--- In ultralightdx@..., "jim_kr1s" wrote:
>
> 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.
> http://kearman.com/images/R_Europa_183-kHz_0230Z_040410.mp3
>
>
> They were good copy for about 45 minutes. A little later I logged RTL
> Luxembourg-234
>
> http://kearman.com/images/RTL_234_0320Z_040410.mp3
> ,
>
> France Internal-162
>
> http://kearman.com/images/Fr_Int_162-kHz_0350Z040410.mp3
> ,
>
> RMC Info-216 (France)
>
> http://kearman.com/images/RMC_Info_216-kHz_0402Z_040410.mp3
> <%20http://kearman.com/images/RMC_Info_216-kHz_0402Z_040410.mp3%20>
>
> (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
>
> http://kearman.com/images/BBC_R4_198-kHz_0400Z_040410.mp3
> <http://kearman.com/images/BBC_R4_198-kHz_0400Z_040410.mp3> .
>
> 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.
>
> 0204 450 PPA Puerto Plata DOM 0320 234 RTL
> Beidweiler Luxembourg 0350 162 F Internal Allouis
> France 0355 198 BBC R4 Droitwich UK 0402
> 216 RMC Info Roumoules France
> 73,
>
> Jim, KR1S
> http://kr1s.kearman.com/
>