[IRCA] July 12 Grayland DXpedition and 8' Tuned Passive Loop Performance
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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) 
 
 
                  
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