 8' collapsible-frame PVC loop.
Because an 8' Loop is a little too large to set up indoors (except perhaps
in an auditorium), my DXing station was set up in total darkness at a
picnic table location on Grayland Beach Road around 1400 UTC. Light drizzle
made the process interesting, but the 8' Loop itself had already been
completely waterproofed, and the main challenge was in juggling a vast collection of
receivers, recorders and logs to evaluate everything within a short 2-hour
dawn enhancement period. I was using a slightly modified Sony ICF-2010
(with a 30" transplanted loopstick) as my SSB spotting receiver, and it again
proved extremely valuable in evaluating propagation shifts, DU station
carrier strengths, etc. I thought that this modified ICF-2010 was great for AM
sensitivity-- but that was before I tried inductively coupling it to the 8'
passive loop!
John and I both noticed a great signal from Tahiti-738 at the beginning of
the dawn enhancement around 1130, with a strong domestic (KCBS-740) only 2
kHz away. This gave us a chance to test out the DSP-provided selectivity in
the PL-300WT against the Murata filter selectivity in the Slider E100's.
We both immediately came to the same conclusion-- the Murata filter had a
clear advantage in limiting the domestic splatter, and providing a superior
S/N ratio.
The ICF-2010 spotting receiver checked various "big gun" DU frequencies
(567, 612, 639, 657, 702, 738, 774, 792, 891, and 1116) for possible audio,
and found weak audio on most of them after 1200 UTC. Bringing the modified
ICF-2010 into the inductive influence of the 8' passive loop was a real
surprise, however-- once the loop was tuned to match the frequency, it typically
boosted the modified ICF-2010's received signal by about 3 LED lights,
making weak-sounding DU audio much stronger. Grabbing the C.Crane SWP Slider
Ultralight radio and repeating the process, I was amazed that some stations
like 4BC-1116 and 4RN-792 boomed in like locals, and provided very strong
audio for MP3's.
It took a while to develop a routine for chasing the weaker DU's with this
all-new setup, but once the modified ICF-2010, C.Crane SWP Slider and 8'
passive loop were used as a team to maximum advantage, the results were
thrilling. The exciting thing was that the 8' passive loop seemed to provide
its turbo-level boost to any portable brought within 3' of its massive coil,
whether it was a 30" loopstick ICF-2010, a 7.5' loopstick C.Crane SWP
Slider, or stock analog Tecsun R9012. Although I wasn't really trying for new
Ultralight DU's, I did manage to receive quite a few loggings on Sunday
morning:
531 UnID Weak music around 1227, but no ID's
567 2YA The strongest NZ station of the morning, had talk program at
1247
612 4QR In and out with talk around 1237
639 R.Fiji Weak choral music at maximum dawn enhancement
648 UnID Moderate audio around 1213, presumed R. Rhema
657 2YC Music at 1156, almost as strong as 2YA-567
670 KPUA (Hilo, Hawaii) booming in with ID at 1259 for strong MP3
738 R.Tahiti Strong in French at 1226 over 2NR co-channel Aussie
774 3LO Strong with talk at 1232
792 4RN Instrumental music booming in at 1240
891 5AN Moderate signal with talk program, still there at 1305
1116 4BC Extremely strong signal with "Sharina the Psychic" program at
1214
After collapsing the 8' loop and returning to the Grayland Motel, I was
more than a little surprised when John pronounced the morning as "low
average." From the biased perspective of the gain provided by the 8' loop, I
thought it was my best DU morning out of the 5 Grayland trips so far.
Local-sounding MP3's from 4BC-1116, 4RN-792 and KPUA-670 are available upon request
(as well as a photo of the 8' collapsible-frame PVC Loop).
So what is the verdict on the 8' tuned passive loop, as compared with
other DXpedition antennas? To be sure, there are certain advantages and
disadvantages with every antenna, depending upon the location and situation. Every
antenna has tradeoffs, but in the case of the monster passive loop, the
comparison with a beverage antenna is particularly interesting.
Both systems can provide great DXing gain, but a beverage antenna can
optimize DXing in one direction of choice. It also can be easily transported to
a DXing location, but requires a great deal of real estate for effective
operation. It requires no construction, and can be easily connected to an
indoor location.
A very large tuned passive loop has a "figure 8" reception pattern in
general, but can effectively null out pest stations (especially in combination
with an altazimuth base). It also provides an additional tuned circuit to
aid in selectivity, and rejection of nuisance signals. It comparison to the
beverage, it requires very little space for normal operation, but more
space for transportation. It can be erected at a picnic table location at a
public park, and smaller versions can be set up in motel rooms. Tuned passive
loop antennas are generally less susceptible to electrical noise, and can
be optimized for LW frequencies. But they must be physically near the
receiver for best operation.
In summary, a comprehensive article describing the PVC Loop experimentation
will be completed shortly, with variant articles describing the
Collapsible Frame variant, the Longwave variant, the 18" and 2' Tabletop variants,
and 6', 7', 8' and 9' Fixed-Frame MW variants, and the Waterproof variant
articles published shortly after. It is hoped that this fascinating
experimentation will provide some exciting new antenna options for MW DXers,
especially those with modest radios.
73 and Best Wishes,
Gary DeBock (in Puyallup, WA)
**************Snoop, Lil Wayne, Lady GaGa -- land the tix you need for this
summer's biggest tours. Tourtracker.com
(http://www.tourtracker.com/?ncid=emlcntusmusi00000007)
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