PL-380 LW, 4 new countries
Longwave experiments with the PL-380 are going well. Yesterday I tried a variety of coils and parallel capacitors, and settled on a 2650-uH coil and no parallel capacitor. That gave the best results on two beacons that are steady here during the day. This 2650-uH coil tunes up to about 490 uH. BTW, based on dozens of experimental antennas and coils, the total minimum capacitance with an external coil or antenna connected through 2-3 inches of wire seems to be about 30 pF, and may be as high as 40 pF. This matches results obtained by Roy Dyball (where is Roy these days?). It also tells me that 240 uH is the best inductance for a MW antenna or inductor, assuming you want to tune the antenna/inductor across the band. This also matches Roy's results.
It appears that a long ferrite rod with lots of inductance picks up so much more signal, and the higher inductance causes higher voltages to be developed across the coil, even when it isn't resonant, that there is an apparent improvement over the stock antenna, which is pretty poor by any standards. On the low end of the band where the inductance does resonate, the improvement is breathtaking. Assuming you want to DX the full band up to 1700 kHz, it's worth adjusting the inductance to resonate the coil. While the larger coil does outperform the internal antenna, resonating it makes it even better, with only slightly less gain at the low end of the band. It all depends on what part of the band interests you. A really large inductance will tune from about 320-1230 kHz; above 1230 it may still outperform the stock internal antenna or even the stock rod rewound with Litz wire -- but you can do better at the high end if you're willing to give up 320-530 kHz. (A 7.5-inch rod with about 100 turns should do wonders on LW. A 60-turn winding is about right for MW, and you could mount a small switch to add another 40 turns, making the same antenna work on both bands!)
You can tell if the antenna is resonating by holding another portable near the antenna and tuning both radios to the same station. Then change frequencies on the one controlling the antenna and see how the signal strength varies on the second radio. Within a few kHz either way, signal strength should start to drop. If it doesn't change, you know the antenna is not resonating. The advantages of resonating the antenna are, even better signal strengths and better selectivity ahead of the radio, which can help a lot when you have adjacent flamethrowers.
After reworking my LW coil and matching the impedance to my three turn Hoop Loop, I hit LW again last night. Sunset was disappointing, but things started happening about 10:30 pm local time, 0230Z. Lowering the inductance of my coil perked up the high end of the band, to the extent that R Enciclopedia (530 kHz) was very strong. (Even though the coil doesn't resonate at 530. The coil reactance is 8825 ohms, vs 800 ohms for a 240-uH coil. The Stella Maris beacon on 526 kHz was also strong, but I noticed more splatter from Cuba than I get with a MW coil in place, because the larger coil doesn't resonate at 526 kHz, so selectivity is not as good.)
Switching back to LW I started tuning downward in frequency, and in a few minutes logged a new country, with PPA 450 kHz, Puerto Plata, Dominican Republic. http://kearman.com/images/PPA-450.mp3
Moving down to the broadcast section of the band (153-279 kHz), Radio Europa-183 in Germany was coming in well.
They were good copy for about 45 minutes. A little later I logged RTL Luxembourg-234
RMC Info-216 (France)
(you can hear the CLB NDB in Wilmington, NC on 217 kHz underneath) and BBC Radio 4-198, which favored me with a TOH ID
Algeria-252 was audible just before their sunrise, but not strong enough to log. Checking 531, the Algerian heterodyne against Cuba and RVC was weak, so propagation favored more N-S than E-W paths from here last night.
All of the Europeans come in at similar antenna directions. There is a lot of noise here on LW, and I'm hoping that moving the antenna outside will help. It's late in the season, but maybe a few more LW BC stations will fall into the log. Here's last night's log, times in UTC. PL-380 with resonant matching transformer and 3-turn, 23-inch quilting hoop loop antenna , location 100 miles north of Miami, two miles inland.