The "DX Clams" DXpedition
An Essay written by Gary Thorburn, KD1TE, on DXing with Mark Connelley and Bruce Conti
I joined Bruce Conti and Mark Connelly on a "DX Clams" outing, in search of Seafood and Transatlantic MW DX. You've probably read Mark Connelly's report; Now its time to hear from the junior member of the expedition. We have all marvelled at the extensive and descriptive logs that Mark turns in. If you are like me, you have fired up your receiver on a good night at home and tried to hear some of this stuff. Perhaps like me, you've been disappointed. So over the past couple years, I eagerly joined some mini-DXpeditions, to learn this obscure trade. Two years ago Bruce, Mark, myself, Paul McDonough, Eric Cottrell and maybe a couple others met at Hospital Hill in Rockport MA. With a marginally adequate receiver, but a clearly inadequate antenna, I came home with nothing more than about two European LW broadcasters in my log below 1700 Khz.
They say admitting you need help is the first step. So a year ago, armed with a new Drake R8A, I joined Mark & Bruce at the Rowley marsh site, looking for some help. We strung out two long wires at right angles across the marsh, and Mark tapped my R8A into a splitter which followed his phasing and regen equipment. Think of it! Cable radio, engineered by Mark Connelly. When Mark heard something interesting, he'd shout the frequency and I'd scramble to tune it on my radio too, before he detuned the regen and went looking for something else.
That trip taught me two things. First, that all those MW TAs are really there, if you have a good site and good antennas. At home, 25 miles inland, I had heard hets on the more reliable TA frequencies. But at the shore there are hets everywhere, and audio behind many of them. Second, I learned that tuning a R8A to hear those signals, often separated by only a KHz or two from a local station, requires listening in sideband, with skillful use of narrow filters and the passband control. Techniques that I used on shortwave to improve the listenability of weak or QRM-ridden signals are essential on MW just to hear them at all.
So a month ago I decided to get ready for another Rowley marsh trip. I had built an amplified, tuned 2.5-foot box loop,fitted it to the top of a tripod, and at Mark's suggestion, recently added a simple varactor circuit so I could tune it remotely. I also had picked up a big spool of wire at the last Deerchester flea market. Away from the electrical noise of my home I made a pre-expedition to my back yard. No space for a really long wire, but the loop worked fine separating out domestic stations. Still, the TA split frequencies offered only a few quiet hets.
Which bring us to last Wednesday. Fortified with fried fish and clams, in three vehicles we trekked out the lonely dirt track off rte 1A which ends at a parking lot on the edge of the Parker River National Wildlife Sanctuary. It is a popular site with birders who binocularize from the parking area out into the marsh, or walk further into it along a due-east dirt road which ends at Nelson Island, the last clump of trees before the marsh becomes the Parker River. This minor river drains a few hills that the last glacier deprived of an outlet to the nearby Merrimack. But it expands into a broad estuary between us and Plum Island, probably the most northerly true barrier beach on the east coast.
The Parker River Sanctuary comprises much of the estuary and Plum Island. Beyond Plum Island, the open Atlantic. I parked facing east, and as the dusk settled I walked further eastward down the dirt road into the humid gloom with a spool of 1000 feet of hamfest-grade wire. A technophobe heron took wing, and a few kildeer relayed panic signals among themselves. I strung my wire along the edge of the road, trying to keep it atop the marsh grass for a few inches of height. The spool ran out about a third of the way to Nelson Island, and I returned to the parking lot and set up my other antenna, the amplified remotely tuned loop.
By this time, a few birders were returning from the dusky marsh to their cars, and inquired about our activity. We explained as best we could. Actually, there are many similarities between the two hobbies, both birders and DXers share the urge to log rare catches, and sometimes travel to remote spots with exotic equipment to do it.
Eager newbies in any activity are easily spotted, as they are invariably grossly over equipped but under experienced. I fit this description to a tee. Having removed the center seat from the family mini van, I set up a card table, a homey brass lamp retrofitted to 12-volt operation, prepared my travel coffee pot with ground French Roast, and plugged it into the cigarette lighter. In the aura of a cozy lamp and fresh coffee, I tidied my reference library on the rear seat next to me, and placed the Drake at the center of the table.
As the cigarette lighter was busy with the java, I wired the Drake to a second car battery, and fished two antenna wires and a remote tuning control thru a window. Now for a tape recorder, a few extra C-cells, and a patch cable to R8A. Earlier I did some clandestine grocery shopping, and cleverly hid the loot from my health-conscious wife. From a bag marked "The Twinkie Outlet" I now produced some some unspeakably embarrassing treats. Bruce and Mark, of course, were already deep into the DX, but did I ever have a set up!
Soon the hets came alive with audio, and I was hearing trans-atlantic DX. I was thrilled to hear what Mark and Bruce find to be ordinary logs. I nabbed one pretty clear signal and shouted to Mark, "549, is that Algeria?" He responded yes, and I felt great for about 5 seconds. Then my bubble burst. I hear Mark saying to Bruce, "I think there's something interesting on 549, but its getting totally clobbered by that killer Algerian!"
Using an unterminated wire and a bidirectional loop, I wrestled with more QRM off the back side of my antennas than did Mark with his new phased broadband loop / whip combo which provides a cardioid pattern. The signal level, and reduced QRM that he could produce just blew away the best signal quality I could muster, using an identical Drake receiver. And it all mounts on the top of a compact car, to boot. I think there is a lot of future in this antenna, and I am looking forward to when Mark can publish a complete description of the antennas and associated electronics.
Still, I was quite pleased that my loop did as well as it did. I compared it constantly with the 1000 ft wire, and in the range that it tunes (about 400-1800 kHz) it was usually almost as good as the wire. In particular, my simple amp, comprised of a MC1490 chip and about 3 non-critical discrete parts seems a quiet and effective way to match a loop to a 50-ohm receiver, and I may make further use of it in another antenna.
I made extensive use of the Drake notch filter to knock out adjacent channel hets. Even if a het is only a secondary source of QRM, the Drake notch is so effective, I find it well worthwhile to employ it. How important this is probably varies from person to person, depending on what kind of noise your ears can process.
In conclusion, I would encourage each of you in BADX to look for an opportunity to give a MW expedition a try. For me radio is ultimately an aesthetic experience. If I were able to expound on that eloquently, I think many of you would probably agree, especially if you were fascinated by radio as a child.
Remember those late nights, when your parents thought you were sleeping? But alert and awake, by the warm glow of tubes and a dial lamp, you were connected to distant fading cities, enjoying favorite songs and perhaps a brownie smuggled earlier from the kitchen. Radio is still alive. My Wednesday evening ended late, behind a glowing ersatz dial, enjoying half familiar British rock from Virgin Radio on 1215, and the remains of an illicit sweet snack in the dark night. Still a thrill for me. I thought about the other end of my wire, invisible in a swamp, 1000 feet but transporting me thousands of miles. It was time to go home. I shut down the radio and my ears readjusted to the quiet marsh in front of me. I stepped out into the dank air and followed the wire to the far end of my antenna.
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