LW on the PL-380


jim_kr1s <jkearman@...>
 

Experiments to make the PL-380 play better on LW are encouraging. The MW coil with Hoop Loop  coupling winding were replaced with a 3300-uH coil wound on an FT114-61 toroid. While -61 is not the best mixture for LW and the 1.14-inch-diameter toroid was small for the number of turns required (about 180), it's what I had. With this coil, the PL-380 will tune from 150 to about 510 kHz. The Hoop Loop is coupled through a 15-turn primary. The new coil hangs out the top of the radio, as it's too large to fit inside.

I verified the Hoop Loop was tuning with the radio by holding a G8 tuned to a beacon station it couldn't hear, in the middle of the loop. Then I turned on the PL-380 and tuned it to the same frequency. Even though the G8's antenna won't tune to LW, the station became audible. Tuning the PL-380 up or down from that frequency made the signal on the G8 go away, verifying that the loop was tuning properly. If you have a second receiver that covers the same frequency range, you can do this test with any external antenna tuned by the radio. Even though the new coil won't tune to 530 kHz, R. Enciclopedia was still good copy, as was the ZLS Stella Maris beacon (526 kHz) in the Bahamas. That beacon is a beast; I often hear it on my car radio tuned to 530 kHz.

The mods were complete three hours before sunset yesterday, and right away they paid off. Previously, the only LW station I could hear was a beacon about 20 miles away, on 405 kHz. It sends the number 5 in Morse Code. With the new coil in place and the Hoop Loop plugged in, I logged three new beacons right away. They ranged from SQT in Melbourne, FL, about 80 miles north, to FIS in Key West, about 150 miles south.

After sunset things got even better, as the log below shows. I had good copy on the German-183 kHz, and weak audio on France-216 and Algeria-198, but they weren't good enough to log. Best NDB DX was DDP, San Juan, PR, about 1000 miles. What's interesting and a little ironic is, although I logged two Cayman Islands beacons, I couldn't copy any Cubans! The Caymans are on the other side of Cuba, so this is a mystery. The last time I DXed LW was from the Bahamas, 15 years ago. My best results were at sunrise, but this morning brought no new loggings.

The LC ratio of this modification is pretty high. I've worked out a way to pad the internal tuning varactor with a fixed cap; this means breaking LW into two segments, 150-290 and 250-510 kHz, using two coils (2250 and 750 uH). The Hoop Loop is small for LW, but under the right conditions I think I'll be able to hear European BC stations (which I would much prefer to beacons!). Building the two LW coils and the MW coil into small plastic boxes and installing a connector on the top of the radio, will make it easier to change bands. It will also let me use a larger toroid for the MW coil, which should help a little.

Here's the first night's log:

Date

UTC

kHz

ID

City

S/P/C

04-02-10

2000

405

5

Jupiter

FL

 

2001

332

FIS

Key West

FL

 

2002

275

FPR

Ft Pierce

FL

 

2003

257

SQT

Melbourne

FL

 

2200

526

ZLS

Long Island

Bahamas

 

2250

338

FJ

Ft Pierce

FL

 

2251

260

MTH

Marathon

FL

 

2329

217

CLB

Wilmington

NC

 

2335

183

R Europe 1

Saarlouis

Germany

 

2351

388

AM

Tampa

FL

04-03-10

0033

391

DDP

San Juan

PR

 

0221

198

DIW

Dixon

NC

 

0225

344

ZIY

Georgetown

Cayman Isl.

 

0230

275

BKK

Bonifay

FL

 

0232

329

CH

Charleston

SC

 

0243

415

CBC

Cayman Brac

Cayman Isl.

 

0254

376

ZIN

Matthew Town

Bahamas

 

0255

377

TL

Tallahassee

FL

73,

Jim, KR1S
http://kr1s.kearman.com/ 

Join main@UltralightDX.groups.io to automatically receive all group messages.